Magnetization Transfer

Monday 12 May 2014

Richard D. Dortch^1,2, Lindsey M. Dethrage², Ke Li^1,2, Bruce M. Damon^1,2, John C. Gore^1,2, and Seth A. Smith^1,2
1Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, ²Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States

Previous work has demonstrated that the macromolecular-to-free proton pool size ratio (PSR) is related to myelin content; yet, no studies have reportedPSR mapping in peripheral nerves in vivo. This can be attributed to the challenges of quantitative magnetization transfer (qMT) imaging in nerve, including the influence of fat and the need for higher resolution. The goal of this work was to develop qMT approaches for the currently inaccessible (via electrophysiology) sciatic nerves of healthy controls as a baseline for future studies in neuropathy patients. Our findings demonstrate that PSR can be robustly measured in the sciatic nerve in vivo.

Rebecca Sara Samson¹, Manuel Jorge Cardoso^2,3, Nils Muhlert¹, Varun Sethi¹, Maria A Ron¹, Sebastian Ourselin^2,3, David H Miller¹, Declan T Chard¹, and Claudia A M Wheeler-Kingshott^1
1NMR Research Unit, Department of Neuroinflammation, Queen Square MS Centre, UCL Institute of Neurology, London, United Kingdom, ²Centre for Medical Image Computing, UCL Department of Computer Sciences, UCL, London, United Kingdom, ³Dementia Research Centre, Department of Neurodegenerative Diseases, UCL Institute of Neurology, London, United Kingdom

A previous study suggests that outer cortical magnetization transfer ratio (MTR) has the potential to be a sensitive measure of pathology that is linked to clinical disease progression in relapse-onset multiple sclerosis. However, to determine the utility of the inner and outer cortical MTR measurement method it is important to determine the reproducibility of the technique. Here we demonstrate that inner and outer cortical MTR have coefficients of variation of 1.23% and 0.99% respectively.

James H Holmes¹, Alexey Samsonov², Patrick A Turski², Aaron S Field², and Kevin M Johnson^3
1Global MR Applications and Workflow, GE Healthcare, Madison, WI, United States, ²Radiology, University of Wisconsin-Madison, Madison, WI, United States, ³Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

We demonstrate the combination of a magnetization transfer (MT) preparation pulse and a zero TE (ZTE) imaging data acquisition. This work shows the potential for a MR ratio (MTR) imaging of white mater disease using an intermittent MT preparation pulse to reduce SAR and scan time. The ZTE acquisition enables visualization of short T2 species while providing the benefit of low acoustic noise to improve patient comfort.

Shaolin Yang^1,2, Olusola Ajilore¹, Minjie Wu¹, Melissa Lamar¹, and Anand Kumar^1
1Department of Psychiatry, University of Illinois at Chicago, Chicago, IL, United States, ²Department of Radiology, University of Illinois at Chicago, Chicago, IL, United States

A cross-sectional study using magnetization transfer ratio (MTR) imaging was performed to examine the biophysical integrity of macromolecular protein pools in gray matter and white matter of the fronto-striato-thalamic circuits in patients with type 2 diabetes mellitus (T2DM) and comparison controls to determine the impacts of T2DM on the abnormalities of human brain. Compared with non-diabetic controls, T2DM patients had significantly lower MTR in dorsal anterior cingulate cortex (ACC) and head of caudate nucleus (hCaud), also with a tendency to significance in rostral ACC. The compromised MTRs were correlated with T2DM-related clinical measures and neuropsychological performance in distinct domains.

Lukas Pirpamer¹, Florian Franz Erich Borsodi¹, Gernot Reishofer², Christian Langkammer¹, Reinhold Schmidt¹, and Stefan Ropele^1
1Department of Neurology, Medical University of Graz, Graz, Austria, ²Department of Radiology, Medical University of Graz, Graz, Austria

The bound pool fraction (BPF) is a fundamental parameter for magnetization transfer and therefore expected to be more sensitive for age-related tissue changes compared to the conventional MTR. This study investigated the change of the BPF in several white-matter regions assessed over age in a normal aging cohort. This study confirms the higher sensitivity of the BPF in particular for WM regions that are susceptible for developing age related white matter hyperintensities.

