In Vivo Oxygen-17 (17O) MRI at 7 Tesla
Stefan Hoffmann¹, Paul Begovatz¹, Armin Nagel¹, Reiner Umathum¹, Michael Bock^1
1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany

The detection of oxygen-17 (17O) provides a method to assess metabolic tissue information at ultra high fields. In this work direct 17O-MR imaging was carried out in vivo on a 7 Tesla MR system with a custom built head coil. Natural abundance imaging of the human head was performed and global relaxation parameters were measured. An inhalation experiment with enriched 17O gas was carried out using an inhalation-triggered oxygen delivery system. Imaging was performed prior to, during and after the inhalation showing an increase of signal intensity during ventilation with enriched oxygen-17 gas.

3D Regional Measurements of Alveolar Surface Area Using 90° Single Breath XTC
Samuel Patz¹, Iga Muradyan¹, Mikayel Dabaghyan¹, Isabel Maria Dregely², Mirko I. Hrovat³, Hiroto Hatabu¹, F William Hersman⁴, Iulian C. Ruset⁴, James P. Butler^5
1Department of Radiology, Brigham and Women's Hospital, Boston, MA, United States; ²Department of Physics, University of New Hampshire, Durham, NH, United States; ³Mirtech, Inc, Brockton, MA, United States; ⁴Xemed, LLC, Durham, NH, United States; ⁵Department of Environmental Health, Harvard School of Public Health, Boston, MA, United States

Alveolar surface area is a key determinant of the severity of emphysema. Hence it is important to obtain regional maps of this parameter in order to evaluate disease heterogeneity. To accomplish this goal, we obtained 3D regional measurements of alveolar surface area per unit volume by measuring the septal uptake of hyperpolarized ¹²⁹Xe. Single Breath XTC was used but 90° RF pulses were used for the selective “tissue phase” pulses rather than the traditional 180° pulses.

Indirect ¹⁷O MRI Using T1ρ at 11.7 T
Hsiao-Ying Wey^1,2, Fang Du¹, Ai-Ling Lin¹, Yen-Yu I. Shih¹, Saaussan Madi³, Peter T. Fox^1,2, Pradeep M. Gupte⁴, Timothy Q. Duong^1,2
1Research Imaging Institute, UT Health Science Center at San Antonio, San Antonio, TX, United States; ²Radiology, UT Health Science Center at San Antonio, San Antonio, TX, United States; ³Bruker Biospin MRI, Inc., Billerica, MA, United States; ⁴Rockland Technimed Ltd., Airmont, NY, United States

Cerebral metabolic rate of oxygen (CMRO₂) is an important physiological parameter associated with normal brain and disease state. The unique characteristic of ¹⁷oxygen makes ¹⁷O MRI a valuable tool for CMRO₂ quantification. Direct ¹⁷O measurement suffers from low spatiotemporal resolution and clinical practicability compared to indirect method, although the quantification is more straightforward. This study demonstrates the feasibility of indirect T1ρ-weighted ¹⁷O detection with ¹⁷O/PFC blood substitute injection in normal and physiologically modulated (hypothermia and ischemic stroke) rats at ultra-high field.

Separation of Sodium Compartments for Characterization of Tumor Tissue by ²³Na-MRI
Armin Michael Nagel¹, Michael Bock¹, Christian Matthies¹, Marc-André Weber², Stephanie Combs³, Wolfhard Semmler¹, Armin Biller, ^2
1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany; ²Department of Diagnostic and Interventional Radiology, University Hospital Heidelberg, Germany; ³Department of Radiation Oncology, University Hospital Heidelberg, Germany

In this work brain-tumor patients were investigated with different ²³Na-image contrasts (spin-density, ²³Na-FLAIR)  to gain information from which compartment the ²³Na-signal originates. Using a ²³Na-FLAIR sequence different ²³Na-compartments in many brain tumors can be suppressed, whereas other parts still exhibit a high ²³Na-FLAIR-signal. Our findings indicate that a combination of both ²³Na-sequences allows for separating different ²³Na compartments. Distinguishing these compartments might be important for the determination of potential tumor malignancy.

In Utero MRI of Cerebral Vascular Development in Mice
Cesar Augusto Berrios-Otero¹, Brian J. Nieman², Daniel H. Turnbull^1,3
1Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, United States; ²Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada; ³Department of Radiology, New York University School of Medicine, New York, United States

Vascular system development involves a complex, three-dimensional branching process that is critical for normal embryogenesis. In a previous study, we developed a contrast-enhanced perfusion method to selectively enhance the cerebral arteries in fixed mouse embryos and demonstrated that Gli2 mutant mice lack a basilar artery, a key arterial input to the posterior brain regions. However, imaging studies of Gli2 and many other mutant mice with vascular defects are limited because mice do not survive postnatally. Extending vascular imaging to an in utero setting with potential for longitudinal vascular development studies is an exciting possibility. However, in vivo MRI scans routinely result in undesirable image artifact due to subject motion. In this study we utilized an in utero imaging, which corrects for motion using an interleaved gating acquisition and serial comparison of rapidly acquired 3D images. We demonstrate the potential of this method by examining vascular development in utero in E17.5 wildtype and Gli2 mutant mice. We show that the in vivo methods produce high-quality images of the embryonic cerebral vasculature and are able to detect the basilar artery phenotype in Gli2 mutants.

