Molecular Imaging Agents & Techniques

13:30         3202.     A Novel Targeted Iron Oxide Nanocolloid Agent for T1 and T2* Imaging of Fibrin Using Conventional MR Techniques

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Shelton D. Caruthers¹,², Angana Senpan¹, Dipanjan Pan¹, Mike J. Scott¹, Patrick J. Gaffney³, Christian Stehning⁴, Jochen Keupp⁴, Patrick M. Winter¹, Samuel A. Wickline¹, Gregory M. Lanza¹

¹Washington University, St. Louis, Missouri, USA; ²Philips Medical Systems, Andover, Massachusetts, USA; ³St. Thomas' Hospital, London, UK; ⁴Philips Research Europe, Hamburg, Germany

A novel nanocolloid contrast agent with multiple iron-oxide crystals per nanoparticle (1240 &[mu]g Fe per g of emulsion) has been targeted to fibrin clot phantoms and human endarterectomy specimens in vitro. The agent can be visualized as the typical signal dearth on T2* imaging, but also as bright signal on conventional T1-weighted turbo spin echo imaging.  The agent is constrained by size to the vasculature and is predicted to allow imaging to be performed within minutes post-injection.

14:00         3203.     19F Magnetic Resonance Imaging of Increased VCAM-1 Expression in the Kidneys of ApoE-Null Mice Using Targeted  Perfluorocarbon Nanoparticles

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Richard Southworth¹, Junji Chen², Lei Zhang², Megan Kaneda², Huiying Zhang², Samuel Wickline²

¹King's College London, London, UK; ²Washington University School of Medicine, St. Louis, Missouri, USA

Vascular Cell Adhesion Molecule-1 (VCAM-1) is responsible for the tethering of leukocytes to the vascular lumen in early inflammation.  It has been implicated in the pathogenesis of numerous inflammatory diseases, and therefore represents a potentially useful molecular imaging target.  We have developed unique liquid perfluorocarbon nanoparticles which can be functionalised with homing ligands in their outer lipid layer, allowing us to target them to intravascular biomarkers of disease.  These nanoparticles are capable of delivering a targeted payload of over 50,000 Gd atoms, or by virtue of their high 19F content (98% by volume), providing a quantifiable 19F MR signal. Here, we describe their use in specific visualisation and quantification of VCAM-1 expression in the kidneys of atherosclerotic ApoE-/- mice.

14:30         3204.     First Results of an Ex-Vivo Experiment on Human Plaques Using a Contrast Agent Targeting Activated Platelets

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Dominik Paul¹, Constatin von zur Mühlen¹, Julia Möller¹, Timo Spehl¹, Christoph Bode¹, Karlheinz Peter², Dominik von Elverfeldt¹

¹University Hospital Freiburg, Freiburg, Germany; ²Baker Heart Research Institute, Melbourne, Australia

Targeted MRI contrast agents are gaining importance in clinical diagnostic. Here we present an experimental ex-vivo environment for the evaluation of target specific MRI contrast agents on human plaque tissue. The contrast agent consists of microparticles of iron oxide and single-chain antibodies targeting ligand-induced binding sites on activated glykoprotein IIb/IIIa-receptors. Specific target binding resulted in a clear signal drop in high resolution, high field T2 and T2* imaging and was verified by immunohistochemistry. The experimental setup proves to be a promising tool for pre-clinical research on target specific contrast agents.

15:00         3205.     Towards Dual-Mode Imaging of Vulnerable Plaques [Not Available]

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Ben Jarrett¹, Bjorn Gustafsson¹, Angelique Louie¹

¹UC Davis, Davis, California , USA

We have developed dual-mode imaging agents detectable by both MRI and PET for detection and diagnosis of plaque vulnerability.  The probes are targeted to macrophages, whose density correlates with plaque vulnerability.

13:30         3206.     Characterization of Signal Ehnacement Following the  Intraperitoneal Injection of Gadolinium Based Contrast Agents

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Sharon Portnoy¹, Jonathan Bishop¹, Jun Dazai¹, Shoshana Spring¹, R.M. Henkelman¹,²

¹Toronto Centre for Phenogenomics, Toronto, Canada; ²University of Toronto, Toronto, Canada

The objective of this investigation is to determine the enhancement time-course and dosage requirements in mice for intraperitoneally (IP) administered Gadolinium contrast agents.  Although higher doses are required (~2.5 mmol/kg) and enhancement is slightly delayed, results suggest that IP injection may be an effective method for Gadolinium administration.  The relative simplicity of IP contrast administration compared to traditional tail-vein injection makes this method a convenient alternative, particularly in longitudinal studies and high-throughput imaging of large numbers of mice.

14:00         3207.     Fluorine-19 MRI of the Lung: First Human Experiment

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Ursula Wolf¹, Alexander Scholz¹, Maxim Terekhov¹, Kerstin Muennemann¹, Karl Kreitner¹, Christian Werner¹, Christoph Dueber¹, Wolfgang Guenter Schreiber¹

¹Johannes Gutenberg University, Mainz, Germany

As fluorine-19 MRI of the lung appears to be a promising tool for the diagnosis of obstructive lung diseases such as COPD, efforts have been made to improve image quality and to develop a technique which can be safely and effectively used in humans. Since 1984, a lot of animal experiments have been performed using SF6, C2F6, C4F8, C3HF7, and CF4 as contrast gases. Here, we present the data of the first human experiment using up to 78% SF6. This experiment is an important milestone towards the use of fluorine-19 MRI in patients.

14:30         3208.     In-Vivo Ultra-High Resolution Imaging of Small Vessels Using Improved Sensitivity and Long Circulation Time of FeCo-Graphitic Carbon Shell Nanocrystals

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Jin Hyung Lee¹, Sarah Sherlock¹, Masahiro Terashima¹, Hisanori Kosuge¹, Won Seok Seo¹,², Yoriyasu Suzuki¹, Michael V. McConnell¹, Dwight G. Nishimura¹, Hongjie Dai¹

¹Stanford University, Stanford, California , USA; ²Sogang University, Seoul, Republic of Korea

FeCo-Graphitic Carbon Shell Nanocrystals have been recently reported to have an unprecedented high relaxivity with multi-functional capabilities. In this paper, we demonstrate how the improved sensitivity provided by the high relaxivitiy combined with the long circulation time can be used to generate high-resolution in-vivo vessel images.

15:00         3209.     Development of a New Series of Nitroimidazoles Probes for Oxygen Tension (pO₈) Measurement by ¹H Magnetic Resonance Spectroscopy

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Jesus Pacheco¹,², Paloma Ballesteros², Sebastian Cerdan¹, Pilar Lopez-Larrubia¹

¹Instituto de Investigaciones Biomedicas "Alberto Sols"- CSIC, Madrid, Spain; ²Instituto Universitario de Investigacion - UNED, Madrid, Spain

Hypoxia is known to be an important physiological parameter determining tumour progression and malignancy. In this study, we report the synthesis and in vitro evaluation of a new series of nitroimidazolyl derivatives as quantitative pO₈ markers. The NADPH:cytochrome P450 reductase enzymatic systems was found to reduced the probes only under anoxic conditions. Incubation of one of this derivative with C6 cells under different oxygen concentrations depicted clearly visible changes in the ¹H-NMR spectrum at the probe, which depended on the degree of hypoxia.

13:30         3210.     Targeted MR Imaging of CD44-Positive Breast Cancer Stem-Like Cell Phenotype

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Dmitri Artemov¹, Wenlian Zhu¹, Yoshinori Kato¹, Marie-France Penet¹, Farhad Vesuna¹, Zaver Bhujwalla¹, Venu Raman¹

¹Johns Hopkins University, Baltimore, Maryland, USA

Recently, a subpopulation of highly tumorigenic and drug resistant cancer cells was identified in multiple solid tumors, which is currently referred to as cancer stem-like cells.  In breast cancer, these cells are characterized by high level expression of the cell surface receptor CD44 and decreased expression of another marker, CD24..  Here we have developed a CD44-targeted system for MR imaging of breast cancer stem-like cells and demonstrated the MR imaging of CD44 positive MDA-MB-231 human breast cancer cell in vitro.

14:00         3211.     Nanoglobular Gd-DO3A Conjugates as Highly Effective MRI Contrast Agents

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Todd Kaneshiro¹, Eun-Kee Jeong, Dennis Parker, Zheng-Rong Lu¹

¹University of Utah, Salt Lake City, Utah, USA

Novel macromolecular Gd(III) chelates with well-defined nanosizes and globular morphology were synthesized as highly effective MRI contrast agents.  The nanoglobular MRI contrast agents resulted in significant blood and tumor enhancement at a substantially reduced dose, e.g. 10 µmol-Gd/kg.

14:30         3212.     Manganese-Alginate Gels for Controlled-Release of Mn²⁺

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Christian Brekken¹, Ioanna Sandvig¹, Olav Haraldseth¹, Gudmund Skjåk-Bræk¹, Yrr Mørch¹

¹NTNU, Trondheim, Norway

In the present study we aimed at designing alginate beads for controlled release of Mn2+. Both elemental analysis and swelling studies of the alginate gel beads showed great differences in the ion binding properties of alginate to manganese. Dynamic T1-weighted MRI of single alginate beads immersed into NaCl-solution showed that the Mn2+ release rate differed by a factor of up to ~100% between the 4 differently designed beads imaged. The results indicate that nano-fabrication of Mn-alginates can tailor-make biocompatible manganese delivery systems and hopefully help in introducing MEMRI in targeted contrast-enhanced MRI of otherwise toxicity-limited organs, such as the brain.

15:00         3213.     Novel Receptor-Targeted Nanoparticles for MR Imaging and Specific Delivery of Gene Therapy

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Panagiotis Kyrtatos*¹, Michele Writer*, Anthony N. Price¹, Stephen Hart, Mark F. Lythgoe¹

¹Institute of Child Health and Department of Medicine, University College London, London, UK

Multimodal nanoparticles offer a promising application as MRI contrast agents with therapeutic capabilities. Our group is developing a novel gene therapy vector, which utilises an anti-cancer targeting peptide for specific transfection of tumour cells with therapeutic genes. In addition, a Gd3+ moiety has been incorporated for non-invasive real-time monitoring of the delivery. Here we present a pilot in-vitro tumour cell study investigating the MRI properties of the vector, confirming its potential for both specificity of delivery of DNA to the target cells for gene therapy and also providing evidence of the MR contrast enhancement in targeted cells.

13:30         3214.     MR Imaging of Breast Cancer Using the Folate-Receptor Targeted Contrast Agent P1133

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Reinhard Meier¹,², Tobias D. Henning¹, Sophie Boddington¹, Sidhartha Tavri¹, Sandeep Arora¹, Claire Corot³, Ernst J. Rummeny², Heike E. Daldrup-Link¹

¹University of California San Francisco, San Francisco, California , USA; ²Technical University Munich, Klinikum Rechts der Isar, Munich, Germany; ³Guerbet, Paris, France

The purpose of this study was to assess the uptake of the new FR-targeted USPIO P1133 in breast cancers. In vivo studies demonstrated a progressive enhancement of central tumor areas with the FR-targeted USPIO P1133 in FR-positive MDA-MB-231 breast cancers. Corresponding SNR data were significantly higher for P1133 compared to P904B, indicating at least a component of FR-specific enhancement with P1133. The P1133 tumor uptake was not significantly inhibited by FFA in vivo, most likely due to the rapid FFA metabolism in the liver. Thus, the FR-targeted USPIO P1133 provides a significant and specific enhancement of FR-positive MDA-MB-231 breast cancers.

14:00         3215.     Synthesis and Characterization of a Redox- And Light-Responsive MRI Probe [Not Available]

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Chuqiao (Tom) Tu¹, Ryan Ngao¹, Angelique Louie¹

¹UC Davis, Davis, California , USA

We have previously developed a gadolinium contrast agent that reversibly changes relaxivity properties in response to irradiation by different wavelengths of light.  We here demonstrate that the contrast agent can also be modulated by reduction/oxidation.  The mechanism for the relaxivity effects in response to redox appear to differ from the light induced response.

14:30         3216.     Quantitative Molecular Imaging with a Combined Fluorescence Diffuse Optical Tomography and MRI System

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yuting lin¹, Orhan Nalcioglu², Gultekin Gulsen²

¹University of California, Irvine, California , USA; ²University of California, Irvine, California , USA

An ideal molecular imaging technique should have both high sensitivity for molecular probes and also provide high-resolution images. Our solution to this demanding requirement is to employ a multimodality imaging strategy. In this study, we show the feasibility of using a combined MRI and optical fluorescence imaging approach to quantitatively resolve the fluorescence contrast agent concentration. The true fluorophore concentration was recovered only if the MRI anatomical information was employed.

15:00         3217.     Real-Time Feedback Paradigm for Functional and Metabolic Imaging Using a Combined PET/MR Scanner: Proof of Concept

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Thomas Sheung Chee Ng¹,², Daniel Procissi¹, Andrey Demyanenko¹, Yibao Wu³, Ciprian Catana⁴, Simon R. Cherry³, Andrew A. Raubitschek⁵, Russell E. Jacobs¹

¹California Institute of Technology, Pasadena, California, USA; ²University of Southern California, Los Angeles, California , USA; ³University of California,  Davis, Davis, California , USA; ⁴Massachusetts Gener

Positron Emission Tomography (PET) and Magnetic Resonance (MR) offer complementary functional and anatomic information that provide unique windows into biological processes. As well as integrating images in space and time, the combined PET/MR scanner offers the potential to perform real time analysis of multi-modal data that can feedback to direct further studies in a single imaging session. We demonstrate the feasibility of this paradigm. Mice implanted with tumor cells were imaged simultaneously with PET/MR. Functional data derived from the PET was used as a basis for 1H-MR spectroscopy studies, demonstrating metabolic heterogeneity within a tumor cell mass.

MRS of Cells, Body Fluids

13:30         3218.     [3-¹³C]Pyruvate: Useful Alternative to Labeled Glucose for in Vitro Metabolic Studies in Primary Mouse Hepatocytes

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Sven Gottschalk¹, Michaela Hohnholt², Dieter Leibfritz², Marc Bilodeau¹, Claudia Zwingmann¹

¹University of Montréal, Montréal, Canada; ²University of Bremen, Bremen, Germany

Application of stable isotope labeling in vitro is a powerful method to study metabolic pathways and fluxes. We applied [3-¹³C]pyruvate on primary mouse hepatocyte cultures to establish labeled pyruvate for metabolic studies and flux analysis in this cellular model. Our results show: [3-¹³C]pyruvate was metabolized by lactate dehydrogenase, alanine-/aspartate-aminotransferase, PC, PDH and subsequent metabolic pathways through the TCA-cycle. Considering that almost no ¹³C-NMR studies in isolated hepatocytes have been performed so far, labeled pyruvate will provide an important physiological substrate to assess hepatocellular pathways and the de novo synthesis of metabolites in these cells under normal and pathological conditions.

14:00         3219.     A Versatile NMR-Compatible Bioreactor for Alginate-Encapsulated Liver Cells

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Rex Errol Jeffries¹, Kayvan R. Keshari, Chris Seagle, Peter Pediaditakis, Michael P. Gamcsik, John Kurhanewicz, Jeffrey M. Macdonald

¹University of North Carolina, Chapel Hill, USA

Synopsis: A remodeled NMR-compatible bioreactor was used with electrostatic alginate encapsulation of hepatocytes to create a bioartificial liver ultimately designed for metabolomic studies. The 500 μm diameter spherical encapsulates are well perfused and permit the use of 20% oxygen rather than the standard 95% oxygen. The 31P NMR spectra from a rat liver cell line, JM1, and primary rat hepatocytes were compared to oxygen uptake rates for bioenergetics.

14:30         3220.     Metabolism of Colonic Mucosa in Patients with Ulcerative Colitis (UC) and Crohn’s Disease (CD): An NMR Study

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B Krithika¹, S Kumar¹, R R. Singh¹, Uma Sharma¹, V Ahuja¹, G K. Makharia¹, N R. Jagannathan¹

¹All India Institute of Medical Sciences, New Delhi, India

In vitro NMR spectroscopy demonstrated significant differences in the concentration of amino acids (isoleucine/leucine/valine, glutamic acid + glutamine, alanine), membrane components (choline, glycerophosphorylcholine, myoinositol), glycolytic product (lactate) in patients with active state of ulcerative colitis (UC) and Crohn’s disease (CD) compared to controls indicating a decreased protein and carbohydrate metabolism.  In the remission state, levels of most of the metabolites were similar to controls. A significant difference in the concentration of formate was observed between patients with active states of UC and CD suggesting its potential as a biomarker for distinguishing UC and CD.

