ISMRM 23rd Annual Meeting & Exhibition • 30 May - 05 June 2015 • Toronto, Ontario, Canada

Scientific Session • Magnetization Transfer

Friday 5 June 2015

Room 701 B

08:00 - 10:00


David C. Alsop, Ph.D., T.B.A.

08:00 0993.   
Application of a dipolar model to inhomogeneous magnetization transfer (ihMT)
Gopal Varma1, Olivier M Girard2, Valentin Prévost2, Aaron K Grant1, Guillaume Duhamel2, and David C Alsop1
1Radiology, Division of MR Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States, 2CRMBM UMR 7339, CNRS and Aix-Marseille Université, Marseille, France
The inhomogeneous magnetization transfer technique (ihMT) has gained attention for producing myelin selective images, but a model for its mechanism has not been established. This work develops a model based on existing applications of the Redfield-Provotorov theory to regular MT that predicted a dipolar order. The results from model fitting to mouse and human data provide measurable values for a relaxation time of the dipolar order, TD, consistent with the observable ihMT signal. The variation observed in TD between different regions of interest might provide further insight into the selectivity and/or optimization of the ihMT technique.

08:12 0994.   Towards a quantitative theory for inhomogeneous magnetization transfer
Scott D. Swanson1, Dariya I. Malyarenko2, and Mario L. Fabiilli2
1Department of Radiology, University of Michigan, Ann Arbor, Michigan, United States, 2Department of Radiology, University of Michigan, Michigan, United States

ihMT theory

08:24 0995.   
Further Evidence of an Orientation Dependence of Magnetization Transfer Parameters from Investigations in Post-Mortem Marmoset Brain
Henrik Marschner1, Riccardo Metere1, Stefan Geyer1, André Pampel1, and Harald E. Möller1
1Nuclear Magnetic Resonance, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Sachsen, Germany

We examine the apparent dependence of qMT parameters, in particular those of the T2b relaxation time of bound protons, on the white matter fiber orientation in a Post-Mortem Marmoset Brain. The observed angular dependence in the post-mortem data for highly ordered WM supports the hypothesis of orientation dependence of the RF absorption lineshape that was observed in human brain in vivo. Here, variation of the orientation is achieved by rotating the sample in the magnetic field.

08:36 0996.   Exploring a Flexible Pulse Design for Studying Magnetization Transfer
Peter van Gelderen1, Xu Jiang1, and Jeff H Duyn1
1AMRI, LFMI, NINDS, National Institutes of Health, Bethesda, MD, United States

Magnetization Transfer (MT) contrast is sensitive to brain myelination but lacks specificity, while quantification is difficult and requires lengthy experiments, including T1 measurement. Pulsed MT experiments may offer a simpler way to obtained quantitative measures, such as bound pool fraction and transfer rates. Here we explore a variation on a binominal pulse design for optimizing the pulsed MT experiment and demonstrate its application to study MT contrast in white matter.

08:48 0997.   Contrast Generation with a Novel Adiabatic On-Resonance Magnetization Transfer Preparation (MT-Prep)
Wolfgang G Rehwald1, David C Wendell2, Elizabeth R Jenista2, Han W Kim2, Enn-Ling Chen2, Igor Klem2, and Raymond J Kim2
1Siemens Healthcare, Durham, NC, United States, 2Cardiology, Duke University Medical School, Durham, North Carolina, United States

Magnetization transfer contrast could be a clinically and technically advantageous alternative to T2-contrast. It would be useful for imaging edema and creating tissue-blood contrast, if its energy and power requirements did not exceed the capabilities of most clinical MRI scanners. To address this issue, we designed an efficient adiabatic on-resonance MT module that imparts significant MT-weighting while remaining within the energy and power constraints of most clinical MRI scanners. In ten cardiac patients, we compared this module to standard high-power off-resonance MT preparation and established its image quality and contrast equivalence while only requiring a fraction of its energy.

09:00 0998.   
Study of Bound Proton T2 and Magnetization Transfer using Pulsed MT
Xu Jiang1,2, Peter van Gelderen1, Xiaozhen Li1, Emily Leibovitch3, Pascal Sati4, Afonso C. Silva5, and Jeff H Duyn1
1AMRI, LFMI, NINDS, NIH, Bethesda, MD, United States, 2Department of Physics, University of Maryland, College Park, MD, United States, 3Viral Immunology Section, Neuroimmunology Branch, NINDS, NIH, Bethesda, MD, United States, 4Translational Neuroradiology Unit, NINDS, NIH, Bethesda, MD, United States, 5CMU, LFMI, NINDS, NIH, Bethesda, MD, United States

Accurate knowledge of the T2 of bound (non-water) protons is very essential for optimization and quantification of MT contrast. Using optimized, 2ms long binomial MT pulses with varying amplitudes, and studying delay-dependent saturation of mobile water protons, we determined bound proton T2 to average 27μs, 17.5μs and 13.5μs in white matter, grey matter, and muscle tissue in marmoset in vivo, while the exchange rates between water and non-water protons were 13s-1, 30s-1, and 47s-1 respectively. The pulse-delay approach followed here proved a sensitive way to study MT contrast and is applicable to study of human brain at high field.

