|Tissue Characterization Using MR Microscopy|
New Techniques for 3D, High-Resolution, Whole Brain
Mapping of Murine Vasculature
Arvind P. Pathak1, Melina Jones1, Jiangyang Zhang1
1The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
Knowledge of the 3D architecture of blood vessels is crucial because neuropathologies ranging from alzheimers disease to brain tumors involve anomalous blood vessels, and development of transgenic mouse models of disease has created a need to characterize the cerebral vasculature. While histological techniques such as optical microscopy and corrosion casting are excellent for imaging microvasculature at submicron resolutions, they suffer from limited coverage, and 3D blood vessel geometry once destroyed by sectioning requires complex reconstruction. Here we describe two novel methods for “whole brain” mapping of murine vasculature using magnetic resonance microscopy to obtain exquisite images with different “physiological stains”.
Empirical Estimation of Intra-Cellular Volume
Fraction in Mouse Spinal Cord with Q-Space Diffusion MRI
Henry H. Ong1, Felix W. Wehrli1
1University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
Knowledge of white matter intra- and extra-cellular volume fraction (ICF and ECF) would provide important insight into injury and pathology. Current diffusion MRI techniques measure ICF by numerically solving a difficult ill-posed Laplace inversion of the signal decay or fitting the decay to a model, which requires assumptions of the system. Recently, an experiment has been proposed to empirically measure ICF based on the different dependences on diffusion gradient length of restricted and Gaussian diffusion of the ICF and ECF, respectively. Here, we apply this technique to quantify ICF of healthy mouse spinal cords and compare the data to histology.
Detection of Embryonic Heart Motion in
the Mouse Using Self-Gated MRI
Brian J. Nieman1, 2, Daniel H. Turnbull1
1New York University School of Medicine, New York, USA
Self-gated imaging methods permit collection of motion sensitive data for use in artifact correction or gating without the need to interrupt image acquisition for additional radiofrequency or gradient events. These methods are attractive for implementation in studies involving mice, due to their small size, or wherever external measures are cumbersome or unavailable. In this abstract, we explored the possibility that a self-gated method would permit detection of embryonic cardiac events in utero and show calculated physiological traces correlate with the heart cycle, suggesting that cine cardiac MRI of the mouse in utero should be possible.
Determining Cellular Microstructure of Isolated Rat
Hearts Using Correlated Time-Dependent Diffusion and T2 Relaxation
Tina Pavlin1, Morten Bruvold1, Per Jynge1, John Georg Seland1
1Norwegian University of Science and Technology, Trondheim, Norway
The aim of this work was to study compartmentation and water diffusivity in isolated rat hearts by correlating time-dependent diffusion coefficient and T2 relaxation constant. Compartmental diffusivity enabled us to obtain structural information about the intra- and extra-cellular compartments in rat myocardium. Using a short-time diffusion model and assuming a cylindrical geometry of myocardial cells, we estimated the diameter of the cells to be 35 µm, and the inter-cell distance to be 20 µm.
|11:18||288.||Diagnostic Impact of T2* MRI Imaging for Improved Ex
Vivo Classification of Complicated Plaques
Timo Spehl1, Dominik Paul1, Michael Markl1, Dominik von Elverfeldt1, Heike Göbel1, Alex Frydrychowicz1, Andreas Hetzel1, Cornelius Weiller1, Joachim Schöllhorn1, Jürgen Hennig1, Andreas Harloff1
1Albert-Ludwigs Universität, Freiburg, Germany
The composition of high-grade internal carotid artery (ICA) stenosis is one major determinant for the occurrence and recurrence of ischemic stroke. MRI has been greatly improved over the past decade and proven to be useful in tissue classification and detection of thrombi in patients with high-risk carotid artery plaques. In our study, we evaluated the additional impact provided by T2* gradient echo imaging at ultra-high field MRI (9.4T) for the enhanced discrimination between plaque calcification, acute and old hemorrhage and the detection of intra-luminal thrombi.
High-Resolution MRI of Implanted Skin Chambers with
Michael Bock1, Eva Christina Wönne1, Fabian Kiessling1, Wolfhard Semmler1, Reiner Umathum1
1Deutsches Krebsforschungszentrum (dkfz), Heidelberg, Germany
The interaction of different cell types with tissue can be studied in a living animal with the help of a skin chamber that is surgically implanted under the skin. In this work two types of inductively coupled coils were integrated into skin chambers to enhance the signal from the interior of the chamber. MR images with isotropic 100 μm resolution have been acquired in mice at 1.5T and 3T in less than 10 min, which clearly show the neovasculature induced by tumor cells in the chamber.
Evaluation and Correction of Noise and
Resolution Induced Errors in Quantitative Trabecular Bone μMRI
Charles Qingchuan Li1, Jeremy F. Magland1, Chamith S. Rajapakse1, X Edward Guo2, Xiaohui Henry Zhang2, Felix W. Wehrli1
1University of Pennsylvania, Philadelphia, Pennsylvania, USA; 2Columbia University, New York City, New York, USA
Magnetic resonance micro-imaging (μMRI), in conjunction with digital image processing techniques, has been shown to be capable of non-invasively imaging trabecular bone and assessing structural changes caused by osteodegenerative disease. This work evaluated the effects of image noise and resolution on the accuracy of the derived structural parameters, and explored potential methods for correcting such errors. By simulating μMR images with controlled levels of noise and resolution, structural parameter calculations were shown to be skewed in a systematic but correctable manner.
A Closer Look Into "DESIRE" for NMR Microscopy
Markus Weiger1, Michael Fey1
1Bruker BioSpin AG, Faellanden, Switzerland
An extensive analysis of the alternative NMR microscopy technique DESIRE is presented. Simulations and experiments are used to investigate the aspects of signal enhancement, true spatial resolution, and contrast in structured objects.
Investigating Spatial Variances in MR Using Molecular
Information from MALDI Imaging Mass Spectrometry
Tuhin Kumar Sinha1, Zhengyu Yang1, William Michael Hardesty1, John C. Gore1
1Vanderbilt University, Nashville, USA
We demonstrate a method to investigate the systematic spatial variances found in MR images using MALDI imaging mass spectrometry. Using this technique we are able to correlate the observed MR relaxation phenomena with the underlying tissue composition. This research is aimed at determining which factors in tissue govern the contrast in MR imaging.
Fully-Integrated MR–Optical Imaging Concept for
Joerg Peter1, Reiner Umathum1, Katharina Schneider1, Gregor Schlosser1, Matthias Korn1, Michael Bock1, Wolfhard Semmler1
1German Cancer Research Center, Heidelberg, GermanyWe propose a method and apparatus for integrated optical and magnetic resonance imaging of in vivo distributions of fluorescent or bioluminescent probes and simultaneous detection of nuclear magnetic resonance signals in small objects, e.g. in mice. The method is based on an MRI-compatible light detector in which a photon sensor is placed at the focal plane of a microlens array. The apparatus has been validated by means of experimental phantom studies. Its preclinical use is proposed for solving problems connected to separately imaging optical and NMR signals, as for instance direct study and comparison of tracer/marker kinetics.