15:00         3221.     Cellular Metabolism and Apoptosis – Dexamethasone, a Promising New Candidate to Intervene on the Metabolic Level

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Sven Gottschalk¹, Michaela Hohnholt², Dieter Leibfritz², Claudia Zwingmann¹, Marc Bilodeau¹

¹University of Montréal, Montréal, Canada; ²University of Bremen, Bremen, Germany

We have recently shown that the initial phase of the apoptotic process is associated with alterations in specific glucose metabolic pathways. The synthetic glucocorticoid Dexamethasone is known for its anti-apoptotic effects and impact on glucose metabolism (in particular, anaplerosis and gluconeogenesis). We therefore characterized the effects of Dexamethasone on hepatocellular metabolism with multinuclear NMR-measurements. Our results further support the strong relationship noted between changes in cellular metabolism and apoptosis. This paves the way toward the therapeutic modulation of cell metabolism in order to influence upon cell survival/death particularly in the context of liver injury.

Cell Labelling & Tracking

13:30         3222.     In Vivo Imaging of Endogenous Neural Stem Cells Labelled with a Ferumoxide-Polycation Complex Using a Low Field System

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Rachael Dobson¹,², Patrizia Ferretti¹, Mark Lythgoe¹

¹University College London, London, UK

Adult neural stem cells (NSC) migrate towards the olfactory bulb and differentiate into neurons. Ferumoxide-based contrast agents have been used to track the migration of exogenously-labelled NSC, there are limited methods that allow for longitudinal tracing of endogenous neural stem cells using MRI. In this study, two MRI contrast agents were used to label the endogenous population of NSC and neuroblasts in situ in the subventricular zone.  Cell labelling and T2* contrast were assessed up to 28 days post-labelling using a low-field system.  Cell migration was observed in vivo and ex vivo, and histology confirmed labelling of migrating neuroblasts.

14:00         3223.     Quantification of Cell Trafficking in Vivo Using Magnetically Sensitive Histograms

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Christopher M. Long¹, Hyam I. Levitsky¹, Jeff W.M. Bulte

¹Johns Hopkins University School of Medicine, Baltimore, Maryland, USA

Quantification of dendritic cell migration to lymph nodes in vivo is critical for evaluating the efficacy of tumor vaccines.  We developed a new method based on magnetically sensitive histograms and cell-cell transfer of SPIO particles in vivo.   It was found to correlate exceptionally well with ex vivo cell counts after magnetically activated cell sorting  The method may be used to monitor the biological variability associated with cancer vaccination and to evaluate the efficacy of immunoadjuvants.

14:30         3224.     In Vivo Stem Cell Tracking Using Magnetic Resonance Imaging in the Rat Genitalia of a Radical Prostatectomy Model
[Not Available]

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Young Taik Oh¹, Jang Hwan Kim¹, Yong-Min Huh¹, Myeong-Jin Kim¹, Jin-Suck Suh¹

¹Yonsei University College of Medicine, Seoul, Republic of Korea

Erectile dysfunction is a major complication after radical prostatectomy for prostate cancer. There have been vigorous trials for improving erectile dysfunction but no satisfying method until now. Previous reports have shown that stem cell injection improved erectile function in a rat model erection dysfunction. However, they used the immunohistochemical stain for the evaluation of stem cell. A reliable in vivo imaging method to localize transplanted cells and monitor their restorative effects will enable a systematic investigation of cell therapy. Our results showed that in vivo stem cell tracking using MR imaging in a rat model of radical prostatectomy was feasible.

15:00         3225.     Comparison of Different Iron-Oxide Agent Detection Methods Using a Single Dataset

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Gopal Varma¹, Richard Tavare¹, Hannes Dahnke², Stephen Keevil¹, Tobias Schaeffter¹

¹King's College London, London, UK; ²Philips Research Laboratories, Hamburg, Germany

Detection of super-paramagnetic iron oxide can be achieved at varying sensitivities through its inherent negative contrast or by positive contrast methods. A single multi-echo dataset is used to compare T₈* weighted imaging, R₈* mapping, and positive contrast methods. In our study this includes inversion recovery on-resonance (IRON), gradient dephasing (“white marker”), and susceptibility gradient mapping (SGM). T₈* images are found to be most sensitive to the smaller concentrations at short echo times (TEs), but high sensitivity of SGM and T₈* imaging suggests a combination of these two methods is ideal. Data acquired for T₈* images and SGM at 2 different TEs to address different concentrations would provide a more sensitive differentiation to the background.

13:30         3226.     Stem Cell Treatment for Peripheral Arterial Disease - Comparison of Plain and Encapsulated X-Ray Visible Mesenchymal Stem Cell Transplants

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Dorota A. Kedziorek¹, Wesley D. Gilson², Kenyatta Cosby¹, Matthias Stuber¹, Bradley P. Barnett¹, Royston C. Boston³, Grigorios Korosoglou⁴, Bernard E. Kohl¹, Gary Huang¹, Brady Sieber¹, Aravind Arepally¹, Jeff W.M. Bulte¹, Lawrence V. Hofmann⁵, Dara L. Kraitchman¹

¹Johns Hopkins University, Baltimore, USA; ²Siemens, Baltimore, USA; ³University of Pennsylvania, Kennet Square, USA; ⁴University of Heidelberg, Heildelberg, Germany; ⁵Stanford University, USA

The resented work comapares plain and encapsulated Mesenchymal Stem Cell therapy in Peripheral Arterial Disease model. Non-invasive imaging demonstrated a more robust angiogenic response with encapsulated MSCs, while "naked" MSCs can incorporate into the vessel walls.

14:00         3227.     Micrometer-Sized Particles of Iron Oxide (MPIOs) Enhanced Cardiac Imaging to Potentially Monitor Inflammatory Cells Infiltration in a Murine Model of Myocardial Infarction

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Yidong Yang¹,², Ben Waghorn¹,², Yuhui Yang¹, Brianna Klein¹, Nathan Yanasak¹, Tom C-C. Hu¹,²

¹Medical College of Georgia, Augusta, Georgia, USA; ²Georgia Institute of Technology, Atlanta, Georgia, USA

Inflammatory process plays an important role in myocardial injury and the subsequent recovery. In this study, we examined cell mobilization due to myocardial infarction post injection of micrometer-sized particles of iron oxide (MPIOs). MRI was performed to potentially visualize the migration and trafficking of inflammatory cells as well as to provide quantitative information. This technique indicates potential to track disease progression in a preclinical model of myocardial injury.

14:30         3228.     In Vitro MR Thermometry on Magnetically Heated Iron Oxide Labeled Stem Cells

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Daniel Haddad¹, Jochen Lorenscheit², Markus Hildenbrand¹, Meike Weber², Regina Ebert², Peter Michael Jakob¹,²

¹MRB Research Center Magnetic-Resonance-Bavaria, Würzburg, Germany; ²University of Würzburg, Germany

Iron-oxide nanoparticles are commonly used as MR markers to label and track (stem) cells. Magnetic particle heating (magnetic field hyperthermia) can be used to heat the iron-oxide particles and thus the iron labeled stem cells. A proof-of-principle in vitro study shows that MR thermometry can be used to visualize the spatial and temporal heat distribution with high accuracy in the vicinity of iron-oxide labeled stem cells that were heated outside the MR spectrometer via magnetic particle heating. Since the heating capacity depends on the composition and structure of the material of interest, different types of iron-oxide particles yield different heating rates. The heating rates can also be controlled by varying the amount of iron-oxide incorporated in the cells.

15:00         3229.     Tracking of Spio Labeled Natural Killer Cells to Epcam Positive Prostate Cancer with Mr Imaging

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Reinhard Meier¹,², Sidhartha Tavri¹, Tobias D. Henning¹, Winfried S. Wels³, Rick Baehner¹, Ernst J. Rummeny², Heike E. Daldrup-Link¹

¹University of California San Francisco, San Francisco, California , USA; ²Technical University Munich, Klinikum Rechts der Isar, Munich, Germany; ³Chemotherapeutisches Forschungsinstitut, Frankfurt, Germany

Development and optimization of a technique for labeling of human natural killer (NK) NK-92 cells and genetically engineered NK-92-scFv(MOC31)-zeta cells, targeted to the Ep-CAM (epithelial cell adhesion molecule) on prostate cancer cells, with superparamagnetic iron oxides (SPIO). SPIO labeled NK cells were injected intravenously into rats with implanted Ep-CAM positive prostate cancers and the accumulation of the SPIO labeled NK cells in prostate tumors could be monitored with a non-invasive magnetic resonance (MR) imaging technique.

13:30         3230.     Study on the Magnetic Relaxation of Superparamagnetic Nanotubes as Magnetic Resonance Imaging Contrast Agent

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xia Bai¹, sang jun Son¹,², shixiong Zhang¹, wei Liu³, elaine k. Jordan⁴, joseph a. Frank⁴, Thirumalai Venkatesan¹, Sang Bok Lee¹

¹university of maryland college park, college park, Maryland, USA; ²Kyungwon University, Republic of Korea; ³Philips Research North America, Briarcliff Manor, New York, USA; ⁴National Institutes of Health, Bethe

This work describes the synthesis of magnetic nanotubes (MNTs) which is silica nanotube (SNT)/magnetic iron oxide nanoparticle (MION) composite with MIONs loaded in SNTs. This unique structure combines the easy chemistry for differential functionalization of the inner and outer surfaces of SNTs with the superparamagnetic characteristics of MIONs. The MNTs had well-controlled dimensions and retained a high saturation magnetization. It was proved that MNTs worked as an effective T2 magnetic resonance (MR) contrasting agent. The in vitro cell labeling was effective without showing significant cytotoxicity. Our results indicate that MNTs could be an ideal candidate for image-guided drug delivery.

14:00         3231.     MRI Detection of the Migrating Neuronal Precursors in Normal and Hypoxic-Ischemic Neonatal Rat Brain by in Vivo Cell Label with MPIO

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Jian Yang¹,², Jian Xin Liu³, Gang Niu², Yong Liu³, Ed X. Wu⁴

¹Department of Electrical and Electronic Engineering, The University of Hong Kong , Hong Kong, People's Republic of China; ²The First Hospital of Xi'an Jiaotong University, Xi'an, People's Republic of China; ³The School of

In this study,10-day-old normal rats (n=6) and hypoxic-ischemic (H-I) neonatal rats (n=6) were injected with the micronsized iron oxide particles (MPIOs) into the anterior lateral ventricle. 2D and 3D gradient echo MRI was performed with a 7T animal scanner in hour 3, day 3, day 7 and day 14 after the MPIOs injection. Then animals were sacrificed for double staining with iron and mature neurons. In normal neonatal rat brain, the migrating pathway of the endogenous neural progenitor cells (NPCs) with MPIO is mainly along the rostral migratory stream to the olfactory bulb. In H-I neonatal rat brain, the migration of endogenous NPCs with MPIO is mainly toward injured boundary. MRI can facilely detect the above migrations in 2 weeks. Therefore, in vivo magnetic cell labeling of endogenous NPCs with MPIO and subsequently non-invasive, serial MRI monitoring should open up a new approach to probe into the mechanism of cell migration in the developmental brain under physiological and pathologic states.

14:30         3232.     Quantitative Assessment of Magnetically Labeled Luciferase Positive Cells Using Multimodality Imaging

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April M. Chow¹,², Kwan Man¹, Jerry S. Cheung¹, Tracy Y. Chow¹, Ed X. Wu¹

¹The University of Hong Kong, Pokfulam, Hong Kong

Cellular imaging using magnetically labeled luciferase positive cells with multimodality imaging has found numerous biological applications. However, studies only involve imaging dual-labeled cells, tracking their migrations without quantification of local density of the dual-labeled cells. Quantitative analysis of cells after transplantation may allow more accurate assessment of cell delivery and subsequent distribution and migration, which can lead to more effective monitoring and optimization of therapeutic paradigms. In this study, we demonstrated that dual-labeled cells exhibited excellent linear correlations between cell concentration with photon flux and &[Delta]R2* in vitro, illustrating that quantitative assessment of dual-labeled cells can be achieved.

15:00         3233.     Comparison of 2 Different Tumor Cell Labeling Techniques for in Vitro MRI Characterization with New Iron Oxide Particles

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Olaf Saborowski¹, Francesco Santini², Melpomeni Fani³, Philippe Robert⁴, Sebastien Ballet⁴, Jean Sebastien Raynaud⁴, Robin Santus⁴, Johannes Froehlich³, Klaus Scheffler², Georg Bongartz³, Helmut R. Maecke³

¹University Hospital Basel, Basel , Switzerland; ²University Basel/University Hospital, Basel, Switzerland; ³University Hospital Basel, Basel, Switzerland; ⁴Guerbet Group, Aulnay-Sous-Bois, France

Iron oxide particles (SPIO and USPIO) are widely used for MRI-based cell labeling and tracking because they can be loaded on cells by simple protocols and provide high image contrast due to their large susceptibility effect. We compared 2 different cell labeling models (AGAR and Ficoll) in human KB cells. Both presented cell labeling methods (AGAR and Ficoll model) are feasible for in vitro MR characterization of KB tumor cells at 1.5, 2.35 and 3T. Ficoll method is easier to perform because it does not need a heating procedure for preparation without air bubbles as compared to AGAR method.

13:30         3234.     Longitudinal Tracking and Quantification of T Cells Using in Vivo 19F MRI [Not Available]

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Mangala Srinivas¹, Michael S. Turner², Penelope A. Morel², Jelena M. Janjic¹, David H. Laidlaw³, Eric T. Ahrens¹,⁴

¹Carnegie Mellon University, Pittsburgh, Pennsylvania, USA; ²University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA; ³Brown University, Providence, USA; ⁴Pittsburgh NMR Center for Biological

¹⁹F MRI was used to track T cells in a murine model of acute inflammation for up to 21 days. Quantification of total ¹⁹F signal in the DLN, and hence apparent cell numbers, from the in vivo data showed 2.1x10⁶ ± 9x10⁵ apparent cells at day 2 and 3.6x10⁶ ± 9x10⁵ at day 7 post-transfer in the draining lymph node. The murine inflammation model can be applied to study the effect of therapeutics on T cell trafficking. The in vivo ¹⁹F platform developed can readily be extended to other cells types including, immunotherapeutics or stem cells.

14:00         3235.     A Novel Bimodal Fluorescent and Paramagnetic Lipid for Cell Labelling and Tumour Magnetic Resonance Imaging

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Nazila Kamaly¹, Tammy Louise Kalber¹, Jimmy D. Bell¹, Michael R. Jorgensen¹, Andrew David Miller¹

¹Imperial College London, London, UK

A novel bimodal fluorescent and paramagnetic lipid, Gd.DOTA.Rhoda.DSA was synthesised. Cationic and neutral PEGylated bimodal liposomes were formulated for cell labelling and tumour imaging respectively. Effective IGROV-1 (human ovarian carcinoma) cell labelling was demonstrated in vitro post incubation of cells with the cationic liposome formulations containing Gd.DOTA.Rhoda.DSA. The enhanced permeation and retention (EPR) effect of tumour tissue was exploited post-injection of the neutral PEGylated liposomes in mice to image IGROV-1 xenografts. Tumour T1 values were reduced 14-24 h post-injection of the bimodal liposomes by a substantial 65%. These MRI findings were supported by fluorescence findings co-validating the presence of the bimodal liposomes/lipid within tumour tissue.

14:30         3236.     Bimodal Intracellular Nanoparticles Based on Quantum Dot Technology for High Field MR Microscopy at 21.1 T

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Jens Thorvald Rosenberg¹,², Joshua M. Kogot¹, Goeffery F. Strouse¹, Samuel Colles Grant¹

¹The Florida State University, Tallahassee, USA

A bimodal contrast agent for the intracellular transfection of mammalian cells has been optimized for high magnetic field MR imaging at 21.1 T. With a fluorescent InP/ZnS quantum dot as a substrate, a peptide-bound lanthanide (Dy³⁺) component has been added to generate MR contrast. The CAAKA–DOTA-Ln³⁺-Qdot agent displays strong MR contrast enhancement for all relaxation mechanisms, but the strongest contrast for intracellular loading is seen with T2/T2* weighting. Utilizing this agent, Chinese Hamster Ovary (CHO) cells were transfected, with MR and confocal images displaying contrast enhancement and the intracellular localization of nanoparticles.

15:00         3237.     ¹⁹F NMR Molecular Imaging: Cell Labeling With Emulsified Perfluoro-15-Crown-5-Ether

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Samir Mulla-Osman¹, Henrike Goetze², Ute Bommerich³, Johannes Bernarding

¹University of Magdeburg, Magdeburg, Germany; ²University of Magdeburg, Germany; ³Leibniz Institute for Neurobiology, Germany

Monitoring ¹⁹F-labelled cells is an important new technique to evaluate in vivo the fate of implanted cells such as in stem cell therapy. The use of ¹⁹F-marker substances such as perfluorocarbons (PFC) has been explored by ¹⁹F spectroscopy and magnetic resonance imaging (MRI) for cell tracking. We present first results of single volume selective spectroscopy of fibroblasts, which have been labeled with perfluoro-15crown-5-ether (PFCE) emulsion.