09:12 0999.   A new MT signal at -1.6 ppm via NOE-mediated saturation transfer
Xiao-Yong Zhang1, Hua Li1, Junzhong Xu1, Jingping Xie1, John C. Gore1, and Zhongliang Zu1
1Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States

Magnetization transfer (MT) provides a unique mechanism for producing contrast and makes MRI sensitive to the presence of metabolites, mobile macromolecules, and semisolid macromolecules through their ‘magnetic coupling’ effects on the water signal. Although the nuclear Overhauser enhancement (NOE)-mediated MT signal at -3.5 ppm has been recently studied, to date no in vivo MT effect at -1.6 ppm has been reported. We report a new MT signal MT at -1.6 ppm, which may reflect the NOE effect between choline headgroup of membrane phospholipids and water protons. The MT signal at -1.6 ppm could be used as a new biomarker in healthy rat brain.

09:24 1000.   
Oxidative stress sensitive magnetization transfer MRI of prostate cancer
Rongwen Tain1,2, Michael Abern3, Karen Xie1, X. Joe Zhou1,2, and Kejia Cai1,2
1Radiology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States, 2Center for MR Research, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States, 3Urology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States

Reduction-oxidation (Redox) imbalance due to oxidative stress may occur in pathologies including cancer. Developing imaging biomarkers for oxidative stress is a key research area. Recently, we presented the first non-invasive MRI method for mapping the tissue redox state based on the endogenous Chemical Exchange Saturation Transfer (CEST) contrast. It is well known that magnetization transfer (MT) can occur via chemical exchange (CEST) and/or dipole-dipole interactions (Nuclear Overhauser Enhancement or NOE). This study on ex vivo egg white tissues and in vivo prostate cancers demonstrated that MT in the broad definition is sensitive to oxidative stress through animal models.

09:36 1001.   Assessment of Amide Proton Transfer and Nuclear Overhauser Effects using long RF Saturation at 3T in Clinical Brain Tumor Applications
Jochen Keupp1 and Osamu Togao2
1Philips Research, Hamburg, Germany, 2Clinical Radiology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan

MTRasym can be robustly and efficiently measured in clinical settings, including 3D acquisitions with large coverage in less than 5 minutes. On the other hand, MTRasym as a measure for APT signal levels, was previously reported to be biased by Nuclear Overhauser effects (NOE) at opposite frequency offsets. The influence of NOE effects may strongly depend on the main magnetic field (B0) and on saturation parameters. Most reported studies were performed at ultra-high B0greater than or equal to7T and typically employed short RF saturation (Tsat<1s) and low saturation field amplitudes (e.g. B1,rms=0.5 µT). In this study, a previously proposed APT protocol (Tsat=2s; B1,rms=2 µT) on 3.0T MRI systems is applied for human brain tumor cases and analyzed for NOE contributions using improved Z-spectral fitting methods. It was hypothesized, that there is only a small or negligible NOE contrast between NAWM and tumor tissue using long saturation pulses at 3T. The study results indicate that MTRasym in combination with a specific protocol at 3T could be used to assess APT signal levels in clinical applications without significant interference of NOE effects.

09:48 1002.   Amplifying ATP Magnetization Exchange Effects by Band Inversion Transfer: A 31P NMR Study in Human Skeletal Muscle at 7T
Jimin Ren1,2, Baolian Yang3, A. Dean Sherry1,4, and Craig R. Malloy1,5
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States, 2Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, United States, 3Philips Healthcare, Cleveland, Ohio, United States, 4Department of Chemistry, University of Texas at Dallas, Richardson, Texas, United States, 5VA North Texas Health Care System, Dallas, Texas, United States

31P magnetization transfer studies in animals and humans suggest that transfer occurs not only between ATP and exchanging metabolites such as phosphocreatine and inorganic phosphate, but also among ATP spins. The latter effect, although small, is most consistent with 31P-31P NOE. Here, we explore a strategy to amplify this exchange effect within ATP by using a wideband inversion. A four-fold increase in lower case Greek beta-ATP signal reduction was observed by simultaneously inverting Pi, PCr, lower case Greek alpha- and lower case Greek gamma-ATP using an adiabatic pulse, as compared to by conventional frequency-selective inversion of only lower case Greek gamma-ATP. This observation is not consistent with known chemical exchange pathways.