SUTD Engineering Product Development (EPD) & SUTD-MIT International Design Center Distinguished Lecture (IEEE Singapore Section co-sponsored), New directions for brain MRI hardware and acquisition, by Professor Lawrence Wald (Harvard Medical School, MGH)



The possibility of studying the living human body with resolution, sensitivity and speed considerably above that provided by conventional MRI gradient encoding offers the potential to bring new levels of biology under the lens of non-invasive imaging. Although most academic MRI work focuses on acquisition and image reconstruction software, the scanner hardware ultimately limits the capabilities of the technology, and steady progress over the last 2 decades has shown that improvements are possible. This talk will discuss our work and others toward improving the detection and encoding technology of MRI.

Encoding, the ability to spatially localize physical information into an image is traditionally done with the Fourier encoding performed by application of switching, linear B0 field gradients. In the last 15 years, however, more and more of the spatial encoding is derived from the detector array, who’s spatial encoding ability is elegantly integrated with gradient encoding in parallel imaging methodology. Our goal is to find the logical limits of this combination and work to both increase the information content in the arrays (bigger arrays), and introduce schemes which improve the time-efficiency of MR encoding with little penalty in sensitivity. Recently, this has lead to a nearly 10 fold speed up of the functional MRI acquisition.

Increasing the spatial resolution of functional imaging to the columnar and laminar level has also started to be routinely demonstrated, but remains fundamentally encoding limited. To address this we have pushed highly parallel detection at high field and are currently working to improve the B0 shim at 7T. Since poor B0 homogeneity at ultra high field (7T) limits the time available for gradient encoding (to < T2*), we develop a new, high-order matrix shimming approach at 3T and 7T. For MR diffusion imaging, the applied diffusion gradients encode the diffusion of water on a microscopic scale. For this application we introduce specialized/stronger gradients designed to perform this more efficiently on a scanner designed around diffusion imaging for the Human Connectome Project.

Finally, we note that the weight, power and cooling requirements of gradient coils as well as the magnet size/weight are barriers to using MRI in many locations such as an ambulance or rural health clinics as well as point-of-care situations, such as surgical recovery rooms. We have therefore developed a portable brain MRI system (<100kg) which does not use traditional gradient coils at all, but encodes brain images by rotating an inhomogeneous magnet around the patient’s head.

Bio-sketch of the lecturer:

Lawrence L. Wald, Ph.D., Received a Ph.D. in Physics from the University of California at Berkeley in 1992 with a thesis related to optical detection of NMR under the direction of Prof. Erwin Hahn. He obtained further (postdoctoral) training in condensed matter physics at

Berkeley and then in radiology/MRI at the University of California at San Francisco where he worked on MR spectroscopic imaging of brain tumors and the development of phased array coils for high resolution imaging and spectroscopy with Profs. Vigneron and Nelson. He began his academic career as an Instructor at the Harvard Medical School in the Brain Imaging Center of McLean Hospital and since 1998 at the Massachusetts General Hospital Dept. of Radiology in the NMR Center (now the A.A. Martinos Center for Biomedical Imaging.) He is currently an Associate Professor of Radiology at the Harvard Medical School and affiliated faculty in the Harvard MIT HST program and a visiting Assoc. Prof. of EECS at MIT (2012, 2013). At the Martinos Center he is Director of the MGH Imaging Core Facility.

He is a member of the College of Fellows of the American Institute of Medical and Biological Engineers (AIMBE) and a Fellow and former Board member of the International Society of Magnetic Resonance in Medicine (ISMRM). He is an author on approximately 150 publications, 10 patents and enjoys an active role in educational programs at MGH and MIT and through the ISMRM and Radiological Society of North America (RSNA).

His group at MGH works on hardware and software methods development for improved MRI of the living human brain. Some of the current and recent projects include i) the development of highly parallel receive array coils for high field imaging, ii) the development of parallel imaging methods employing controlled aliasing for improved Simultaneous MultiSlice (SMS) and 3D imaging, iii) Ultra-high field (7T) methods for high resolution fMRI, parallel transmit pulse design and hardware for reduced SAR imaging at 3T and 7T, iv) high gradient strength diffusion imaging for the Human Connectome Project, v) the development of a portable low field MRI systems using rotating B0 encoding.

  • Venue was changed to "Lecture Theater 4, Singapore University of Technology and Design, Singapore 138682". Orig#55986 2014-10-17 15:57:02
Mon Oct 20, 2014
2:00 PM - 3:30 PM SGT
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