MRS Methodology

13:30         3238.     MEGA-Editing of  Spermine/Spermidine in Healthy Human Prostates Using External Phased-Array Coil Assembly

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Michael Albert Thomas¹, S.Sendhil Velan², Saadalah Ramadan³,⁴, Nagarajan Rajakumar¹, Daniel J. Margolis¹, Maria Ana Gomez¹, Steve S. Raman¹, Carolyn E. Mountford³,⁴

¹UCLA, Los Angeles, California , USA; ²West Virginia University, Morgantown, West Virginia, USA; ³Brigham and Women's Hospital, Boston, Massachusetts, USA; ⁴Harvard Medical School, Boston, Massachusetts, USA

Polyamines such as spermidine and spermine play a critical role in cell proliferation and differentiation in cancer. Overlap of metabolite resonances is a major concern in conventional one-dimensional (1D) MR Spectroscopy (MRS), hence spectral-editing techniques either based on signal subtraction or multiple-quantum filter have been proposed and tested in human brain in vivo. A goal of this work was to implement a MEGA-based spectral editing sequence on a 3T MRI scanner, to optimize the technique using prostate phantom, and to evaluate the feasibility of detecting spermine/ spemidine in healthy human prostates using an external phased-array matrix coil assembly.

14:00         3239.     Optimized MRS of Neurotransmitters: How Far Do You Need to Go?

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Paul Mullins¹,², Hongji Chen², Jing Xu², Arvind Caprihan², Charles Gasparovic²,³

¹Bangor University, Bangor, UK; ²The MIND Research Network, Albuquerque, New Mexico, USA; ³University of New Mexico, Albuquerque, New Mexico, USA

Standard and optimized MRS sequences for the detection of Glutamate and other neurotransmitters are compared for test re-test reliability.

14:30         3240.     High Speed Multi-Voxel Thermography with Free Induction Decay Echo Planar Chemical Shift Imaging

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Matthew A. Neimark¹, Scott Henneman², Yingli Yang², Jae Choi², Angelos Aristeidis Konstas³, Melvyn B. Ooi, Hamed Mojahed², Andrew F. Laine², John Pile-Spellman², Truman R. Brown²

¹Columbia University, New York, New York, USA; ²Columbia University, New York, USA; ³Massachusetts General Hospital, Boston, USA

In this study, we present a fast method of performing spectroscopic imaging using free induction decay echo planar chemical shift imaging (FID EP-CSI).  This technique was performed on a phantom made up of Ringer’s lactate and 10 mM NAA.  The phantom was cooled from 38 to 29°C while temperature was continuously monitored, and 13 FID EP-CSI acquisitions were performed.  Each acquisition was 28 seconds.  This is 12 times faster than conventional CSI. For voxels in a central region, the overall regression for  NAA-H₈O difference (δ_NAA-H8O)  vs. temperature (±95% confidence intervals) was T=(100.67±1.07)δ_NAA-H8O+300.36±2.86 (R2=0.9967; rms=0.16°C).

15:00         3241.     Fully Automated Shimming for High Lipid Regions Using Phased Arrays at 3T

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Gamaliel Isaac¹, Jeremy jeremy.magland@upenn.edu Magland, Hoby Patrick Hetherington²

¹University of Pennsylvania, Philadelphia, Pennsylvania, USA; ²Yale University, New Haven, Connecticut, USA

We have developed a robust fully automated method for shimming regions of the body with high lipid content which is compatible with phased array detection. The method utilizes multi evolution delay B0 maps to generate high accuracy while retaining a large bandwidth for poor starting homogeneity. The method includes an embedded Dixon image to identify fat and water content such that the chemical shift due to lipid is corrected for allowing for the use of arbitrary evolution times. To demonstrate the method we have applied it to shim the human calf at 3T on a Siemens Trio system.

13:30         3242.     SVD 8-Channel Coil Combine for 2D Chemical Shift Imaging (CSI) MRI

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Mithun Diwakar¹, Mingxiong Huang¹,², Roland R. Lee¹,², Rebecca J. Theilmann¹

¹UCSD, La Jolla, California , USA; ²VA San Diego Healthcare System, San Diego, California , USA

This work describes a novel method for combining 2D Chemical Shift Imaging (CSI) data recorded by 8 independent phased array coils (8-channel GE head coil).  Singular Value Decomposition (SVD) is a form of dominant mode analysis that can be used to combine time decay signals.  The work was carried out on a phantom containing physiologic concentrations of key metabolites found in the brain (NAA, Ch, Cr). The advantages of SVD over conventional methods of combining signals from multiple coils include preservation of phase-information, automatic zero-order phasing, and no need of a priori information.

14:00         3243.     Improved Spectral Quality Through Enhanced Shimming on a Clinical Platform at 3T and 7T

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Ralf Mekle¹,², Giulio Gambarota¹, Vladimir Mlynarik¹, Rolf Gruetter¹,³

¹Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland; ²University of Lausanne, Lausanne, Switzerland; ³Universities of Lausanne and Geneva, Lausanne and Geneva, Switzerland

Reliable localized shimming is an essential prerequisite for obtaining high-quality MR spectra, especially at higher fields (≥3T). For the first time, the fast automatic shimming technique by mapping along projections (FASTMAP) and its descendant FASTESTMAP were implemented on a clinical platform of a 3T and a 7T system. In vivo proton spectra from various brain regions were acquired and showed excellent quality due to the enhanced local field homogeneity resulting from improved shimming with FASTMAP/FASTESTMAP that translated into reduced water and metabolite linewidths at both field strengths.

14:30         3244.     Application of Forward Linear Prediction Method to High-Resolution NMR Spectra in Inhomogeneous Fields

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Hai Feng¹,², Zhiwei Chen¹, Shuhui Cai¹, Xiaohong Wang¹, Ji Feng³, Zhong Chen¹

¹Xiamen University, Xiamen, People's Republic of China; ²Institute of Physics, Chinese Academy of Sciences, Beijing , People's Republic of China; ³Institute of Physics, Chinese Academy of Sciences, Beijing, People's Republ

The forward linear prediction (LP) method was applied to deal with 2D intermolecular double quantum coherence spectra from inhomogeneous fields. The results show that compared to normal discrete Fourier transform, the use of forward LP extrapolation can shorten sampling time by a factor of eight or more at the same level of sensitivity and resolution. It can effectively extend the data sets acquired from inhomogeneous fields even for shorter data records and lower signal-to-noise ratio.

15:00         3245.     High-Quality MR Spectroscopy of the Human Brain with Full Signal Intensity at Echo Times Below 6 Ms on a Clinical Platform at 3T and 7T

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Ralf Mekle¹,², Vladimir Mlynarik¹, Giulio Gambarota¹, Martin Hergt³, Gunnar Krueger³, Rolf Gruetter¹,⁴

¹Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland; ²University of Lausanne, Lausanne, Switzerland; ³Siemens Medical Solutions-CIBM, Lausanne, Switzerland; ⁴Universities of Lausanne and Geneva, Lau

The implementation of the spin echo full intensity acquired localized (SPECIAL) spectroscopy technique on a clinical platform was taken to the next level by combining interleaved water suppression (WS) and outer volume saturation (OVS), optimized sequence timing, and large B1 fields producing coils in addition to improved shimming. High-quality single voxel spectroscopy (SVS) data of the human brain were acquired at TEs below 6 ms on 3T and 7T systems. The high SNR of the spectra enabled reliable metabolite quantitation at both field strengths. Moreover, the enhanced sensitivity at the higher B0 field allowed a twofold reduction in scan time.

13:30         3246.     Automating Brain Tumour Classification Using High Resolution Magic Angle Spinning Data

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Jean-Baptiste Poullet¹, Daniel Monleon², M. Carmen Martinez-Bisbal³,⁴, Bernardo Celda³,⁴, Sabine Van Huffel⁵

¹Katholieke Universiteit Leuven , Leuven, Belgium; ²Fundación Investigación Hospital Clínico Universitario Valencia, Valencia, Spain; ³University of Valencia, Spain; ⁴Networking Research Center on Bioengineering

The limited success of in vivo MRS to classify some brain tumor types tends to encourage the use of other data types. Thanks to their narrow line widths and their large signal-to-noise ratios, high resolution magic angle spinning (HR-MAS) data provides much more information than in vivo MRS. Since biopsy extraction is a routine procedure in the clinical practice, incorporating HRMAS in the decision system is a reasonable solution to improve brain tumor diagnosis. This study propose a fully automated procedure to classify HR-MAS spectra.

14:00         3247.     Proton Decoupled ³¹P MRS of Head and Neck Tumors in Vivo at 1.5T and 3T [Not Available]

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Sungheon Kim¹, Sanjeev Chawla¹, Laurie A. Loevner¹, Harry Quon¹, Eric J. Sherman¹, Gregory S. Weinstein¹, Harish Poptani¹

¹University of Pennsylvania, Philadelphia, USA

The purpose of this study was to implement proton decoupled ³¹P MRS at 3T for assessing smaller tumors and to investigate its feasibility in predicting treatment response in head and neck tumors. Proton decoupled ³¹P MRS data were acquired from eleven patients who were treatment naïve. Substantial increase in SNR with smaller voxel sizes was achieved at 3T as compared to 1.5T.  In a small cohort of patients, studied at 1.5T, ³¹P MRS studies partial responders exhibited higher PME/_βNTP and PDE/_βNTP ratio than complete responders indicating the potential of ³¹P MRS in prediction of treatment response.

14:30         3248.     In Vitro Metabolites Limit of Detection by Localised NMR Spectroscopy Using Micro Coils

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Nicoleta Baxan¹, Aziz Kadjo¹, Guillaume Pasquet¹, Jean-François Chateaux¹, André Briguet¹, Pierre Morin¹, Danielle Graveron-Demilly¹, Latifa Fakri-Bouchet¹

¹Université Lyon1, Villeurbanne, France

We present a new concept of receiver planar micro coil fabricated by electroplating technique. The innovative part of this work concerns:

- Implemented MR instrumentation at micro-scale,

- Restricted volumes detection by MR spectroscopy and imaging.

The spectrum of a solution containing eleven MR-observable 1H metabolites in human brain (50 mM) is presented, the concentration limit of detection (LODc) for the Choline and NAA case are estimated at 3.3 mM and 10.4 mM respectively. The measurements reproducibility was established using six micro coil prototypes.

The micro coils performance improvement open the way to highly spatially resolved explorations on animal model.

15:00         3249.     Diffusion-Weighted 1H NMR Single Voxel Spectroscopy at 3T and 7T

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Daniela Wagegg¹, Ralf Lützkendorf², Wolfgang Dreher³, Claus Tempelmann⁴, Jörg Stadler⁵, Johannes Bernarding²

¹Institute for Biometry and Medical Informatics, Medical  Faculty, University of Magdeburg, Magdeburg, Germany; ²Institute for Biometry and Medical Informatics, Medical Faculty, University of Magdeburg, Magdeburg, Germany

We implemented Diffusion-weighted Single Voxel Spectroscopy on a 3T- and 7T-MR-Scanner. The Sequence was based on a STEAM-Sequence. The DW-gradients where applied simultaneously in each direction. In phantom studies, this allowed the calculation of the ADC values of several brain metabolites successfully.

Non-Proton MRI

13:30         3250.     Sodium Mapping in Focal Cerebral Ischemia in the Rat by Quantitative ²³Na MRI

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Victor E. Yushmanov¹, Boris Yanovski¹, Alexander Kharlamov¹, George LaVerde², Fernando E. Boada², Stephen C. Jones¹

¹Allegheny-Singer Research Institute, Pittsburgh, Pennsylvania, USA; ²University of Pittsburgh, Pittsburgh, Pennsylvania, USA

²³Na twisted projection MRI was validated as a quantitative technique to assess local brain sodium concentration ([Na⁺]_br) every 5.3 min after MCAO.  The MRI protocol included a 0.4-ms echo-time, a B₁ mapping, and 0-154 mM NaCl calibration standards.  [Na⁺]_br values were obtained by MRI and flame photometry in exactly the same ROIs of ~0.5 mm³ size.  The Bland-Altman comparison of the two techniques in normal and ischemic cortex and caudate putamen of seven rats yielded a mean bias and limits of agreement of -4%±42% of average.  A linear increase in [Na⁺]_br was observed at 1-6 hours after MCAO.

14:00         3251.     Sodium MRI with Triple Quantum Filter and Inversion Recovery at 7T

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Guillaume Madelin¹, Niels Oesingmann², Glyn Johnson¹, Alexej Jerschow¹, Matilde Inglese¹

¹New York University, New York, New York, USA; ²Siemens Medical Solutions USA, New York, New York, USA

This study demonstrates the feasability of Sodium MRI at 7T with Triple Quantum Filter (TQF) and Inversion Recovery (IR) in differentiating mobile vs. less mobile 23Na nuclei in phantoms. The combination of TQF and IR can give complementary informations about the sodium environment and allow a better differentiation of the intracellular and extracellular compartments in biological tissues. Future studies will focus on TQF and IR 23Na MRI on human brain in vivo at 7T in order to assess the intracellular sodium concentration, with the goal of localizing pathologies.

14:30         3252.     Clean Separation of Bound vs. Free Sodium by ²³Na Inversion Recovery

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Peng Rong¹, Ravinder R. Regatte², Alexej Jerschow¹

¹New York University, New York , New York, USA; ²New York University, New York, New York, USA

Monitoring the bound sodium pool often allows one to characterize tissue disorders, such as osteoarthritis, or cell dysfunction. Separation methods have been used based on residual quadrupolar interactions, or slow molecular tumbling. In the current study, we demonstrate the feasibility of employing the inversion recovery (IR) sequence to selectively detect the bound or the free sodium pools in cartilage tissue. The advantages of this method are its simplicity, the ability to selectively detect either the ordered or free sodium signal, the use of only a small phase cycle, and the independence of residual quadrupolar couplings.

15:00         3253.     ²³Na DQF Signal Induced by Paramagnetic Shift Reagents: Dependence on the Pseudo-Contact Shift

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Peng Rong¹, Gil Navon², Alexej Jerschow¹

¹New York University, New York , New York, USA; ²Tel Aviv University, Tel Aviv, Israel

23Na NMR/MRI in combination with paramagnetic shift agents is often used to separate the intra- from the extracellular sodium components. In addition to shifts, we recently reported relaxation effects which lead to the appearance of double-quantum coherences in isotropic phases and without slow motion. Here we show that these effects correlate with the pseudo-contact shift induced by the agents by examining the effects of the LnDOTP series.

13:30         3254.     Sodium MRI Using a Density Adapted 3D Radial Acquisition

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Armin Michael Nagel¹, Frederik Bernd Laun¹, Marc-André Weber¹, Lothar Rudi Schad

¹German Cancer Research Center, Heidelberg, Germany

A density adapted 3D Radial sampling scheme (DA-3D-RAD) was implemented. The readout gradients of the DA-3D-RAD are switched constantly up to a k-space radius k₀. Beyond this radius the gradient’s amplitude is reduced such that the sampling density in all spherical shells is kept constant. The benefits for sodium MRI compared to conventional 3D Radial sampling are demonstrated. In vivo sodium brain and phantom imaging was performed. This technique leads to a higher SNR compared to conventional radial sequences and improved resolution.

14:00         3255.     Sodium Imaging on a Whole-Body 7T Scanner: SNR and Resolution Benefits

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Yongxian QIAN¹, Yik-Kiong Hue¹, Tiejun Zhao², Tamir S. Ibrahim¹, Fernando E. Boada¹

¹University of Pittsburgh, Pittsburgh, Pennsylvania, USA; ²Siemens Medical Solutions USA, Pittsburgh, Pennsylvania, USA

This study demonstrates sodium (23Na) images of a healthy human brain acquired on a whole-body 7T scanner. The signal-to-noise ratio (SNR) of the 7T images was increased by a factor of 3.5 in comparison with the images acquired on a 3T scanner with the same acquisition parameters. The SNR gain immediately resulted in an increase in spatial resolution of the 7T image from 3.44mm to 1.72mm.

14:30         3256.     31P Imaging of the Human Brain with Balanced SSFP  - Preliminary Results [Not Available]

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Jochen Leupold¹, Roza Umarova², Jürgen Hennig¹, Cornelius Weiller², Holger Kaube²

¹University Hospital Freiburg, Dept. of Diagnostic Radiology, Medical Physics, Freiburg, Germany; ²University Hospital Freiburg, Dept. of Neuroradiology, Freiburg, Germany

Magnetic Resonance Spectroscopy of 31P is a promising tool for the examination of several pathologies and metabolic processes. A beneficial reduction of total scan time could result from utilisation of fast pulse sequences, which can acquire spatial and spectroscopic information at the same time. We show preliminary results of imaging 31P in the brain with a balanced SSFP sequence, as this sequence has potential to be the basic signal generating sequence in several fast spatial-spectroscopic methods due to its high steady state signal.

