ISMRM 24th Annual Meeting & Exhibition • 07-13 May 2016 • Singapore

Scientific Session: Diffusion Validation Using Phantoms & Histology

Thursday, May 12, 2016
Room 324-326
13:30 - 15:30
Moderators: Matthew Budde, Hao Huang

Intravoxel Incoherent Motion MRI in a 3-Dimensional Microvascular Flow Phantom
Moritz Schneider1, Thomas Gaaß1,2, Julien Dinkel1,2, Michael Ingrisch1, Maximilian F Reiser1, and Olaf Dietrich1
1Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Munich, Germany, 2Comprehensive Pneumology Center, German Center for Lung Research, Munich, Germany
In this study we present intravoxel incoherent motion (IVIM) measurements in a flow phantom consisting of a 3-dimensional capillary network made from melt-spun, sacrificial sugar structures embedded in a synthetic resin. IVIM parameters were determined at varying water flow rates. The pseudodiffusion D* (associated with flow velocity) as well as the product D*×f (which constitutes a measure of flow) show proportionality to the applied flow rates. These results demonstrate that the presented flow phantom is ideal to assess the applicability of IVIM measurements and influence factors such as flow rates, capillary diameter or acquisition parameters.

Single MR spectral peak diffusion phantom with wide ADC range based on acetone, H2O and manganese chloride
Xiaoke Wang1, Scott B Reeder1,2,3,4,5, and Diego Hernando2
1Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States, 2Radiology, University of Wisconsin-Madison, Madison, WI, United States, 3Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, 4Medicine, University of Wisconsin-Madison, Madison, WI, United States, 5Emergency Medicine, University of Wisconsin-Madison, Madison, WI, United States
Practical diffusion phantoms are urgently needed for technique development, protocol harmonization and quality assurance of quantitative diffusion MRI. Ideally, a diffusion phantom should have a single-peak NMR spectrum, Gaussian diffusion, with a wide range of tunable apparent diffusion coefficients (ADC). In this work, we developed and validated a novel diffusion phantom based on acetone-water mixtures doped with MnCl2. This phantom exhibits the desired signal behavior, where water modulates the ADC of acetone, and MnCl2 both eliminates water signal (through T2 shortening) and shortens the T1 of acetone. 

Validation of Diffusion Tensor MRI with Structure Tensor Synchrotron Imaging
Irvin Teh1, Darryl McClymont1, Marie-Christine Zdora2,3, Valentina Davidoiu4, Hannah J Whittington1, Christoph Rau2, Irene Zanette2, and Jürgen E Schneider1
1Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom, 2Diamond Light Source, Didcot, United Kingdom, 3Department of Physics and Astronomy, University College London, London, United Kingdom, 4Department of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom
Diffusion tensor imaging (DTI) is widely used to assess tissue microstructure, but is limited in resolution and cannot resolve multiple fibre populations within a voxel. Existing methods for validating DTI are limited in either resolution or coverage. 2D histological methods are additionally destructive and prone to tissue distortion. In contrast, synchrotron imaging strikes an excellent balance between resolution and coverage. Here, we demonstrate for the first time, the prospect of validating DTI with structure tensor analysis of synchrotron imaging data. Tensors reconstructed with DTI and structure tensor synchrotron imaging were consistent across the left ventricular wall of the heart.

Neuroplasticity changes in rat brain following targeted irradiation assessed by diffusion MRI tractography validated by histology and behavioral tests - Permission Withheld
Julie Constanzo1, Matthieu Dumont2, Luc Tremblay1, Philippe Sarret3, Jean-Michel Longpré3, Karyn Kirby3, Sameh Geha4, Laurence Masson-Côté1, Benoit Paquette1, and Maxime Descoteaux2
1Nuclear Medicine and Radiobiology, Sherbrooke University, Sherbrooke, QC, Canada, 2Computing Science, Sherbrooke University, Sherbrooke, QC, Canada, 3Pharmacology and biophysics, Sherbrooke University, Sherbrooke, QC, Canada, 4Pathology, Sherbrooke University, Sherbrooke, QC, Canada
Despite its high efficiency for treating brain tumors and metastases, stereotactic radiosurgery (SRS) may lead to brain swelling, necrosis, and neuronal dysfunction, thus inducing delayed adverse effects such as cognitive decline and stroke-like symptoms. Altogether, our results revealed that SRS treatment induces region-specific plasticity (i.e. structural and function changes), as demonstrated by neuronal matrix remodeling using diffusion MRI and appropriate HARDI reconstruction, corresponding to histopathological modifications and changes in behavioral responses.

Comparing Diffusion MRI with the Fiber Architecture and Tract Density of Gyral Blades
Kurt Schilling1, Vaibhav Janve1, Yurui Gao1, Iwona Stepniewska1, Bennett Landman1, and Adam Anderson1
1Vanderbilt University, Nashville, TN, United States
It has been reported that diffusion tractography has a tendency for streamlines to terminate preferentially on gyral crowns rather than on sulcal walls or fundi. Rather than anatomical reality, it has been suggested that this is a bias associated with tractography. To better understand this issue, we compare histology to diffusion MRI of the same specimen. We measure the trajectories and density of axons crossing the gray matter/white matter boundary and compare to diffusion tensor measures and deterministic tractography. The results of this study lead to a better understanding of gyral anatomy and potential limitations of fiber tractography.