Cardiac Purkinje Fiber Imaging: The First Instance of in Situ Visualization of the Conduction Path Using MR Microscopy
Min Sig Hwang¹, Katja Odening², Ohad Ziv², Bum-Rak Choi², Gideon Koren², John R. Forder^1
1McKnight Brain Institute, University of Florida, Gainesville, FL, United States; ²Cardiovascular Research Center, Rhode Island Hospital Alert Medical School of Brown University, Providence, RI, United States

In this study, we performed high resolution MR imaging using a 17.6 T magnet to demonstrate the cadiac conduction pathways as well as anatomical details of isolated rabbit hearts.  The volume rendered images from the original 3D MR data, achieving a 35 ¥ìm in-plane resolution and generating an adequate T2*-weighted image constrast, made it possible to non-invasively and reproducibly trace the conduction paths in the left and right ventricles, as well as to describe the micro-anatomical make-up of the whole heart.

In Vivo Ultra High Field Magnetic Resonance Microimaging to Track the Development of Malignant Melanoma in Zebrafish
A. Alia¹, S. Kabli¹, S. He², E. S. Jagalska², A. Hurlstone³, H. P. Spaink², H. J. M. de Groot^1
1Leiden Institute of Chemistry, Leiden University, Leiden, Netherlands; ²Institute of Biology, Leiden University, Leiden, Netherlands; ³Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom

Zebrafish cancer models are fast gaining ground in cancer research. Most tumors in zebrafish develop late in life, when fish are no longer transparent, limiting in vivo optical imaging methods. Thus, non-invasive imaging to track tumors in adult zebrafish remains challenging. In this study tumors were visualized in transgenic zebrafish using µMRI at 9.4T.  Furthermore, live imaging of tumors at ultra-high field (17.6T) revealed significant tumor heterogeneity. This study demonstrating the application of μMRI to detect the locations, invasion status and characteristics of internal melanomas in zebrafish and pave the way for tracking tumor development and real-time assessment of therapeutic effects in zebrafish tumor models.

Phase Contrast Based MR Microscopy of Glial Tumor Cells Using Microcoils
Nicoleta Baxan¹, Ulf Kahlert², Hans Weber¹, Mohammad Mohammadzadeh¹, Juergen Hennig¹, Dominik von Elverfeldt^1
1Diagnostic Radiology, Medical Physics, University Hospital, Freiburg, Germany; ²Stereotactic Neurosurgery, University Hospital , Freiburg, Germany

The contrast mechanism employed for differentiating structures in micron-scale samples is of great interest especially when is combined with high-resolution MRI and an adequate SNR. In this study, phase contrast together with the susceptibility weighted imaging (SWI) technique was performed for imaging living glial tumor cells. Our method combines the benefits of exploiting the phase MR signal for contrast enhancement and the sensitivity optimization by using MR microcoils. Biochemical spectroscopy investigations were performed as well within a timeframe not detrimental for preserving cells viability.

In Vivo Imaging of Redox State in Mice Using EPRI/MRI Coimaging - not available
George Laurentiu Caia¹, Ziqi Sun¹, Sergey Petryakov¹, David Johnson¹, Murugesan Velayutham¹, Alexander Samouilov¹, Jay Louis Zweier^1
1Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University, Columbus, OH, United States

Electron  paramagnetic resonance imaging (EPRI)  using nitroxide spin probes is a sensitive technique for in vivo measurement of redox state. 1D and 2D EPR imaging has been previously used to map and monitor the change in redox status of various organs in animal models. However, 3D EPR imaging of the change in redox status in vivo with anatomic registration is essential to understand organ specific pathology and disease. In the present work, the nitroxide 3-carbamoyl-2,2,5,5-tetramethyl-1-pyrrolidinyl-N-oxyl (3CP) was used to map and monitor the redox state of various organs in living mice using the new EPR/NMR coimaging instrumentation [1]. With rapid scan projection acquisition, we performed 3D mapping of 3CP in living mice every 8 minutes. The NMR coimaging allowed precise slice by slice measurement of the radical reduction and mapping of this metabolism in major organs such as the heart, lungs, liver, bladder and kidneys.

Assessment of Melanoma Extent and Melanoma Metastases Invasion Using Electron Paramagnetic Resonance and Bioluminescence Imaging
Quentin Godechal¹, Florence Defresne², Philippe Leveque¹, Jean-François Baurain³, Olivier Feron², Bernard Gallez^1
1Biomedical Magnetic Resonance Unit, Université Catholique de Louvain, Bruxelles, Belgium; ²Pharmacotherapy Unit, Université Catholique de Louvain, Bruxelles, Belgium; ³Medical Oncology Unit, Université Catholique de Louvain, Bruxelles, Belgium

Malignant melanoma is a skin tumor characterized by the uncontrolled proliferation of melanocytes, which can lead to metastasis mainly in lungs. The incidence of melanoma is rising each year. For this reason, it is essential to develop new effective methods able to detect melanoma. The purpose of the present study is to assess the ability of EPR to detect and measure the colonization of lungs by melanoma metastases. Results will be compared to results obtained with bioluminescence imaging in order to validate the EPR method.