15:00         3257.     Assessment of SNR and Detection Sensitivity of F-UTSI

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Muhammed Yildirim¹,², Jochen Keupp³, Klaas Nicolay², Rolf Lamerichs¹

¹Philips Research, Eindhoven, Netherlands; ²Eindhoven University of Technology, Eindhoven, Netherlands; ³Philips Research, Hamburg, Germany

F-uTSI (Fluorine ultrafast Tutbospectroscopic Imaging) is a Turbo Spin Echo (TSE) based method developed for imaging and detection of 19F based contrast agents by avoiding the well known chemical shift. Here, the preliminary results of performance assessment of the two basic variants of the method employing cartesian and pseudo-radial sampling of the k-space are presented. A small part of the potentially large parameter space was explored for two different perfluorocarbon compounds; perfluoroctyl bromide (PFOB) and perfluoro crown teher (PFCE), by altering the field the field of view and TR and the corresponding detection limits are investigated.

Measurement of Perfusion & Permeability Using Contrast Agents

14:00         3258.     Sampling the Arterial Input Function in T1 Weighted Dynamic Contrast Enhanced Perfusion

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Adam Espe Hansen¹,², Henrik Bodil Wiberg Larsson¹

¹Glostrup Hospital, University of Copenhagen, Denmark

When using dynamic contrast enhanced (DCE) MRI to assess cerebral blood flow (CBF), correct determination of the arterial input function (AIF) is critical to CBF quantification. With T1-weighted DCE-MRI, we demonstrate the result of the partial volume effect (PVE) on CBF quantification in vivo. The larger vasculature can easily be identified and a PVE on the AIF can be introduced by displacing the AIF from the vessel centre. We further propose and test a method we denote venous normalization to compensate for PVE. This method might in particular be utilized to correct local arterial input functions.

14:30         3259.     Correcting Susceptibility Artifacts in Arterial Input Function (AIF) for Dynamic Contrast Enhancement Magnetic Resonance Imaging (DCE-MRI) at 3T

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Poe-Jou Chen¹, Wei-Ting Zhang², Rakesh K. Jain³, T T. Batchelor³, A Gregory Sorensen²

¹Massachusetts Institute of Technology, Cambridge, Massachusetts, USA; ²Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA; ³Massachusetts General Hospital, Charlestown, Massachusetts, USA

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a non-invasive imaging technique that has the ability to study tumor vascular functions. It has been widely used for a range of clinical oncologic applications including cancer detection, grading, and evaluation of therapeutic response. Unfortunately, in high field MRI (3T), the image signal is prone to susceptibility effects due to the increased relaxivity of contrast agent. In this abstract, we propose a novel method that could fully compensate the susceptibility effect and restore the full range of plasma concentration dynamic curve. The results demonstrated that, despite severe T2* effects embedded in the DCE-MRI data, the technique is able to reconstruct the plasma concentration time course and provide us a more accurate vascular input function

15:00         3260.     A Blood Circulatory Model to Estimate the Arterial Input Function in MR Brain Perfusion Studies

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Hassan Bagher-Ebadian¹,², Kourosh Jafari-Khouzani¹, Hamid Soltanian-Zadeh¹,³, James R. Ewing¹,⁴

¹Henry Ford Hospital, Detroit, Michigan, USA; ²Amir-Kabir University of Technology, Tehran, Iran; ³University of Tehran, Tehran, Iran; ⁴Oakland University, Rochester, Michigan, USA

A mathematical model of Contrast Agent(CA) concentration in the circulatory system as a function of time is of interest since it may allow the description of the AIF based on the Intravenous (IV) injection function  In this study, as a building block, the concentration-time profile in the circulatory system for each compartment was modeled by simple physical and pharmacokinetic assumptions using the Fick equation and Kety’s model. A complete model of the CA concentration as a function of time in the circulatory system was then constructed by combining those building blocks using typical flow and volume parameters for the various compartments. Using a model of the IV bolus injection, its results were compared to MR perfusion (T2*) signal, indicate that this model is a good candidate to be used to define a cost function for detection of the AIF in MR brain perfusion studies.

15:30         3261.     The Use of Phase to Measure the Arterial Input Function for Quantitative T1-Weighted DCE-MRI in Human Brain Tumors

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Claire Foottit¹, Greg O. Cron², Matthew Hogan², Thanh Nguyen², Ian Cameron,¹²

¹Carleton University, Ottawa, Canada; ²Ottawa Health Research Institute, Ottawa, Canada

When measuring perfusion quantitatively in tumors with dynamic contrast-enhanced T1-weighted MRI, it can be challenging to measure the arterial input function (AIF) in large vessels.  Blood flow and saturation effects can lead to incorrect conversion of signal magnitude to contrast agent concentration.  The signal phase, however, is largely immune to such effects, potentially providing improved AIF measurement with no added imaging time or pulse sequence modification.  Here, we used this technique to measure quantitative perfusion (Ktrans) in human brain tumors.

14:00         3262.     Utilization of Principal Component Analysis for Improved Perfusion Measurements in Highly Undersampled Radial DCE-MRI

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Junyu Guo¹, Mark A. Rosen¹, Hee Kwon Song¹

¹University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA

We investigate the feasibility and accuracy of principal component analysis (PCA) for radial DCE-MRI. It is shown that with judicious selection of principal components, PCA can effectively remove image streaking and reduce noise in a highly undersampled radial DCE-MRI data set, permitting accurate, pixel-wise measurement of the perfusion parameters.

14:30         3263.     Assessment of Image Reconstruction Methods for Subsampled DCE-MRI

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Florian Knoll¹, Franz Ebner², Stephen Keeling³, Rudolf Stollberger¹

¹TU Graz, Graz, Austria; ²Medical University Graz, Graz, Austria; ³University of Graz, Graz, Austria

Undersampled imaging techniques, in combination with advanced image reconstruction methods like HYPR or parallel imaging, have the potential to deliver high resolution DCE-MRI data sets in spatial and temporal domain, which can be used for the identification of pharmacokinetic parameters. It is, however, not clear to which extent these techniques change the time course of contrast enhancement, in particular for the arterial input function. The performance of four state of the art reconstruction methods is evaluated in this work. It is shown that the estimation of pharmacokinetic parameters can be improved significantly using these undersampled imaging techniques.

15:00         3264.     Accelerating Dynamic MRI with Efficient Multiple Acquisitions by SPEED Using Shared Information

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Zheng Chang¹, Jim Ji², Qing-San Xiang³, Fang-Fang Yin¹

¹Duke University, Durham, USA; ²Texas A&M University, College Station, Texas, USA; ³University of British Columbia, Vancouver, Canada

The efficient multiple acquisition method using Skipped Phase Encoding and Edge Deghosting (SPEED) has been successfully demonstrated in water-fat imaging with double acquisitions. In this work, it is further developed to accelerate dynamic MRI.  In dynamic MRI, multiple acquisitions of different frames are spatially correlated, and thus share similar spatial information.  By taking advantage of the shared information, dynamic MRI is accelerated by SPEED with factors greater than that achievable with a single acquisition.  In this work, a dynamic contrast enhanced mice tumor study is accelerated by a factor of 2, with results comparable to the images without acceleration.

15:30         3265.     Rapid Steady State T₁ Method for Cerebral Blood Volume Fraction Mapping Using SINEREM as Contrast Agent and a Three Dimensional Projection Reconstruction Acquisition Mode

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Adriana Teodora Perles-Barbacaru¹, Laurent Lamalle¹, Emmanuel Barbier¹, Christoph Segebarth¹, Hana Lahrech¹

¹UMR-S 836 INSERM-UJF-CEA Functional & Metabolic Neuroimaging, La Tronche Cedex, France

The USPIO SINEREM is used for cerebral blood volume fraction (CBVf) mapping with the Rapid Steady State T₁ (RSST₁) method. A steady state signal for at least one hour is obtained in rats after an intravenous injection of 0.2 mmol/kg SINEREM and was exploited for CBVf mapping in healthy and RG2 glioma bearing rats with the RSST₁ method in a 3D projection reconstruction acquisition mode enabling short echo time and with a susceptibility based steady state method for comparison. In opposite to results reported for the C6 tumor model, SINEREM seems to leak from the microvasculature in the RG2 tumor model.

DTI of the Damaged Brain

14:00         3266.     Serial Changes in Corpus Callosum Diffusion Tensor Imaging (DTI) Metrics in Moderate Traumatic Brain Injury (TBI) and Its Correlation with Neuro-Cognitive Functions

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Mazhar Husain¹, Raj Kumar¹, Rakesh K. Gupta², Khader M. Hasan³, Mohammad Haris², Atul Agarwal¹, Ponnada A. Narayana³

¹Chhatrapati Shahuji Maharaj Medical University, Lucknow, India; ²Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India; ³University of Texas Medical School at Houston, Houston, USA

Serial DTI within 2 weeks and at 6 months after TBI was performed on 38 patients with TBI [frontal (n=12), temporal (n=6), fronto-temporal (n=9) and multifocal (n=11)]. Neuropsychological tests (NPT) were performed at follow-up study and 30 age/sex matched controls. DTI was also performed in controls. The fractional anisotropy (FA) and mean diffusivity (MD) were quantified from different region of the corpus callosum (CC) in patients and controls. Decreased FA in callosal regions on follow-up study compared to controls was observed in different groups. We conclude that widespread primary abnormalities in acute stage and secondary damage after 6 months in the CC can be demonstrated on DTI. These DTI abnormalities significantly correlate with some of the NPT.

14:30         3267.     Cerebral Diffusion Tensor Imaging (DTI) and in Vivo Proton MR Spectroscopy (PMRS) in Patients with Fulminant Hepatic Failure (FHF)

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Rakesh K. Gupta¹, Sona Saksena¹, Vijan Rai¹, Vivek Anand Saraswat¹, Ram KS Rathore², Ankur Purwar², Manoj Kumar¹, M A. Thomas³

¹Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India; ²Indian Institute of Technology, Kanpur, India; ³David Geffen School of Medicine at UCLA, Los Angeles, USA

In vivo PMRS and DTI data were acquired from FHF patients (n=10) and controls (n=10). Five of the 10 patients, had a repeat imaging after three weeks. N-acetylaspartate, choline (Cho), glutamine (Gln), glutamine/glutamate (Glx), and myoinositol ratios were calculated with respect to creatine (Cr). Fractional anisotropy (FA) and mean diffusivity (MD) were quantified on different white and gray matter regions. Patients exhibited significantly increased Gln/Cr and Glx/Cr ratios compared to controls. Significantly decreased Cho/Cr was observed in deceased patients compared to controls. In patients, significantly decreased MD and FA values were observed in different brain regions compared to controls. In follow-up study, MD and FA values showed an insignificant increase.

15:00         3268.     Longitudinal Diffusion Tensor MR Imaging Study of Radiation Induced White Matter Damage in a Rat Model

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Silun Wang¹, Chung Nga Tam¹, Ed X Wu¹, Ho-Fai Lau¹, Deqiang Qiu¹, Lucullus H.T. Leung², Pek-Lan Khong¹

¹The University of Hong Kong, Hong Kong, Hong Kong; ²Princess Margaret Hospital, Hong Kong, Hong Kong

We evaluate the longitudinal changes in DTI indices and its histological correlates in a radiation induced white matter (WM) injury rat model.

The results show that radiation induced WM injury is reflected by significant reduction in FA and ¦Ë// as early as 4 weeks after injury, prior to T2WI signal changes. These changes correlate with astrocytic hypertrophy, suggesting that the relative abundance of astrocytes influence ¦Ë// in the early changes of radiation induced WM injury, and this occurs before necrosis, axonal loss and demyelination.  Therefore, FA and ¦Ë// may be biomarkers for early detection of radiation induced WM injury.

15:30         3269.     Alteration in DTI Metrics and Volume of the Mamillary Body in Patients with Hepatic Encephalopathy Secondary to Non-Alcoholic Cirrhosis

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Rakesh K. Gupta¹, Vivek A. Saraswat¹, Pooja Upreti¹, Rajendra Singh¹, Jitesh K. Singh², Richa Trivedi¹, Sunil Kumar¹, Ram KS Rathore²

¹Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India; ²Indian Institute of Technology, Kanpur, India

Diffusion tensor imaging (DTI) was performed in 28 patients with end stage chronic liver disease and 25 age/sex matched controls. Mamillary body volume and DTI metrics in mamillary body were quantified by using in-house JAVA based software. Significantly decreased fractional anisotropy (FA) and linear anisotropy (CL) with increased spherical isotropy (CS) and mean diffusivity (MD) values were observed in patients compared to controls. No change in volume of mamillary body was observed between patients and controls. Absence of the changes in the volume of the mamillary bodies compared to controls suggests that DTI is more sensitive for the early detection of changes due to thiamine deficiency in these patients.

Diffusion Modelling

14:00         3270.     Diffusion Tensor Imaging in Glioblastoma Multiforme and Brain Metastases: The Role of P, Q, L and FA [Not Available]

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Chris Steward¹,², Wayland Wang¹, Patricia Desmond¹,²

¹University of Melbourne, Melbourne, Australia; ²Royal Melbourne Hospital, Melbourne, Australia

Micro-invasive tumour cells, which are not detected on conventional imaging, contribute to poor prognoses for patients diagnosed with glioblastoma multiforme (GBM; WHO grade IV). Diffusion tensor imaging (DTI) shows promise in being able to detect this infiltration. This study aims to detect a difference in diffusion properties between GBM (infiltrative) and brain metastases (non-infiltrative).  In particular, to compare the diffusion tensor metrics p, q, L, and FA from tumoural and peritumoural regions of glioblastoma multiforme and metastatic brain tumours 2/ To determine whether these parameters can be correlated with the type of tumour and the extent of infiltration into surrounding white matter 3/ To determine whether these parameters, and more broadly DTI, has a significant clinical meaning, and thus whether it should be included in imaging protocols for suspected brain tumour and for treatment planning.

14:30         3271.     About "Axial" and "Radial" Diffusivities

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Claudia Angela Michela Wheeler-Kingshott¹, Mara Cercignani¹,²

¹Institute of Neurology, UCL, London, UK; ²Fondazione Santa Lucia, Rome, Italy

DTI allows the quantitative assessment of diffusion anisotropy in tissues. It is well known that the DT can be diagonalised, determining three eigenvectors and their eigenvalues.  We have questioned the rationale that underpins the relationship between axial and radial diffusivities and specific biophysical substrates, based on the already established knowledge of the uncertainty of the eigenvectors/values measures. Using two healthy-controls and two people-with-MS we have demonstrated what kind of serious interpretation errors can arise when comparing one or more eigenvalues of the DT across datasets. Our results are strongly supporting the not-yet-recognised need for including the eigenvectors when comparing eigenvalues.

15:00         3272.     Quantitative Relations of Axial and Radial Diffusivities to Anisotropy Indices in Diffusion Tensor Imaging

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Ling-chih Lin¹, Jianhui Zhong¹

¹University of Rochester, Rochester, New York, USA

Sensitivities of radial and axial diffusivities with respect to other diffusion anisotropy indices (DAIs) were evaluated numerically. Monte Carlo Simulation was performed to evaluate the effect of the signal to noise ratio (SNR) to their accuracy. Correlations between the axial and radial diffusivities and other DAIs were examined to facilitate the optimal selection of diffusion anisotropy measurement parameters.

15:30         3273.     Three Novel Methods for Studying Complicated Diffusion Behavior Using Simple Capillary Structures

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Nathan Yanasak¹, Qun Zhao², Tom C.-C. Hu¹, Jerry Allison¹

¹Medical College of Georgia, Augusta, USA; ²University of Georgia, Athens, USA

Although DTI has shown great clinical potential for studying a variety of neurological conditions, procedures and equipment for quality assurance of clinical data are still in development.  In particular, noise can bias anisotropy measurements, yet phantom designs are generally limited to simple anisotropic structures less characteristic of tissue.  This study introduces three new techniques to assist in the characterization of data quality for complicated tissue-like structures.  Images acting as input are acquired using a phantom with capillary structures.  In this manner, data quality from images of complex structures can be inferred from a QA phantom.