Post-mortem inference of the inner connectivity of the human hippocampus using ultra-high field diffusion MRI at 11.7T
Justine Beaujoin1,2,3, Fawzi Boumezbeur1,2,3, Jérémy Bernard1,2,3, Markus Axer4, Jean-François Mangin2,3,5,6, and Cyril Poupon1,2,3,6
1CEA NeuroSpin / UNIRS, Gif-sur-Yvette, France, 2Université Paris-Saclay, Orsay, France, 3FLI / Noeud Paris-Sud, Orsay, France, 4Forschungszentrum Jülich, INM1, Jülich, Germany, 5CEA NeuroSpin / UNATI, Gif-sur-Yvette, France, 6, Gif-sur-Yvette, France
In this work, we demonstrate that post-mortem ultra-high field (11.7T) / ultra-high gradients (760mT/m) diffusion-weighted MRI allows to finely map the inner connectivity of the human hippocampus and we show that the polysynaptic intra-hippocampal pathway can be accurately reconstructed using fiber tractography techniques at very high spatial/angular resolutions.

Post-mortem diffusion MRI of cervical spine and nerves roots
Wieke Haakma1,2,3, Lidy Kuster2, Martijn Froeling1, Lars Uhrenholt2, Michael Pedersen3,4, Jeroen Hendrikse1, Alexander Leemans5, and Lene Warner Thorup Boel2
1Radiology, University Medical Center Utrecht, Utrecht, Netherlands, 2Forensic Medicine, Aarhus University, Aarhus, Denmark, 3Comparative Medicine Lab, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark, 4MR Research Center, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark, 5Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands
In this work we examined the architecture and diffusion measures of the cervical spine and nerves in non-fixated post-mortem subjects. We were able to display the architectural configuration of the cervical nerves at the level of C4-C8 and we computed reference values for the diffusion measures in these nerves. We showed with great detail the ventral and dorsal nerve roots with fiber tractography. Microscopic examination revealed normal anatomy. We expect that post-mortem diffusion MRI will be valuable for understanding of pathological mechanisms underlying degenerative neurological diseases, as it is possible to compare any findings directly to histological examinations. 

Microstructure models for diffusion MRI in breast cancer and surrounding stroma: an ex vivo study
Colleen Bailey1, Bernard Siow2, Eleftheria Panagiotaki1, John H Hipwell1, Sarah E Pinder3, Daniel C Alexander1, and David J Hawkes1
1Centre for Medical Image Computing, University College London, London, United Kingdom, 2Centre for Advanced Biomedical Imaging, University College London, London, United Kingdom, 3Breast Research Pathology, King's College London and Guy's Hospital, London, United Kingdom
A variety of one- and two-compartment models were fitted to rich diffusion data sets from ex vivo breast tissue samples containing tumour. Two compartment models with restriction explained the data better than conventional ADC and bi-exponential models, as determined by the Akaike Information Criterion. In four of seven samples, anisotropy was also observed, although parametric maps of the primary eigenvector direction show that regions of coherence are small (~1 mm diameter).

Validation of quantitative MRI metrics using full slice histology with automatic axon segmentation
Tanguy Duval1, Blanche Perraud1, Manh-Tung Vuong1, Nibardo Lopez Rios1,2, Nikola Stikov1,3, and Julien Cohen-Adad1,4
1Polytechnique Montréal, Montréal, QC, Canada, 2Medical Biophysics Center, Oriente University, Santiago de Cuba, Cuba, 3Montreal Heart Institute, Montréal, QC, Canada, 4Functional Neuroimaging Unit, CRIUGM, Université de Montréal, Montréal, QC, Canada
In this work we propose to validate and compare AxCaliber/ActiveAx/Noddi/MTV in the spinal cord using full slice histology with axon/myelin segmentation. High resolution data (150µm/px) were acquired on an ex vivo spinal cord and compared voxel by voxel with histology. We found that q-space metrics were precise enough to distinguish between various fiber distributions. A correlation coefficient of r=0.62 was found between AxCaliber and histology for axon diameter metric. Also, good agreement were found between the different q-space models and with MTV.

Validating tractography of high resolution post-mortem human brain at 7T with polarized light imaging
Sean Foxley1, Jeroen Mollink1, Saad Jbabdi1, Stuart Clare1, Moises Hernandez Fernandez1, Connor Scott2, Olaf Ansorge2, and Karla Miller1
1FMRIB Centre, University of Oxford, Oxford, United Kingdom, 2Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
In this work we present voxel-wise orientation estimates from diffusion-weighted steady state free precession MRI data of post-mortem human brain, acquired with three resolutions at 7T. Data were acquired with 0.5mm, 1mm, and 2mm isotropic resolution over 90 directions. These resolutions were chosen because 1mm and 2mm are typical of in vivo DTI. Deterministic tractography was produced in various regions using the highest resolution dataset. Orientation maps demonstrate small structures that are less apparent in lower resolution data. Orientation estimates and tractography results were validated with polarized light microscopy imaging.

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