Session 83: Microscopy & Perfusion Imaging

Microscopy & Perfusion Imaging

Friday 24 April 2009

Room 315

10:30-12:30

Moderators:

Rakesh Sharma and Jeffrey L. Zhang

10:30	*822.*	Sub-Nanoliter Microscopic MR Imaging of the Human Skin in Vivo Using a 12 Mm Superconducting Surface Coil at 1.5 Tesla
		Elmar Laistler^1,2, Marie Poirier-Quinot², Jean-Christophe Ginefri², Simon Lambert², Rose-Marie Dubuisson², Emeline Boriasse², Ewald Moser¹, Luc Darrasse^2 1MR Centre of Excellence, Medical University of Vienna, Vienna, Austria; ²U2R2M CNRS UMR8081, Université Paris Sud, Orsay, France
		We use a high temperature superconducing surface coil with a diameter of 12 mm to depict the human skin's pertinent structures in vivo at 1.5 T at an isotropic spatial resolution of (80 µm)³ corresponding to a voxel volume of 0.51 nl. Different anatomical structures of the skin can be identified with sufficient SNR at scan times of ~10 min.

10:42	*823.*	Diffusion Weighted Imaging of Human Articular Cartilage Using Fractional Calculus Model: Preliminary Study
		Xu Feng¹, Richard L. Magin¹, Jun Li², Carol Muehleman^2 1Bioengineering, University of Illinois at Chicago, Chicago, IL, USA; ²Biochemistry, Rush Medical College, Chicago , IL, USA
		Restricted diffusion doesn't follow the mono-exponential decay. Some reports have suggested using bi-exponential model. However, bi-exponential fitting is nontrivial and needs some experience to get fast and slow diffusion coefficients. In this paper, we generalize a spatial Laplacian in the Bloch-Torrey equation to incorporate a fractional order Brownian model of diffusivity. A new parameter ¦Â was derived from the new equation of Stejskal-Tanner gradient pulses. We fitted the signal attenuation obtained from the diffusion-weighted images of Sephadex gels and human articular cartilages using fractional order diffusion model. The results show that ¦Â can be used to reflect the structure of the tissue. The ¦Â value obtained from the osteoarthritis (OA) cartilage was larger than from the normal cartilage. Future development of this approach may be useful for detecting the early degeneration of OA.

10:54	*824.*	Hypoxic Environments and the Extracellular Matrix: MRI and Second Harmonic Generation Microscopy Studies
		Samata m. Kakkad¹, Meiyappan Solaiyappan¹, Kristine Glunde¹, Brian O’Rourke², Arvind Pathak¹, Venu Raman¹, Marie-France Penet¹, Zaver M. Bhujwalla^1 1JHU ICMIC Program, The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA; ²Institute of Molecular Cardiobiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
		The tumor microenvironment plays an important role in several of the phenotypic traits of cancer. Hypoxia, in particular, leads to drug resistance, radiation resistance, and the selection of a more aggressive phenotype. The relationship between hypoxia, and the transport of macromolecules through the interstitial matrix in vivo is largely unexplored. The purpose of these studies was to determine if hypoxia alters the interstitial fluid transport of macromolecules by altering collagen fiber patterns.

11:06	*825.*	Phenotyping in the Mouse Embryo Using a μMRI Atlas
		Jon Orlando Cleary^1,2, Marc Modat³, Anthony Nathan Price¹, Nicholas D. Greene⁴, David L. Thomas^2,5, Peter J. Scambler⁶, Roger J. Ordidge^2,5, S Ourselin³, Mark Francis Lythgoe^1 1Centre for Advanced Biomedical Imaging, Department of Medicine and Institute of Child Health, University College London, London, UK; ²Department of Medical Physics and Bioengineering, University College London, London, UK; ³Centre for Medical Image Computing, University College London, London, UK; ⁴Neural Development Unit, UCL Institute of Child Health, London, UK; ⁵Wellcome Trust Advanced MRI Laboratory, University College London, London, UK; ⁶Molecular Medicine Unit, UCL Institute of Child Health, London, *equal contribution
		Voxel and deformation-based morphometry can detect subtle anatomical differences by combining a number of subjects to create an average atlas and comparing two atlases statistically. Studies of adult mouse brain have used these methods but they may be useful for phenotyping the mouse embryo. µMRI is an emerging technique for imaging mouse embryos. However current analysis involves inspection of each embryo. Morphometric methods, where large numbers of embryos may be compared, show promise for high-throughput analysis. We present an initial study to examine the viability of an embryo atlas, focusing on the degree of anatomy preserved after averaging individual embryos.

11:18	*826.*	MRI and OPT Comparison for Mouse Embryonic Development
		Michael David Wong¹, Jacob Ellegood¹, Jun Dazai¹, X Josette Chen¹, R. Mark Henkelman^1 1Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada
		The soft tissue contrast in MRI makes it a candidate for observing the normal development of the mouse embryo along with genetic abnormalities that may affect organogenesis. This study compares MR imaging of mouse embryos with images from another three-dimensional high-resolution imaging modality, Optical Projection Tomography (OPT). OPT and MR images of embryos are compared at equivalent stages of development: in the beginning organogenesis (E9.5), during organ growth (E11.5), and at organ maturity (E15.5).