14:00         3274.     Constrained Single Step Diffusion Tensor Reconstruction Using Cholesky Decomposition

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Murat Aksoy¹, Roland Bammer¹

¹Stanford University, Stanford, California , USA

In DTI, the diffusion model requires the tensor to be positive definite. Several methods have been proposed to ensure positive definiteness, such as replacing negative eigenvalues or constraining tensors to be positive definite using matrix decomposition. In this study, we propose a single step non-linear tensor estimation scheme that utilizes Cholesky decomposition to guarantee the positive definiteness of the reconstructed diffusion tensors. The presented algorithm estimates the diffusion tensor directly from the unity of all k-space data in a non-linear fashion and it is especially effective in correcting gross patient motion in the case of multi-shot DTI scans.

14:30         3275.     Using Fractional Anisotropy Neighbourhood Information in a Bayesian Based Regularisation Technique for DTI

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Marta Morgado Correia¹, Tim Hosey¹, Sally G. Harding¹, Thomas Adrian Carpenter¹, Guy B. Williams¹

¹University of Cambridge, Cambridge, UK

A new regularisation method for DT-MRI, which is capable of improving the confidence in the FA maps obtained from diffusion weighted MRI datasets, is introduced. The idea behind this prior is that the variation of FA along a fibre tract should be smooth, and therefore if there is a tract connecting two neighbour voxels, the FA variation between these two voxels should be small. The regularisation is applied to the priors of a MCMC model rather than the data itself, meaning that the fit is biased towards spatially consistent solutions but this only when supported by the data.

15:00         3276.     Modelling Diffusion-Weighted Steady-State Free Precession in Terms of the Reciprocal Spatial Wave Vector and Non-Gaussian Diffusion Probability Density Functions

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Jennifer Andrea McNab¹, Karla L. Miller¹

¹University of Oxford, Oxford, UK

Diffusion-weighted steady-state free precession (DW-SSFP) accumulates signal from multiple echoes over several TRs yielding a strong sensitivity to diffusion with short gradient durations and imaging times. DW-SSFP is thus of great interest as a potential method for high angular and spatial resolution diffusion imaging. The DW-SSFP signal is well characterized for isotropic, Gaussian diffusion, however, it is unclear how the multi-echo signal propagates for inhomogenous media. In this study, the DW-SSFP signal equation is presented for the first time in terms of the reciprocal spatial wave vector (<B>q</B>) and an arbitrary diffusion probability density function pdf (P(r, _δ)).

15:30         3277.     Toroid-Based Characterization of Cardiac DT-MRI

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Choukri Mekkaoui¹, Marcel P. Jackowski², Albert J. Sinusas¹

¹Yale University School of Medicine, New Haven, USA; ²Institute of Mathematics and Statistics, São Paulo, Brazil

The aim of the present study is to introduce a novel toroid-based representation of diffusion tensor fields to improve myofiber visualization and macrostructure analysis. A new diffusivity index, the toroidal volume (TV), and a new coefficient of anisotropy, the toroidal volume ratio (TVR), are defined. Toroidal glyph renderings from a normal canine heart were compared to ellipsoidal and superquadric glyph fields. TV and {1-TVR} maps were calculated for a DT-MRI dataset of an infarcted canine heart and compared to contemporary indices. Results demonstrate that the proposed methodology improves diffusion tensor visualization and may complement existing diffusion indices.

MRI & MRS of Cerebral Ischemia

13:30         3278.     Susceptibility-Weighted Imaging in Hyperacute Cerebral Ischemia

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Masahiro Ida¹, Kennichi Motoyoshi¹, Hiroyuki Fukuyama¹, Hisashi Yoshizawa¹, Naoya Yorozu¹, Keiko Hino¹

¹Tokyo Metroplolitan Ebara Hospital, Oota-ku, Japan

Increased vessel contrast (IVC) suggests a relative increase of intravenous paramagnetic deoxyHb and a relative reduction of oxyHb due to the impaired oxygenation (misery perfusion state). SWI can detect not only an area of perfusion impairment but also occluded artery. SWI provides important adjunct information for HIS. IVC is a useful finding to assess acute misery perfusion state without contrast media and a reliable indicator for determining whether a patient should undergo Gd-perfusion study.

14:00         3279.     Feasibility of Longitudinal Study Using Arterial Spin-Labeling Perfusion MRI in Pediatric Arterial Ischemic Stroke

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Juan Chen¹,², Daniel J. Licht³, Yong Fan¹, Sabrina E. Smith³, Shannon C. Agner³, Stefanie Mason³, Robert A. Zimmerman³, Rebecca N. Ichord³, Jiongjiong Wang¹

¹University of Pennsylvania, Philadelphia, Pennsylvania, USA; ²Beijing Hospital, Beijing, People's Republic of China; ³the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA

This is a longitudinal study of cerebral perfusion and lesion volume changes in three pediatric patients with acute stroke. The aim of the study was to demonstrate feasibility of pulsed arterial spin-label (PASL) perfusion MRI to follow perfusion deficits and their relation with changes in lesion volume over time. Ischemic lesions showed a trend of decreasing volume over time accompanied by decreasing perfusion within the shrinking lesion. Voxel-based scatterplot analysis of the region of diffusion restriction indicate that tissue within the lesion has relatively higher perfusion and may represent viable and potentially salvageable tissue.

14:30         3280.     Altered Regional CO2 Vasoreactivity in Patients with Ischemic Stroke Using CASL MRI

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Peng Zhao¹, David Alsop², Magdy Selim³, Amir Abduljalil⁴, Peter Novak⁵, Lewis Lipsitz¹, Kun Hu¹, Sarah LaRose¹, Vera Novak¹

¹Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA; ²Radiology, Beth Israel Deaconess Medical Center,, Boston, Massachusetts, USA; ³Neurology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA

This study investigated the regional differences in CO2 vasoreactivity (CO2VR) after stroke and their relationship to clinical outcomes. 27 subjects with chronic large vessel infarcts in the middle cerebral artery (MCA) territory were compared with 43 controls by using continuous arterial spin labeling (CASL) perfusion MRI. Impairment of CO2VR after stroke was observed which extended into additional brain regions and vascular territories not within the ischemic region.

15:00         3281.     Quantitative Assessment of Brain Mass Effect Using Mid-Brain Surface in Stroke Patients

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Yasheng Chen¹, Chung-Yi Yang², Cheng-Hong Toh¹, Hongyu An¹, Allyson Zazulia³, Thomas Vedeen³, Michael Diringer³, William Powers¹, Weili Lin¹

¹The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA; ²National Taiwan University Hospital, Taiwan; ³Washington University in St. Louis, St. Louis, Missouri, USA

The current approach for quantitatively measuring brain mass effect employs manual measurements of the 2D displacement between the altered brain midline and the putative normal midline in specific anatomical locations including the pineal body, septum pellucidum, and third ventricle.  One major limitation associated with this approach is the inability to assess the true 3D extent of brain mass effect.  An automated approach reconstructing the mid-brain surface is developed, allowing a direct assessment of mass effects through measuring the volume enclosed by the deformed and the estimated of un-deformed brain mid-surface.

13:30         3282.     White Matter Integrity But Not BOLD Response Predicts Upper Limb Motor Function in Patients After Stroke

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mingguo qiu¹, Justin Rajendra², Warren Darling³, Robert Morecraft⁴, Chunchun Ni², Andrew J. Butler²

¹Southwest hospital of Third military medical university, chongqing, People's Republic of China; ²Emory University, School of Medicine, Atlanta, Georgia, USA; ³The University of Iowa, Iowa City, Iowa, USA; ⁴Univ

The aim was to establish the relationship between upper-extremity motor functional outcomes with the asymmetry of fractional anisotropy (FA) from DTI and with the laterality index (LI) derived from functional MRI. Seventeen patients after stroke were enrolled and measured the motor function by Wolf Motor Function Test (WMFT) and Fugl-Meyer (FM) assessment. The data showed a significant relationship between FA asymmetry of PLIC with FM and WMFT asymmetry, white matter integrity can strongly predict current motor function.  However, LI can’t predict the current clinical outcomes; no relationship was found between the LI with the FA asymmetry and clinical motor outcomes.

14:00         3283.     Assessing the Evolution of Sodium MRI with Time After Onset in Human Stroke

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Robert Wayne Stobbe¹, Muhammad Shazam Hussain², Yusuf A. Bhagat², Ken S. Butcher¹, Derek J. Emery¹, N Rizvi¹, Perkash Maheshwari¹, Ashfaq Schuaib¹, Christian Beaulieu¹

¹University of Alberta, Edmonton, Canada; ²University of Alberta, Edmonton , Canada

Sodium MRI signal intensity within the ischemic lesion is shown to evolve over time after symptom onset in human acute stroke. Given significant early changes it may be possible to estimate time of onset in patients when this important factor is unknown, and possibly increase options for treatment.

14:30         3284.     Elevated Choline/Creatine Ratio in Central Nervous System Arterial Infarction: Frequency, Timing, Extent and the Effect of Echo Time

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Metin Bora Vardar¹, Gur Akansel,¹², Nagihan Inan¹,¹, Hasan Tahsin Sarisoy¹,¹, Arzu Serpil Arslan¹,¹, Ercument Ciftci¹,¹, Ali Demirci¹,¹

¹; ²Kocaeli University School of Medicine, Kocaeli, Turkey

Although the MRI diagnosis of cerebral infarction is usually straightforward with the use of diffusion-weighted imaging, infarcts first seen in the late subacute stage remain a challenge to differentiate from neoplasm. Since cytotoxic edema subsides in the late subacute period, abnormalities of apparent diffusion coefficient due to restricted water diffusion are of limited help. Hemorrhagic transformation and abnormal contrast enhancement due to blood brain barrier breakdown may further complicate the picture.

A common clinical indication for proton MRS is the differentiation of neoplastic from non-neoplastic central nervous system lesions. MRS is frequently performed to differentiate subacute infarcts from neoplasm. However, elevated choline content that may be encountered in subacute infarcts may impede the contribution of MRS in this differentiation.

In this study, we evaluated choline/Creatine ratios in cases of acute, subacute and chronic central nervous system infarction to detect the frequency, timing and the extent of the elevation in choline/Creatine ratio. Our aim was to determine if the MRS pattern in subacute infarction was sufficiently different from that which characterizes a neoplasm.

15:00         3285.     fMRI of Rehabilitation in Chronic Stroke Using MR-Compatible Robots

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Dionyssios Mintzopoulos¹,², Loukas G. Astrakas¹, Walter J. Koroshetz¹, Michael A. Moskowitz¹, Bruce R. Rosen¹, A Aria Tzika¹

¹Massachusetts General Hospital, Boston, Massachusetts, USA

Using a hand motor task, we investigated brain activation after chronic stroke by combining fMRI at 3T with a novel MR-compatible hand-induced, robotic device (MR_CHIROD). Patients trained at home using a gel ball; serial neuroimaging was performed before, during, upon completion of training, and after a non-training period, to assess permanence of effects. Training significantly increased the number of activated voxels in the cortex as a function of effort level, suggesting functional cortical plasticity in chronic stroke. The result¢s persistence indicates permanence of rehabilitation, which is remarkable given that training is generally effective during a narrow window after stroke.

13:30         3286.     MRI Metrics Detected Axonal Outgrowth and Plasticity in Rat Brain After Embolic Stroke [Not Available]

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Guangliang Ding¹, Quan Jiang¹, Lian Li¹, Li Zhang¹, Zhanggang Zhang¹, Karyn A. Ledbetter¹,², Swayamprava Panda¹, Siamak P.N. Davarani¹,³, James R. Ewing¹, Michael Chopp¹,⁴

¹Henry Ford Health System, Detroit, USA; ²Michigan State University, East Lansing, USA; ³University of Michigan, Ann Arbor, USA; ⁴Oakland University, Rochester, USA

Both angiogenesis and axonal outgrowth were detected as early as 1 week after stroke in sildenafil treated rats. Angiogenesis and axonal plasticity were co-localized with each other, measured histologically at 6 weeks and dynamically in vivo by MRI up to 6 weeks after stroke. This indicates that sildenafil treatment of stroke may simultaneously promote angiogenesis and axonal plasticity after embolism in rats. Local CBF in the co-localized area was increased after angiogenesis. Both elevated CBF and re-organized white matter in ischemic areas may contribute to recovery of neuronal function after stroke in rats.

14:00         3287.     Noninvasive Detection of White Matter Reorganization Enhanced by Erythropoietin Treatment in a Rat Model of Focal Ischemia Using MRI

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Lian Li¹, Quan Jiang¹, Guangliang Ding¹, Li Zhang¹, Zhenggang Zhang¹, James R. Ewing¹, Michael Chopp¹,²

¹Henry Ford Health System, Detroit, Michigan, USA; ²Oakland University, Rochester, Michigan, USA

The objective of the present study was to noninvasively identify and monitor the progress of white matter reorganization within 6 weeks after the onset of stroke and correlate this structural change with improved neurological function using MRI. Our data in rats indicate that FA is a sensitive measure of white matter changes after stroke and provides an important noninvasive means for real-time evaluation of treatment efficacy and functional outcome. Treatment with EPO significantly enhances white matter reorganization, which correlates with local restoration of CBF and recovery of neurological function

14:30         3288.     Increased Connectivity of the Contralesional Sensorimotor Cortex at a Chronic Stage After Stroke as Studied by Manganese-Enhanced MRI in Rats

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Maurits Pieter Adriaan van Meer¹,², Wim M. Otte¹, Kajo van der Marel¹, J. W. Berkelbach van der Sprenkel¹, Rick M. Dijkhuizen¹

¹University Medical Center Utrecht, Utrecht, Netherlands

Manganese-enhanced MRI was applied after injection of MnCl2 in the contralesional primary sensorimotor cortex of rats at 10 weeks after unilateral stroke. Subsequent ROI analysis of the time-course of manganese-induced R1 increases revealed increased tracer uptake and distribution in contralesional subcortical ROIs and ipsilesional cortical ROIs as compared to controls. Our data support the concept of structural remodeling of the contralesional cortex and increased connectivity with other sensorimotor network areas, which may significantly contribute to post-stroke functional recovery.

15:00         3289.     Magnetic Resonance Imaging of Delayed Administration of Manganese After Transient Focal Cerebral Ischemia

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Kevin C. Chan¹,², Victor K. Hung¹, Matthew M. Cheung¹, Ke Xia Cai¹, Dave K. Cheung¹, Chi-tat Chiu¹, Po-mak Chan¹, Xiao-guang Zhao¹, Sookja K. Chung¹, Ed Xuekui Wu¹

¹The University of Hong Kong, Pokfulam, Hong Kong

This study aims to employ in vivo magnetic resonance imaging to understand longitudinally the effect of systemic MnCl2 administration on delayed secondary changes after transient middle cerebral artery occlusion (MCAO).  Results showed a significant increase in T1 signal intensities in the perilesional rim compared to the ischemic core in dorsolateral striatum 24 hours after Mn2+ injection, whereas colocalization was found between manganese-enhanced MRI pattern and immunostaining for GFAP, MnSOD and GS, likely due to their Mn-dependent upregulation against oxidative stress and glutamate excitotoxicity. Total ipsilateral infarcted volumes in the posterior parts of the brain had also significantly reduced after Mn2+ injection, illustrating the potential neuroprotective effects of manganese upon delayed postischemic administration.

13:30         3290.     Delayed T2 Changes Following Cerebral Ischaemia and Cell Transplantation with Ferumoxide-Labelled Neural Stem Cells

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Rachael Dobson¹,², Patrizia Ferretti¹, Mark F. Lythgoe¹

¹University College London, London, UK

Transplantation of stem cells following cerebral ischaemia has been shown to improve functional outcome. MRI contrast agents have been used to track the migration of transplanted cells towards lesions. The protamine sulphate-ferumoxide complex – FePro –enhances cell labelling. In this study, migration of neural stem cells, labelled with FePro, was monitored using MRI in a model of cerebral ischaemia. Little migration was observed. Hypointense regions on T2-weighted images developed within lesions, and iron was detected histologically, in cell treatment and control groups. These results highlight issues for cell tracking studies using MRI contrast agents in animal models of disease.

14:00         3291.     MRI Evaluation of the Effect of a COX-2 Inhibitor on BBB Permeability in a Rat Stroke Model

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Saeid Taheri¹, Eduardo Candellario-Jalil¹, Eduardo Estrada¹, Gary Rosenberg¹, Rohit Sood¹

¹University of New Mexico, Albuquerque, New Mexico, USA

Recent research has demonstrated an increase in expression of cyclooxygenase (COX-2) mRNA within neurons and vascular cells and it has been postulated that COX-2 plays an important role in secondary events that amplify brain damage post-ischemia. There is additional evidence that COX-2 is involved in the increase in BBB permeability. The purpose of this study was to use MRI based BBB permeability estimation technique to evaluate the effects of nimesulide, a non-steroidal anti inflammatory drug on BBB permeability in a rat model with focal cerebral ischemia at 48h post MCAO. Initial results suggest that nimesulide is effective in reducing BBB damage 48h post ischemia and would be potential candidate for therapeutically reducing late phase brain damage post ischemic stroke.