Pouria Mossahebi¹, Andrew L Alexander^2,3, Aaron S Field^1,4, and Alexey A Samsonov^4
1Biomedical Engineering, University of Wisconsin, Madison, WI, United States, ²Medical Physics, University of Wisconsin, Madison, WI, United States,³Waisman Lab for Brain Imaging and Behavior, University of Wisconsin, Madison, WI, United States, ⁴Radiology, University of Wisconsin, Madison, WI, United States

Gray matter demyelination has recently been recognized as an important pathological substrate of MS disease. MT imaging approaches has demonstrated high sensitivity to myelination in white matter. Its applications to cortical GM characterization, however, we have to take into account additional factors related to anatomical organization of cortical GM such as partial volume effect (PVE) with CSF. We have proposed a qMT imaging (NE-mCRI) approach that allows isolating a non-exchanging (NE) voxel compartment with distinct relaxation properties such as CSF. In this work, we analyze the effect of NE component on MTR and mCRI parameters and provide results of numerical, phantom and in-vivo validation of the approach as a way to minimize underestimation of qMT measures due to PVE. Additionally, we developed a fast-optimized protocol for in-vivo application of NE-mCRI.

Henrik Marschner¹, André Pampel¹, Roland Müller¹, Nicholas A. Bock², Marcel Weiss^1,3, Stefan Geyer¹, and Harald E. Möller^1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany, ²McMaster University, Ontario, Canada, ³University of Amsterdam, North Holland, Netherlands

We present results of quantitative magnetization transfer imaging (qMTI) in high resolution for quantification of (qMT) parameters of otherwise MR-invisible macromolecules. qMTI was performed on a post-mortem marmoset brain at 3T and the results are compared to T1 mapping results obtained at 7T. The high resolution of 200 µm permits visualization of cortical substructures in the marmoset brain, as presented for the stria of Gennari. An analysis of correlation between the macromolecular pool-size fraction and T1 shows different linear regressions in white and gray matter. This suggests i) different myelination contribution in both contrast parameters, or ii) other contributing factors.

Guillaume Duhamel¹, Valentin Prevost¹, Gopal Varma², David C Alsop², and Olivier Girard^1
1CRMBM, CNRS 7339, Aix-Marseille Université, Marseille, 13005, France, ²Radiology, Beth Israel Deaconess Med. Center, Harvard Medical School, Boston, MA, United States

A recent MT technique, referred as inhomogeneous MT (ihMT) and able to reveal the inhomogenous component of the MR spectrum has been proposed to specifically image the myelinated structures. Contribution of MT asymmetry effects in the ihMT signal is assessed in this study.

Junzhong Xu¹, Ke Li¹, Zhongliang Zu¹, Xia Li¹, Dainel F Gochberg¹, and John C Gore^1
1Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, United States

This study demonstrates the first implementation of quantitative MT imaging of cancer using selective inversion recovery. In addition, a new SIR-EPI sequence was developed to accelerate the acquisition but retain the fitting accuracy of qMT parameters. The results presented not only assist better understanding of the changes in the macromolecular contents of tumors, but also are important for quantifying other imaging contrasts such as chemical exchange saturation transfer (CEST) of tumors.

Laura Turati¹, Fulvio Baggi¹, Marco Moscatelli¹, Alfonso Mastropietro^2,3, Ileana Zucca², Alessandra Erbetta⁴, Chiara Cordiglieri¹, Greta Brenna¹, Nicholas Dowell⁵, Renato Mantegazza¹, Ludovico Minati^2,5, and Mara Cercignani^5,6
1Neuroimmunology and Neuromuscular Diseases Unit, Neurological Institute "Carlo Besta", Milan, Italy, ²Scientific Department, Neurological Institute "Carlo Besta", Milan, Italy, ³Department of Electronic, Information and Bioengineering, Politecnico of Milan, Milan, Italy, ⁴Neuroradiology Unit, Neurological Institute "Carlo Besta", Milan, Italy, ⁵CISC, Brighton and Sussex Medical School, Falmer, East Sussex, United Kingdom, ⁶Neuroimaging Laboratory, IRCCS Santa Lucia, Rome, Italy

This paper presents a validation of the macromolecular pool ratio (F) derived from quantitative magnetization transfer (MT) imaging as myelin marker. In contrast with previous work in this area, which focused on ex-vivo validation, we used a reversible model of demyelination, namely cuprizone-treated mice, to investigate changes in F in the corpus callosum during demyelination and remyelination in vivo. A strong linear relationship was found between F and histological markers of myelin, providing the first direct confirmation that F estimated from quantitative MT imaging performed in-vivo is a viable proxy of myelin.