11:30	*827.*	*True MR Microscopy on a Clinical 7 Tesla Scanner: Application to Plaque Detection in Ex Vivo* HCHWA-D Samples**
		Andrew Webb^1 1Radiology, Leiden University Medical Center, Leiden, Netherlands
		A flexible MR microscopy probe has been constructed to obtain high resolution isotropic images on a clinical 7 tesla scanner of plaques in ex vivo brain specimens from individuals who have had hereditary cerebral haemorrhage with amyloidosis-Dutch type, a form of Alzheimers disease. Images acquired at a spatial resolution of 40 x 50 x 100 microns show individual iron-containing plaques, which both confirm previous results obtained at much poorer spatial resolution, but also add detailed information on the biodistribution of these plaques.

11:42	*828.*	MR Microscopy of Human Skin Vasculature in Vivo at 3 Tesla Using a Small Copper Surface Coil
		Elmar Laistler¹, Ewald Moser^1 1MR Centre of Excellence, Medical University of Vienna, Vienna, Austria
		We show that using small surface coils and 3D GE sequences, imaging of the human skin in vivo with an isotropic resolution of (100 µm)³ is feasible at reasonable scan times with normal conducting surface coils at 3 T. Small cutaneous and subcutaneous vessels are well delineated and SNR is sufficient for manual segmentation. At such high spatial resolutions, subject motion is one of the limiting factors for good image quality. Using rather short sequences (~10min) limits motion artifacts. SNR loss due to the short measurement time can be compensated for by averaging over multiple acquisitions after coregistration.

11:54	*829.*	MRI Tissue Window Chamber System for Validation and Optimization of Dynamic Contrast Enhanced Tumor Imaging
		Olivier Maciej Girard^1,2, Ahmet Erten^2,3, Mark Bydder¹, Milan T. Makale², David A. Cheresh², David Gilderdale⁴, Sadik Esener^2,3, Robert Frederick Mattrey^{1,2 1}Department of Radiology, University of California, San Diego, CA, USA; ²Moores Cancer Center, University of California, San Diego, CA, USA; ³Electrical Engineering , University of California, San Diego, CA, USA; ⁴PulseTeq, UK
		Magnetic Resonance Imaging (MRI) holds significant promise to achieve quantitative analysis of tumor vasculature. However with deep tumor MRI there is no means by which to validate in vivo methods and results, especially those of a dynamic nature. We report here on the design and fabrication of a MRI and light microscope compatible window chamber, and initial time course data following Gd injection. Such a system is a significant step toward validation of permeability measurement by MRI with the light microscope.

12:06	*830.*	Blood Volume Fraction Measurements Using MRI: A Correlation Between Two-Photon and in Silico MR Estimates
		Thomas Christen^1,2, Nicolas Joudiou^1,2, Raphael Serduc^1,2, Gregoire Malandain³, Nicolas Pannetier^1,2, Jean-Claude Vial^1,2, Christoph Segebarth^1,2, Chantal Rémy^1,2, Emmanuel L. Barbier^{1,2 1}Inserm, U836, Grenoble, F-38043, France; ²Université Joseph Fourier, Grenoble Institut des Neurosciences, UMR-S836, Grenoble, France; ³Asclepios team, INRIA, Sophia-Antipolis, France
		The aim of this study is to evaluate the accuracy of MR estimates of Blood volume fraction (BVf). Brain cortical microvascular networks were digitized using a two-photon microscope. BVf was then obtained in two ways. First, BVf was quantified from the microscopic data using morphologic tools. Second, a steady-state MR protocol designed for measuring BVf was performed in silico. Comparison of BVf estimates obtained with the two techniques indicates that they are well correlated. However results show a systematic error (20% on average) on absolute quantification, possibly induced by approximations in modelling the microvascular network in MR.

12:18	*831.*	An Oxygen Consuming Phantom for Simulating Oxygen Perfusion in Tissue Using ¹⁹F MRI Oximetry
		Steven H. Baete^1,2, Yves De Deene^{1,2 1}1Laboratory for Quantitative Nuclear Magnetic Resonance in Medicine and Biology, ECNURAD, Ghent University, Ghent, Oost-Vlaanderen, Belgium; ²Medisip-IBBT, Ghent University, Ghent, Oost-Vlaanderen, Belgium
		Tumor hypoxia is well known to reduce cancer treatment efficacy. ¹⁹F MRI oximetry can be used to map oxygen concentrations in hypoxic tissue. However, validation of pO₂-measurements in vivo is difficult. In this study, an oxygen consuming phantom simulating oxygen perfusion in tissue is presented. The phantom consists of a hemodialysis filter of which the outer compartment is filled with a gel containing viable yeast cells. pO₂-images reveal oxygen consumption by the yeast after injection of a bolus of oxygen rich hexafluorobenzene in the fibers of the hemodialysis filter. The phantom can be used for validation of ¹⁹F MRI oximetry.