14:30         3292.     in vivo ¹H/¹³C MRSI of Changes in Neurotransmitter Metabolism in Rats Recovering from Stroke

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Pieter van Eijsden¹, Jet P. van der Zijden², Robin A. de Graaf³, Rick M. Dijkhuizen²

¹University Medical Center, Utrecht, Netherlands; ²University Medical Center Utrecht, Netherlands; ³Yale University, New Haven, USA

Post-stroke functional recovery has been associated with brain plasticity in the lesion borderzone, but its metabolic basis is unknown. To characterize alterations in oxidative glycolysis and neurotransmitter metabolism, we applied in vivo dynamic ¹H/¹³C MR spectroscopic imaging after infusion of ¹³C-labeled glucose in rats after transient stroke. Semi-acutely, reductions in NAA levels and Glu turnover implied severe neuronal dysfunction in the lesion borderzone. At 3 weeks post-stroke, NAA levels and Glu turnover had normalized, suggestive of neuronal recovery. Our findings show that early metabolic impairment in the morphologically intact lesion borderzone recovers over time, contributing to post-stroke functional improvement.

15:00         3293.     Magnetic Resonance Spectroscopy and Imaging at 9.4T in P4 Rat Pup Brain Following Cerebral Hypoxia-Ischemia

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Yohan van de Looij¹,², Alexandra Chatagner², Nicolas Kunz¹, Petra S. Hüppi², Stéphane V. Sizonenko², Rolf Gruetter¹,³

¹Laboratory for Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; ²Division of Child Growth & Development, Department of Pediatrics, University of Geneva, Geneva, Switzerland

To define the nature of diffuse injuries of the very preterm infant, we use the model of neonatal hypoxic-ischemic injury in the 3-day old (P3) rat pup and we investigate acute and long term brain alterations using high-field MRI and MRS. At P4, the ispilateral cortex indicated significant modifications for several metabolites reflecting an energetic and functional slowing-down of the injured cortex. At P11 no significant differences between both cortices were found, ascribed to a low number of animals and possibly to intervening partial tissue repair. Relation between metabolic changes and severity of the injury requires further investigations.

13:30         3294.     In Vivo Early MRI and MRS at 9.4T of Combined Hypoxia-Hypotension and Traumatic Brain Injury in the Rat

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Bich-Thuy Doan¹,², Fanny Noury³, Thomas Geeraerts⁴, Arnaud Friggeri⁵, Philippe Meric¹, Sandra Meme³, Bernard Vigue⁴, Jean-Claude BeloeilL³

¹CNRS, Gif sur Yvette, France; ²Orléans, France; ³CNRS, Orléans, France; ⁴AP-HP, University of Paris Sud, Kremlin Bicetre, France; ⁵AP-HP, France

Following traumatic brain injury (TBI), hypoxia and hypotension are frequent and damaging secondary insults.

The aim of this work is to characterize the traumatic injury by MRI (T2, diffusion tensor, angiography) and MRS experiments in vivo on rat brain. The final aim is to understand the role of secondary insults like hypoxia and hypotension (HH) in the development of post-traumatic brain oedema.

Using an animal model of diffuse TBI complicated by HH, we focused on post-traumatic brain oedema development using MRI combined with MRS, as well as consequences of post-traumatic perturbations on brain energy metabolism using cerebral microdialysis.

14:00         3295.     Single Voxel MR Spectroscopy with Echo Times Below 2 Ms at 16.4 T in the Rat Brain: First in vivo Results

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David Zsolt Balla¹, Sung-Tak Hong¹, Gunamony Shajan¹, Rolf Pohmann¹, Kamil Ugurbil¹,²

¹Max Planck Intitute for Biological Cybernetics, Tuebingen, Germany; ²Center for Magnetic Resonance Research, Minneapolis, USA

Single voxel MRS techniques employ at least three RF-pulses to generate an echo in the selected volume and gradients to dephase magnetization in the outer region. During the time between excitation and acquisition, relaxation effects and phase modulation by J-couplings affect the NMR signal. The STEAM sequence can be applied with very short echo times to obtain localized spectra containing fast decaying components and peaks from all detectable coupled resonances. We show in vivo spectra from the rat brain acquired at 16.4 T with localized spectroscopy using echo times below 2 ms and compare them to results from the literature.

14:30         3296.     Time Courses and Correlation of Diffusion-Weighted MR and CT Imaging in Acute MCA Ischemia with Rat Model

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Hyung Suk Seo¹, Dong Gyu Na²

¹dongguk university international hospital, goyangsi, Republic of Korea; ²Seoul National University College of Medicine, Seoul, Republic of Korea

Unlike ADC value, DWI signal in acute cerebral ischemia increases with time and correlates with CT density, which decrease with time. It means that the signal change of DWI after 3 hours is influenced by net water uptake in ischemic edema rather than by restricted water diffusion and DWI will be used as the predictor of ischemic injury severity like CT.

15:00         3297.     Brain Tissue Ischemic Transitions During Permanent Middle Cerebral Artery Occlusion (PMCAO) in Rats

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Lesley May Foley¹, T. Kevin Hitchens¹, Brent Barbe², Joyce A. Horner¹, Edwin M. Nemoto²

¹Carnegie Mellon University, Pittsburgh, Pennsylvania, USA; ²University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA

The identification of the ischemic penumbra in acute stroke is important for therapeutic intervention.  Whereas qualitative MRI perfusion and diffusion mismatch does not accurately identify the ischemic penumbra, it may be identified by quantitative measurements using ASL for perfusion and ADC with appropriate thresholds.  Using these methods, we were able to describe brain tissue ischemic transitions in the first four hours and up to three weeks after pMCAO.

13:30         3298.     Mild Hypoxic-Ischemic Brain Injury in Neonatal Rats Using Diffusion Tensor MR Imaging: A Longitudinal Study

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Silun Wang¹, Ed X Wu¹, Chung Nga Tam¹, Edward S Hui¹, Pek-Lan Khong¹

¹The University of Hong Kong, Hong Kong, Hong Kong

We evaluate the longitudinal changes (D1 to D90 post-injury) in the white matter (WM) of a mild hypoxic-ischemic (HI) rat brain injury model using DTI and correlate the findings with histology. Significantly elevated ¦Ë¡Í with no change in ¦Ë// in the ipsilateral WM was found, suggesting reduced myelination in the ipsilateral WM as a consequence of mild HI injury and this was confirmed by Luxol fast blue stain. Longitudinal changes of DTI indices on the ipsilateral WM parallel changes of normal development in the contralateral WM suggesting continual maturation processes after HI injury.

14:00         3299.     Comparison of Two Methods of Assessment of Perfusion-Diffusion Mismatch in a Rodent Model of Ischemic Stroke
[Not Available]

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Feng Chen¹, Yicheng Ni¹, Guy Marchal, Jie Yu¹, Yasohiro Suzuki, Nobuo Nagai

¹Catholic University of Leuven, Leuven, Belgium

The present study demonstrated that the PWI-ADC pattern evolves from a mismatch pattern through a match pattern to a reversed mismatch pattern after stroke onset. The PWI-ADC mismatch pattern was observed up to 72h after MCA occlusion in this animal model. There are linear correlations of volume and mismatch occurrence between e(early)PWI-i(instant)ADC and iPWI-iADC models. The PWI-ADC pattern could be defined either with ePWI or iPWI before 24h after stroke onset. The iPWI appeared more adequate compared to ePWI to define the PWI-ADC pattern at 72h.

Diffusion: Artifacts, Phantoms, QA, Reproducibility

13:30         3300.     Quality Assessment Through Analysis of REsiduals of Diffusion Image Fitting

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Alexander Leemans¹, Christopher John Evans¹,², Derek K. Jones¹

¹School of Psychology, Cardiff University, Cardiff, UK; ²GE Healthcare, Chalfont St. Giles, UK

In order to obtain reliable quantitative results, it is important to assess the quality of DTI data with respect to subject motion, distortions, signal dropouts, etc. prior to performing further analyses. In this context, we developed a comprehensive DTI quality assessment (QA) tool that provides a ‘direct feel’ and ‘global overview’ of the data in an automatic way. We show how this exploratory tool can be used to efficiently identify subject motion, signal dropouts, and image distortions, without the need to perform QA on all the individual diffusion weigthed MR images.

14:00         3301.     Analysis of Noise Corrected Diffusion Decay of Human Brain

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Elena Olariu¹, Arturo Cardenas-Blanco², Ian Cameron,¹²

¹Carleton University, Ottawa, Canada; ²Ottawa Health Research Institute, Ottawa, Canada

Several studies have shown that, there is a significant deviation of the MR signal, for both gray matter (GM) and white matter (WM), from the mono-exponential model; however, there is no clear consensus as to whether the diffusion decay has one or more exponential contributions. Our purpose was to carefully characterize the diffusion attenuation in WM and GM over an extended range of b-values, and to use a post-processing scheme to reduce the noise bias to see if a second exponential component could be observed.

14:30         3302.     Quality Assurance of MR Scanner on Diffusion Tensor Imaging [Not Available]

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Zili Chu¹,², Jonathan Chia³, Zhiyue J. Wang¹,²

¹Baylor College of Medicine, Houston, Texas, USA; ²Texas Children's Hospital, Houston, Texas, USA; ³Philips Medical Systems, Cleveland, Ohio, USA

Diffusion Tensor Imaging (DTI) is prone to artifacts associated with EPI and strong diffusion encoding gradients. Therefore, periodically assessing the performance of the scanner on the DTI sequence is essential to ensure good image quality. Here, we propose the use of a glycerin-gel spherical phantom constructed to be similar to the human brain in terms of apparent diffusion coefficient (ADC) and T2.The temperature of the phantom is controlled during the QA data acquisition. The calculated ADC, FA, image center displacement and distortion on the DTI data of the phantom can be analyzed to  serve as indicators of the scanner performance.

15:00         3303.     A Frame-Work for DTI Quantitation, Visualization & Analysis

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Ankur Purwar¹, RKS Rathore¹, RK Gupta², D Rathore¹, G Bayu¹, MK Sarma¹, Anup Singh¹, JK Singh¹, S Verma¹

¹IIT Kanpur, Kanpur, India; ²SGPGIMS Lucknow, Lucknow, India

DTI is an important tool to study brain white matter anatomy/abnormalities. The data processing and analysis in DTI is quite elaborate and so far no commercial and easily extendable/modifiable tool for the same is available. In view of the same, we present a tool frame-work focusing on DTI technology combining all of the above needs. It has 4 mutually independent modules namely DTI Processing Module, DTI Visualization Module, ROI Analysis Module and Tracking and Fiber data Visualization Module. The Tool can read various data formats from different scanners including the raw binary format. An automatic de-scalping procedure is also implemented.

13:30         3304.     Validation of Diffusion Tensor Imaging and Tractography of the Human Peripheral Nerve Using Small-Diameter Ex Vivo Phantoms

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Akira Kunimatsu¹,², Masayuki Yamaguchi², Yoshikazu Okamoto¹, Izumi Anno¹, Hirofumi Fujii², Atsushi Nozaki³, Hiroyuki Kabasawa³, Manabu Minami¹

¹Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Japan; ²Research Center for Innovative Oncology, National Cancer Center Hospital East, Kashiwa, Japan; ³GE Yokogawa Medical Systems, Hino, Japan

We aimed to develop small-diameter, flexible, ex-vivo phantoms for validation of diffusion tensor (DT) imaging and tractography of the human peripheral nerve on a clinical MR imager with standard coils. Our results suggest that DT imaging and tractography are feasible even with a 4-mm-diameter phantom on a clinical imager without any dedicated or special coil. Four or more numbers of excitations and 15 or more motion probing gradient directions may provide robust results of fractional anisotropy measurement and fiber-tracking of the human peripheral nerve.

14:00         3305.     Impact of Resolution on Tissue-Specific DTI Parameters at 3T: Roles of Partial Volume, SNR and Tissue Structure

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Xiaogeng Feng¹, Dae-Shik Kim¹, Itamar Ronen¹

¹Boston University School of Medicine, Boston, Massachusetts, USA

With the proliferation of high field MRI scanners (B0 &[ge] 3T), it is now possible to acquire DTI data of the human brain at a reasonably high spatial resolution. Increased resolution, however, has implications on the assessment of DTI parameters such as ADC and FA that are different for white matter and cortical gray matter. This work aims to evaluate the tissue-specific effects of increased resolution in carefully segmented DTI data sets and explain the interplay between SNR, partial volume effects and macroscopic characteristics (e.g. curvature effects), which is shown to be significantly different in brain gray and white matter.

14:30         3306.     Simple, Reliable and Precise Quantitative Quality Assurance of In-Vivo Brain ADC

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Nicholas G. Dowell¹,², Paul S. Tofts¹,²

¹University of Sussex, Falmer, UK; ²UCL, London, UK

Measuring diffusion with MRI is a useful and popular method of studying many pathological conditions in vivo. The apparent diffusion coefficient (ADC) is commonly used to quantify the extent of diffusion; however, there is a need for reliable quantitative quality assurance of the technique. We use decane, dodecane and tetradecane as test liquids that exhibit similar ADC values to those observed in the human brain in vivo. We demonstrate that serial measurements of ADC can be referenced to a standard temperature to avoid variation due to temperature fluctuations. The materials used here are stable, readily available and safe to handle.

15:00         3307.     Looking for the Optimal DTI Acquisition Scheme Given a Maximum Scan Time: Are More B-Values a Waste of Time?

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Marta Morgado Correia¹, Thomas Adrian Carpenter¹, Guy B. Williams¹

¹University of Cambridge, Cambridge, UK

By using simulated data, this study has shown that the use of more than 1 b-value in DTI acquisition schemes can minimize the systematic bias of ADC and FA estimates due to the Rician noise distribution, and also produce results closer to the simulates ones and less variable due to noise and fibre rotation. In addition, the use of more than 1 b-value accounts better for the great diversity of diffusivities we find in the brain. For tractography studies, however, we should use as many sampling directions as allowed by scan time limitations.

Fiber Tracking & Connectivity Mapping

13:30         3308.     In Vivo Localisation of Fibre Tracts: Optimisation of Fibre Tracking to Reduce Voxel Misclassification

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J-Donald Tournier¹,², Fernando Calamante¹,², Alan Connelly¹,²

¹Brain Research Institute, Melbourne, Australia; ²University of Melbourne, Melbourne, Australia

Diffusion tractography is increasingly being used in clinical and neuroscientific applications. However, reliable tracking requires methods to resolve crossing fibres that have yet to be optimised. Here, we investigate the effects of acquisition and reconstruction parameters on the reconstructed fibre tracts estimated using sophisticated methods, by quantifying the volume of white matter misclassified as belonging or not to the tract. We show that misclassified volume is consistently reduced by using more diffusion-weighted directions and higher spherical harmonic orders. Measures of false tract and omitted tract volume also provide a means of tailoring the acquisition and reconstruction to the application.

14:00         3309.     A New Fiber Tract Color-Encoding Scheme Based on Diffusion Tensor  Model Residuals

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Alexander Leemans¹, Derek K. Jones¹

¹School of Psychology, Cardiff University, Cardiff, UK

Due to the multi-component nature of DTI data, distinguishing between real and artifactual observations is often non-trivial. To bridge this gap between the acquired images and the understanding of the underlying WM microstructure, specialized visualization methods have been developed that display various WM properties along the fiber tracts. However, none of these visualization approaches reflects the acquired data quality (artifacts) or Goodness-of-Fit (GoF) to the model, which is crucial in interpreting analysis results. In this context, we developed a new color-encoding scheme for visualizing fiber tracts, based on the analysis of tensor model residuals, which allows the investigation of data quality and GoF.

14:30         3310.     Combination of Distance Measures for Optimal Fiber Clustering in Diffusion Tensor Imaging

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Daniel Güllmar¹,², Jana Langner¹, Jens Haueisen², Jürgen R. Reichenbach¹

¹University Hospital Jena, Jena, Germany; ²TU Ilmenau, Illmenau, Germany

From Diffusion Tensor data of the human brain one can derive beautiful fiber tracts employing deterministic algorithms in order to mimic the neuronal pathways. However it is hard to distinguish between the different tracts, although the tracts itself are easy to recognize by visual inspection. Several studies showed that one can perform clustering based on distance measures between the fiber path ways. Thus it is possible to objectively group the paths in order to distinguish between at least the major tracts. The aim of the presented study is to combine different distance measures to handle deficiencies of single distance measures.

15:00         3311.     Tracking of CE-MR-Angiography Data Using Established Approaches in DTI

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Daniel Güllmar¹,², Andreas Deistung¹, Stefan Richter¹, Jens Haueisen², Jürgen R. Reichenbach¹

¹University Hospital Jena, Jena, Germany; ²TU Ilmenau, Ilmenau, Germany

We propose a method to generate tractograms from CE-MR-Angiography data using existing tools designed to work on diffusion tensor data. The pseudo DT data are generated by converting the Hessian matrix derived from a multi-scale approach in order to obtain a highly anisotropic tensor representation along the vascular system. The results derived from a high resolution 3D MR angiographic extremity data set demonstrate that it is possible to reconstruct the vascular system with diffusion tensor fiber tracking tools. Only deterministic tracking was applied so far which leads to some extent to fragmentary reconstruction, which may be overcome by probabilistic tracking.

13:30         3312.     Local DTI Connectivity Estimation Using Bayesian Probability Theory

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Joshua S. Shimony¹, Adrian A. Epstein¹, G Larry Bretthorst¹

¹Washington University School of Medicine, St. Louis, Missouri, USA

The diffusion tensor model has been used to analyze magnetic resonance diffusion data and has been successful in both neuroscientific and clinical applications.  We propose an enhancement of this model with a local connectivity parameter that better accords with the known structure of white-matter.  In addition to providing diffusion tensor parameter estimation the calculation provides the probability that a given pixel is connected to one of its nearest neighbors.  These probabilities can be used in further calculations to determine the probability of connectivity between different brain regions.

14:00         3313.     White Matter Tract Probability Atlas Derived from Diffusion Tensor Tractography of a Large Population

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Catherine Lebel¹, Luis Concha¹, Gaolang Gong¹, Christian Beaulieu¹

¹University of Alberta, Edmonton, Canada

Brain white matter is usually crudely parcellated based on lobar location in existing human brain atlases. Recent attempts to create a more detailed

white matter atlas based on information derived from diffusion tractography have been reported, but are limited by small sample sizes. We investigated the spatial variability in standard space of thirteen white matter structures defined by tractography in a group of 254 healthy volunteers. The core of the white matter structures shows high spatial overlap amongst individuals, while the edges show high variability. Our results could provide valuable information for the interpretation of voxel-based analyses.

14:30         3314.     Improving the Efficiency of Tractography by Combining DTI with Prospective Partial-Brain Q-Ball Imaging

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Jiancheng Zhuang¹, Nicolas Lori¹, Christine Vidal¹, Hanna Damasio¹

¹University of Southern California, Los Angeles, USA

This study proposed to develop a method which combines the conventional DTI and a prospective partial-brain QBI to improve the efficiency of tractography. The non-Gaussian ADC profile detected from DTI data was used to indicate which brain region to be covered by QBI. The multiple wavevector fusion (MWF) algorithm was performed in the combination of data, and multiple FACT algorithm was applied in fiber tracking. The quality of connectivity detection in this approach is sufficiently high, and the scan time is reduced by about 65.3% when compared with a similar QBI with the whole brain coverage.

15:00         3315.     Connectivity-Based Probabilistic Parcellation of the Striatum in Human Brain by Diffusion Tensor Imaging

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mingguo qiu¹, qiyu li¹, jian wang², bing xie², shaoxiang zhang¹

¹Third military medical university, chongqing, People's Republic of China; ²southwest hospital of Third military medical university, People's Republic of China

The aim is to investigate the corticostriatal connections in human by DTI. The results showed the frontal projections were located to the head of the caudate nucleus and the superior part of the putamen, the insular projections to the lateral striatum, the projections from the parietal, temporal and occipital lobes overlapped to the posterior part and the inferior part of the striatum. M1 were connected to the posterosuperior part, SMA to the middle part and PMC to the anterior and posteroinferior striatum. The striatum have specific connections with the different cortex, connectivity-based probabilistic tractography and parcellation is valuable in the functional anatomy of human brain.

13:30         3316.     Diffusion Tensor Imaging Fiber Tracking of the Nigro-Striatal Fiber Tract in the Monkey Brain Using Whole Body 7T

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Stephane Lehericy¹, Essa Yacoub², Eric Bardinet¹, Romain Valabregue¹, Chantal Francois¹, Geoff Ghose², Noam Harel²

¹University Pierre and Marie Curie, Paris, France; ²University of Minnesota, Minneapolis, Minnesota, USA

In this work, we used 7T whole body and diffusion tensor imaging (DTI) to reconstruct the nigro-striatal fiber tract in the anesthetized macaque brain. DTI was performed using a single shot SE acquisition. The nigro-striatal fiber tract was reconstructed between the segmented substantia nigra and lenticular nucleus. The tract coursed from the medial part of the substantia nigra anteriorly toward the medial part of the globus pallidus. DTI reconstruction of the nigro-striatal fiber tract provides a marker of the nigro-striatal pathway that can be used to study basal ganglia pathology such as Parkinson’s disease.

14:00         3317.     High Resolution Probablistic Tractography in Whole, Fixed, Human Brain Using Diffusion-Weighted Steady-State Free Precession

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Jennifer A. McNab¹, Saad Jbabdi¹, Sean C.L. Deoni,¹², Gwenaelle Douaud¹, Timothy E.J. Behrens¹, Karla L. Miller¹

¹University of Oxford, Oxford, UK; ²Institute of Psychiatry, King's College, University of London, London, UK

This study presents a robust method for estimating the principal diffusion direction from multi-angle DW-SSFP data and demonstrates probabilistic tractography at sub-millimeter resolution in a whole, fixed human brain.

14:30         3318.     Atlas-Based Reference Tracts Improve Automatic White Matter Segmentation with Neighbourhood Tractography

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Susana Muñoz Maniega¹, Mark E. Bastin¹, Andrew M. McIntosh¹, Stephen M. Lawrie¹, Jonathan D. Clayden²

¹University of Edinburgh, Edinburgh, UK; ²UCL , London, UK

Neighbourhood tractography is a novel technique that aims to automatically segment the same fasciculus in different subjects by scoring the similarity between a predefined “reference tract” and a group of candidate tracts generated with different initial seed points. In the current work we present a means of improving the technique by generating the reference tract from an anatomical atlas. Using diffusion data from 50 volunteers we found that atlas-generated reference tracts improved the segmentation results in the four fasciculi examined, obtaining lower variation of FA within the group and percentages of visually plausible tracts of up to 82%.

15:00         3319.     Using BCP Index to Evaluate Coregistration Methods in Existing SPM2 [Not Available]

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Shiou-Ping Lee¹, Kao-Lun Wang¹, Chung-Ming Chen², Wen-Yih Isaac Tseng³

¹Far Eastern Memorial Hospital, Taipei, Taiwan; ²National Taiwan University Hospital, Taipei, Taiwan; ³National Taiwan University Medical College, Taipei, Taiwan

A novel indices, Bundle Curvature Profile (BCP), was proposed as the basis to quantify the similarity of four fiber bundles to distinguish geometric significant difference. In this study, we corrected diffusion tensor imaging data using four different SPM2 built-in coregistration functions, i.e., normalized mutual information (NMI), mutual-information (MI), entropy correlation coefficient (ECC) and normalized correlation coefficient (NCC). We also applied coherence index (CI) to evaluate the accuracy of fiber tractography in corpus callosum. In conclusion, the proposed BCP index is also capable in revealing the difference between four coregistration functions which is consistent with the results from CI index whereas the similarity of fiber tracking using NCC correction method is higher than ECC, MI and NMI.

Crossing Fibers & Non-Tensor Approaches

13:30         3320.     Fibre Orientation Probability Maps from Q-Ball and the Model-Based Bootstrap – A Potential Segmentation Tool

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Hamied Ahmad Haroon¹, Karl V. Embleton¹, Geoff J M Parker¹

¹The University of Manchester, Manchester, UK

Model-based residual (MBR) bootstrap enables quantification of the uncertainty in the inferred fibre orientation for probabilistic fibre tracking using a single HARDI dataset. Here we present probability maps of observing n fibre orientations estimated by MBR bootstrapping over i iterations in every voxel. These maps provide information for the classification of tissues based on their microstructural orientation complexity. The probability of finding any given configuration reflects the underlying tissue microscopic complexity, macroscopic partial volume, and data noise levels. This information will be of use in probabilistic tractography and in monitoring changes in tissue complexity due to disease or developmental processes.

14:00         3321.     4th Order Diffusion Tensor Estimation and Application

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Aurobrata Ghosh¹, Maxime Descoteaux¹, Rachid Deriche¹

¹INRIA, Sophia Antipolis – Méditerranée, Sophia Antipolis, France

We review and compare the existing methods for 4th order diffusion tensor imaging. We also propose an extension to the Riemannian framework developed for classical 2nd order DTI to the space of 4th order tensors. We test the methods on synthetic HARDI data, and on real brain data. In conclusion our experiments confirm that our Riemannian extension is capable of detecting fiber crossings, is the only algorithm that guarantees positive definite diffusion and is also computationally viable to be practicable.

14:30         3322.     Denoising HARDI Coefficients Using Spherical Wavelet Lifting

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Sofia Olhede¹, Brandon Whitcher²

¹University College London, London, UK; ²GlaxoSmithKline, London, UK

We propose to estimate the diffusion distribution at each voxel by using a discrete wavelet transformation on the sphere, combined with an estimation procedure that is adapted to the Rician distribution.  To respect the underlying sampling scheme and avoid smoothing out details in Q-space we construct a discrete wavelet transform using lifting.

15:00         3323.     How Fast Can PAS Go?

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Ken Earl Sakaie¹

¹The Cleveland Clinic, Cleveland, Ohio, USA

High angular resolution diffusion imaging, combined with advanced postprocessing methods, can resolve crossing fibers. Of the large number of postprocessing methods, Persistent Angular Structure (PAS) has desirable properties in terms of angular resolution, accuracy, and robustness against noise, but the publicly available PAS calculation software can require weeks to months to analyze a typical brain dataset on a single processor. We show that coding the PAS calculation using widely available nonlinear optimization code can speed up the computation considerably, making this powerful method an option for more widespread use.

13:30         3324.     Bootstrap Methods for Estimating Uncertainty in Constrained Spherical Deconvolution Fiber Orientations

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Ben Jeurissen¹, Alexander Leemans², J-Donald Tournier³,⁴, Jan Sijbers¹

¹University of Antwerp, Antwerp, Belgium; ²School of Psychology, Cardiff University, Cardiff, UK; ³Brain Research Institute, Melbourne, Australia; ⁴University of Melbourne, Melbourne, Australia

Monte Carlo simulations were used to assess the accuracy and precision of bootstrap estimates of the uncertainty associated with brain white matter fiber orientations derived from diffusion weighted MRI using the new high angular reconstruction technique called constrained spherical deconvolution (CSD). We studied the accuracy and precision of these estimates as a function of repeated acquisitions, bootstrap realizations and inter-fiber angle. We showed an improvement of the accuracy of the uncertainty estimates of CSD fiber orientations, using an adaptation of the bootstrap called bootknife. Estimation of uncertainty is very important when fiber orientations are used in white matter fiber tractography, since errors are known to propagate.

14:00         3325.     CSF Partial Volume Effect for Diffusional Kurtosis Imaging

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Caixia Hu¹, Jens H. Jensen¹, Maria Fatima Falangola¹, Joseph A. Helpern¹

¹Center for Biomedical Imaging, New York, New York, USA

It is well known that CSF partial volume effects affect the fractional anisotropy (FA) and mean diffusivity (MD) values measured with diffusion tensor imaging (DTI).  Prior studies have shown how to assess this quantitatively by comparing results from conventional DTI with those from fluid-attenuated inversion recovery (FLAIR) DTI In this study, we applied a recent generalization of DTI called diffusional kurtosis imaging (DKI) to obtain measurements of FA, MD, and mean kurtosis (MK) in human brain with and without FLAIR and found MK to be a more robust measurement with regard to CSF contamination than either MD or FA.

14:30         3326.     Voxel Based Topometry of the ADC Profiles: Collapsing of the Dimensionality

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Oleg Petrovich Posnansky¹, Nadim Jon Shah¹

¹Institute of Neurosciences and Biophysics (Medicine), Research Centre Juelich, Juelich, Germany

We explore the complex geometry of the apparent diffusion coefficient (ADC) profiles and introduce a set of measures and their topological characteristics – non-integer dimensions. Using the step-by-step scale blowing sphere method we analyse the random spatial structure of the ADC profiles and present maps of indices obtained by the proposed algorithm. The maps correlate with the anatomical structure of the brain to different extents and provide more detail non-Gaussian information about brain architecture.

15:00         3327.     A Simple Method for ODF Reorientation After Deformable Imaging Registraton

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Jinsuh Kim¹, Madhura Ingalhalikar², Vincent A. Magnotta², Andrew L. Alexander³

¹University of Iowa, Iowa City, Iowa, USA; ²University of Iowa, USA; ³University of Wisconsin, Madison, Wisconsin, USA

We propose a simple and efficient method of orientation distribution function reorientation that allows correct estimation of fiber distribution by deforming high angular resolution diffusion imaging data and applied diffusion gradient direction based on the high dimensional transformation.

13:30         3328.     Comparison of Directional Diffusion Kurtoses and Diffusivities in EAE- Induced Spinal Cord

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Matthew Man Hin Cheung¹,², Edward Sai Kam Hui¹, Wutian Wu¹, Ed X. Wu¹

¹The University of Hong Kong, Pokfulam, Hong Kong

Understanding the complex pathology of MS is important in treatment strategies. In this experiment, diffusion kurtosis imaging (DKI) was applied to ex-vivo EAE rat spinal cord samples. The DK tensor and directional kurtoses were computed. The differences between the EAE and the normal were evaluated. The directional kurtosis analysis was shown to possess high sensitivity, thus potentially capable of better differentiating MS pathology and understanding the disease.

14:00         3329.     Diffusional Kurtosis Approximation of the Orientation Distribution Function in the Human Brain

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Mariana Lazar¹, Jens H. Jensen¹, Joseph A. Helpern¹

¹New York University School of Medicine, New York, USA

The Orientation Distribution Function (ODF) is used to describe the directionality of multimodal diffusion in regions with complex fiber architecture. Here, we present an approximation for the ODF of water diffusion from diffusional kurtosis imaging (DKI). The DKI-based ODF approximation is decomposed into two components representing the Gaussian and non-Gaussian (NG) diffusion contributions, respectively. Orientation maps obtained for in-vivo brain imaging data demonstrate multiple fiber components in brain regions with complex anatomy, with the NG-ODF being the most sensitive to profiling the fibers’ directions. The results appear to be in agreement with known white matter architecture.

14:30         3330.     Simulation Study of Kurtosis Measurements in MR Diffusion Kurtosis Imaging

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Kyle Ho Yiu Cheng¹,², Ed X. Wu¹

¹The University of Hong Kong, Pokfulam, Hong Kong

Monte Carlo simulation was performed in 1D space to study the spin diffusion, kurtosis characteristics, spin dephasing and MR signal attenuation in compartment-restricted diffusion environment. The apparent kurtosis was computed based on DKI formulation and compared to the true kurtosis and calculated from the actual diffusion displacement profiles. The simple results revealed that errors can be present in estimating true diffusion kurtosis by the apparent kurtosis. Choices of diffusion weighting parameters affect the outcomes. Both apparent diffusion kurtosis measurement and true diffusion kurtosis are not entirely intrinsic to the tissue structures because they also depend on the MR parameters.  Therefore, cautions must be taken in the quantitative interpretation of kurtosis measurements in DKI experiments.

15:00         3331.     Diffusion Kurtosis Imaging (DKI) of in Vivo Human Brain at 7 T

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Eric Edward Sigmund¹, Caixia Hu¹, Mariana Lazar¹, Maria Fatima Falangola¹, Jens H. Jensen¹, Joseph A. Helpern¹

¹New York University, New York, New York, USA

Diffusion kurtosis imaging (DKI) has been performed in healthy volunteer in vivo brain in a 7 T scanner and 24-channel head coil.  DKI  provides all of the information in DTI in addition to higher order structural contrast determined by non-Gaussian diffusion.  High parallel imaging factors were used to  mitigate high field EPI image artifacts.  Mean diffusivity MD, fractional anisotropy FA, and mean kurtosis MK were consistent with results at 3 T.  MD showed comparable white matter / gray matter values, FA was elevated in WM and negligible in GM, and MK was nonzero and distinct in both tissue types.

Restricted Diffusion

13:30         3332.     A Statistical Approach for Creating Anisotropy Maps of the Brain Using Q-Space Diffusion Weighted Images

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Siamak Pourabdollah-Nejad¹,², Quan Jiang¹,³, Douglas C. Noll², Guang Liang Ding¹, Michael Chopp¹,³

¹Henry Ford Hospital, Detroit, Michigan, USA; ²University of Michigan, Ann Arbor, Michigan, USA; ³Oakland University, Rochester, Michigan, USA

In this abstract, a new method for creating anisotropy maps of the brain in introduced. In this method q-space data of the brain is acquired and as a measure of anisotropy, the deviation of the diffusion vectors from a sphere is calculated and is used for creating the new map which we have named Standard-Deviation map. Comparison of our map with other conventional maps such as the FA map shows that the new map can identify regions with crossing fibers more realistically. We have validated our method with histology and q-space MR images of a rat with traumatic brain injury.

14:00         3333.     Probing Restricted Microcompartments with Double PGSE

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Noam Shemesh¹, Yoram Cohen¹

¹Tel Aviv University, Tel Aviv, Israel

The double PGSE (d-PGSE) sequence was used to study water diffusion in 20ìm microtubes. Indeed we found, as predicted by a recent simulation, that a negative diffraction pattern occurs. The results of non-collinear d-PGSE (i.e. d-PGSExz or d-PGSEzx ) were found to be identical and independent of the mixing time (tm). The signal decay and the diffraction patterns of the collinear directions (i.e. d-PGSExx) depend on tm. Future work in micro scale phantoms and neuronal tissues will demonstrate whether d-PGSE can overcome some of the limitations of s-PGSE experiments.

14:30         3334.     The Dependency of the MR Indices, Observed by High B-Value Q-Space Diffusion MRS on Fiber's Orientation

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Amnon Bar-Shir¹, Yoram Cohen¹

¹Tel-Aviv University, Tel-Aviv, Israel

The present study examines the effect of the rotational angle, α, on the apparent diffusion coefficient, extracted from low b-values and on the root mean square displacement (rmsd) of the fast- and the slow-diffusing components extracted from high b-value q-space MR diffusion experiments performed on optic nerves. The rmsd of the slow-diffusing component exhibits the most significant dependence on α. This phenomenon was found for both mature and newborn optic nerves and for short and long diffusion times. Our findings imply that the rmsd of the slow-diffusing component is the best predictor for restriction and fiber's orientation.

15:00         3335.     in vivo High Resolution Q-Space Imaging of the Spinal Cord Injury in Nonhuman Primates [Not Available]

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Keigo Hikishima¹,², Masaya Nakamura, Kanehiro Fujiyoshi, Masayuki Yamada,², Kazuya Kitamura, Suketaka Momoshima, Kazuo Yagi, Norikazu Tamaoki², Yoshiaki Toyama, Hideyuki Okano

¹Keio University School of Medicine, Sinjuku, Japan; ²Central Institute for Experimental Animals, Kawasaki, Japan

q-space imaging(QSI) enables us to detect the size of microstructure quantitatively and has been used gradually. However, there is no report about in vivo QSI of the spinal cord (SC) in Nonhuman primates. To evaluate the structural changes of the injured SC in the same animal longitudinally, we performed in vivo high resolution QSI of both intact and injured spinal cords in common marmosets and confirmed the accuracy of QSI through histology. As the results, high Resolution QSI map reflected the histological changes of the injured SC and was useful for its evaluation.

13:30         3336.     A Spectral Filtering View of Diffusion Gradient Encoding

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Andrew JM Kiruluta¹

¹Harvard University, Cambridge, Massachusetts, USA

Diffusion imaging gradients serve to spectrally filter the temporally evolving diffusion tensor in the spectral domain. In this formulation, the design of diffusion sensitizing gradients is reduced to the problem of adequately sampling q-space in the spectral domain and hence one of designing a suitable filter.  The practical limitations imposed by the requirement for delta function type diffusion sensitizing gradients to adequately sample q-space, can be relaxed if these impulse gradients are replaced with chirped oscillatory gradients.

14:00         3337.     A Two-Compartment Model to Accurately Characterize Extra- And Intra-Cellular Spaces in Neural Tissue with Q-Space Imaging

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Henry H. Ong¹, Felix W. Wehrli¹

¹University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA

Knowledge of white matter (WM) intra-cellular volume fraction and mean axon diameter (ICF and MAD) would provide important insight into injury and pathology. Q-space imaging (QSI) offers potential for indirect assessment of WM architecture but is complicated by signal from both extra- and intra-cellular spaces  (ECS and ICS). Here, we use a two-compartment model to fit QSI molecular displacement distribution profiles from WM tracts in healthy mouse spinal cords to characterize the ECS and ICS. The measured ICF and MAD values showed excellent agreement with histology and demonstrate the feasibility of this method to extract non-destructively accurate WM architecture information.

Methods for Brain Arterial Spin Labelling

13:30         3338.     Reliability and Reproducibility of Arterial Spin Labeling Perfusion Measures Assessed with a Multi-Center Study

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Thomas Liu¹, Christina Wierenga², Bryon Mueller, Jiong Jiong Wang, Gary Glover, James Voyvodic, Doug Greve, Jessica Turner, Cynthia Wible, Greg Brown, Function BIRN

¹UCSD Center for Functional MRI, La Jolla, California , USA; ²UCSD Dept. of Psychiatry, La Jolla, California , USA

Arterial spin labeling MRI was used to obtain whole brain cerebral blood flow measures in a sample of 11 healthy volunteers who were scanned at three different sites participating in the Function BIRN study.  There was not a significant effect of site on the cerebral blood flow measures, but there was a significant effect of subject.

14:00         3339.     Pseudo-Continuous Arterial Spin Labeling at 7T

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Wen-Ming Luh¹, Tie-Qiang Li¹, Eric C. Wong², Peter A. Bandettini¹

¹National Institutes of Health, Bethesda, Maryland, USA; ²University of California, San Diego, La Jolla, California , USA

Arterial spin labeling (ASL) techniques benefit from the increase in T1 at high field strength. However, the SNR improvement at high field can only be realized with an optimal tag duration which also increases with field strength. At 7T, the optimal tag duration can reach 3 and 1.3 sec for continuous and pulsed ASL, respectively.  Pseudo-continuous ASL allows for long tag duration without special hardware. However, both B1 and B0 inhomogeneity with the volume excitation coil toward the tagging location presents challenges for PCASL. Here we implemented PCASL at 7T and demonstrated these effects and a way to mitigate them.

14:30         3340.     Mapping PASL Arterial Transit Time in Normal Human Brain Using [15O]water  PET

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Maolin Qiu¹, J Wang¹, H Kim¹, R E. Carson¹, R T. Constable¹

¹Yale University School of Medicine, New Haven, Connecticut, USA

Arterial transit time (ATT) in pulsed arterial spin labeling (PASL) refers to the time it takes the arterial blood to travel from the labeling site to the capillaries. It defines the earliest time data acquisition could start after IR labeling and is required for CBF quantification. ATT measurements that use the PASL sequence suffer from the low sensitivity of PASL and intravascular contamination. ATT is usually determined and used on a per-slice basis and within slice variations in ATT are not considered. The use of improper ATT values can introduce errors in CBF quantification. In this study we used CBF measured by PET to calculate the ATT on a per-voxel basis, which allows us not only to examine the in-slice ATT variability, but also to optimize the imaging parameters for PASL. More important, the ATT map, once estimated, can be used for CBF mapping in a similar PASL imaging setup, providing voxel based ATT values.

15:00         3341.     Tagging Efficiency Improvement Using Velocity-Matched Pseudo-Continuous Arterial Spin Labeling and VERSE

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Wen-Ming Luh¹, Eric C. Wong², S Lalith Talagala¹, Peter A. Bandettini¹

¹National Institutes of Health, Bethesda, Maryland, USA; ²University of California, San Diego, La Jolla, California , USA

Pseudo-continuous arterial spin labeling can be performed with standard commercial scanners without special hardware. Moreover, several characteristics of the RF and gradient pulses can be adjusted for optimal performance. However, changes in velocity through the cardiac cycle can compromise tagging efficiency especially during systolic phases. It is possible to improve tagging efficiency for high velocity spins by increasing RF amplitude at the cost of SAR. Fortunately, the increase in SAR can be mitigated with VERSE transformation if needed. Here we dynamically raised PCASL RF amplitude according to the measured velocity profile at labeling location with cardiac gating and VERSE modification.

13:30         3342.     Influence of Cardiac Cycle on Velocity Selective Arterial Spin Labeling

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Wouter M. Teeuwisse¹,², Mark A. van Buchem¹, Matthias J. van Osch¹

¹Leiden University Medical Center, Leiden, Netherlands

In velocity selective arterial spin labeling (VS-ASL), blood that flows faster than a predetermined cut-off velocity is labeled. Because blood velocity is not constant, labeling efficiency may vary over cardiac cycle. In this study, dependency of perfusion signal on cardiac cycle was investigated. VS-ASL was performed with cardiac triggering at various trigger delays. In all volunteers mean slice perfusion showed variation up to ± 20% compared to mean perfusion with trigger delay at diastole. Variation over cardiac cycle was different between subjects. When cardiac triggering is applied, a trigger delay of 300 ms gives highest label efficiency in most cases.

14:00         3343.     Achieving Late Inflow Delay in Pseudo-CASL 3D GRASE Using a Hybridized Labeling and Background Suppression Scheme

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María A. Fernández-Seara¹, Jiongjiong Wang², David A. Feinberg³, John A. Detre²

¹Center for Applied Medical Research, University of Navarra, Pamplona, Spain; ²University of Pennsylvania Medical Center, Philadelphia, Pennsylvania, USA; ³Advanced MRI Technologies, Sebastopol, California , USA

A modified version of the pseudo-CASL background suppressed 3D GRASE sequence is presented. This sequence, which allows acquisition of perfusion maps with long post-labeling delay, in a short scan time, will be useful in cases in which arterial transit time is prolonged as occurs in cerebro-vascular disease or acute stroke.

14:30         3344.     An Efficient Labeling Scheme for CASL for Use with Multiple, Independently Switched Coils

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Ralf Berthold Loeffler¹, Ruitian Song¹, Yong Zhang¹, Adam Martin Winchell¹,², Josef Pfeuffer³, Zoltan Patay¹, Claudia Maria Hillenbrand¹

¹St. Jude Children's Research Hospital, Memphis, Tennessee, USA; ²University of Memphis and UTHSC Joint Biomedical Engineering Program, Memphis, Tennessee, USA; ³Siemens Medical Solutions, Erlangen, Germany

A new paradigm for efficient multi-coil continuous arterial spin labeling is presented. The paradigm utilizes signal from every excitation to calculate the contribution of a particular artery. The paradigm was implemented on a standard clinical scanner for 3 label coils, which led to a paradigm length of 8. The label coils could be switched independently by a custom built RF cabinet that was controlled by the scanner. Volunteer measurements demonstrated good separation of vascular territories in the brain.

15:00         3345.     Continuous Artery-Selective Spin Labeling (CASSL) Applied to Distal Branches of Intracranial Arteries

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Michael Helle¹,², David Norris², Karsten Alfke¹, Olav Jansen¹

¹Christian-Albrechts-Universität, Kiel, Germany; ²FC Donders Centre for Cognitive Neuroimaging, Nijmegen, Netherlands

We demonstrate the feasibility of CASSL to selectively label blood of individual branching intracranial arteries even in the immediate vicinity of other small vessels in-vivo. A saturation of the magnetization in non-selected vessels depends basically on the labeling gradient orientation, its rotation frequency and the distance from the labeling focus. By empirical optimization of these key parameters the labeling of small arteries with diameters of 3 mm and less,  that branch from the media and anterior cerebral arteries, mainly to A2/A3 and M2/M3 segments respectively, is demonstrated.

13:30         3346.     A Simple Model to Measure Arterial Cerebral Blood Volume by Arterial Spin Labelling

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Roman Weso&#322;owski¹, Penny A. Gowland¹, Susan T. Francis¹

¹University of Nottingham, Nottingham, UK

A method of quantifying LL-FAIR data for arterial cerebral blood volume (CBVa) using simple correction factors is described. Monte-Carlo simulations are used to compare the results of fitting CBVa using this simplified method with the standard stepwise compartment model based on Bloch equations. We have used the new method to quantify (CBVa) from experimental LL-FAIR data acquired at 3 T during a 4.8 s visual stimulus.

14:00         3347.     A Probabilistic Approach to Model-Free Arterial Spin Labeling Perfusion Quantification

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Michael A. Chappell¹, Salima Makni¹, Saad Jbabdi¹, Mark W. Woolrich¹

¹University of Oxford, Oxford, UK

Traditional 'kinetic curve' model based methods for ASL analysis are not ideal for perfusion quantification in pathological tissue, since assumptions about healty tissue are made in the models. Recently the 'model-free' approach to ASL analysis has been demonstrated, this treats the signal as the convolution of an arterial input and redsidue function. Here we present an improved probabilistic based method for model-free ASL analysis. The advantage of this approach is that residue function shape can be determined under the constraint of temporal smoothness, without neededing to set the functional form a priori and without the regularisation aretefacts of a singular value decomposition approach. The method also includes a procdure to determine arterial feeding regions, for arterial input function assignment, based on blood arrival time information. Ultimately the method is designed to provide robust perfusion measurments from ASL data even in pathological tissue.

14:30         3348.     Post-Processing Correction for Extended Data Acquisition in Whole Brain 3D Quantitative PULSAR Imaging

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Neville Dali Gai¹, John Anthony Butman¹

¹National Institutes of Health, Bethesda, Maryland, USA

Here we devise a simple first-order correction scheme for extended data acquisition 3D PULSAR brain perfusion imaging. Extended data acquisition (~600ms) introduces some ambiguity in the transit time used in quantitative CBF determination. By applying an exponential correction for tagged blood decay in hybrid space, we attempt to reduce bolus dispersion effects during acquisition. Corrected values were compared with corresponding single slice imaging. CBF values in 3D slices were lower than corresponding single slice acquisition values due to blurring. However, after correction the values showed better agreement with the single slice acquisition case.

15:00         3349.     Comparison of Quantitative Perfusion 3D IR-PULSAR  with Multi-Slice 2D and Single Slice Imaging

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Neville Dali Gai¹, Sardha Lalith Talagala¹, John Anthony Butman¹

¹National Institutes of Health, Bethesda, Maryland, USA

In this study, CBF values obtained with extended 3D data acquisition (for whole brain coverage) QUIPSSII IR-PULSAR are compared with values obtained with multi-slice 2D (MS-2D) and single slice acquisition. Excellent agreement in gray matter (GM) global average CBF values was found between the 3D and 2D-MS acquisition schemes. There was good agreement between the GM CBF values from 3D slices and corresponding single slice acquisitions. Values were slightly lower in the 3D case due to blurring. White matter CBF values were very low for all acquisition schemes due to much longer transit delays (~1.6s). Whole brain quantitative perfusion imaging with 3D PULSAR is feasible as long as the above limitations are kept in mind.

Diffusion Acquisition

13:30         3350.     Simulations of SNR Efficiency of DTI Using Parallel Imaging and RFOV Acquisition at 3 T and 7 T [Not Available]

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Carolin Reischauer¹, Robert Stefan Vorburger¹, Bertram Jakob Wilm¹, Thomas Jaermann¹, Philipp Staempfli¹, Peter Boesiger¹

¹ETH and University of Zurich, Zurich, Switzerland

The transition to ultra-high field strengths promises a boost in the SNR for diffusion tensor imaging. Image acquisition typically relies on single-shot EPI which is hampered by susceptibility-induced distortions and T2* related blurring, especially at high field strengths. These challenges can be quite effectively addressed by partial Fourier and reduced FOV acquisition, as well as parallel imaging methods. In the present work simulations at 3 T and 7 T were performed to investigate under which conditions the SNR gain can be tapped, provided that higher reduction factors have to be applied at ultra-high field strengths.

14:00         3351.     Apparent Diffusion Behaviors Modulated by Distant Dipolar Field in Solution NMR

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Shuhui Cai¹, Guiping Shen¹, Congbo Cai¹, Zhong Chen¹

¹Xiamen University, Xiamen, People's Republic of China

A modified CRAZED sequence was designed to observe and characterize apparent diffusion behaviors of signals from intermolecular double-quantum coherences during the mixing period. It is found that their apparent diffusion behaviors are different from conventional single-quantum coherences, and different orientation of diffusion weighting gradients relative to coherence selection gradients results in different apparent diffusion behaviors. This indicates that the apparent diffusion behavior is influenced by the distant dipolar field.

14:30         3352.     Optimizing Diffusion Measurements for Large-Scale Multi-Centre Trials: A Magnims DT MRI Sequence

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Elisabetta Pagani¹, Jochen G. Hirsch², Marco Rovaris¹, Achim Gass², Petra Pouwels³, Stephan Roosendaal³, Frederik Barkhof³, Federica Agosta¹, Domenico Caputo⁴, Antonio Giorgio⁵, Jacqueline Palace⁵, Silvia Marino⁶, Nicola De Stefano⁶, Massimo Filippi¹