High field MRI (3T, 7T and above) offers many potential advantages to clinical and scientific studies, including increased sensitivity and improved image contrast creating the potential for improved characterization of biological function and anatomy in health and disease. Parallel transmission (pTx) uses multiple excitation coils driven by independent RF pulse waveforms to subdivide the transmit field into multiple spatial regions each controlled by a separate transmit channel. Increasing the number of spatially distinct transmit elements and using temporally distinct RF pulse waveforms creates spatial degrees of freedom that allow the spatial pattern of the array to be exploited in the excitation process. Previous pTx work by ourselves and others has concentrated on the potential to utilize this additional flexibility to move beyond the uniform slice-select excitation. In the current proposal, we propose a program of translational bioengineering development to widely impact 3T clinical imaging and facilitate the advance of 7T clinical imaging by develop and validate novel methods to increase the degrees of freedom available in pTx pulse design together with novel optimization schemes which can convert these degrees of freedom into reduced SAR. Successful implementation of such methods potentially allow us to expand the quality of clinical imaging by providing more slices, higher flip angles, or shorter TR periods in a wide range of clinical protocols. Additionally we will develop methods which directly address the local SAR problems of the more exotic 2D and 3D spatially tailored pulses, which has proven to be a major limitation of these pulses. Finally we provide a theoretical and experimental validation of the SAR models in ubiquitous use.

Public Health Relevance

This bioengineering project seeks to develop translational technology to improve Magnetic Resonance Imaging (MRI). Its ultimate goal is to provide improve the MR images used for clinical diagnosis of disease and to increase the ability of MR as a scientific tool for studying anatomy and function within the living human body in health and disease.

National Institute of Health (NIH)
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Research Project (R01)
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Biomedical Imaging Technology Study Section (BMIT)
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Liu, Guoying
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Massachusetts General Hospital
United States
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Guérin, Bastien; Gebhardt, Matthias; Serano, Peter et al. (2015) Comparison of simulated parallel transmit body arrays at 3 T using excitation uniformity, global SAR, local SAR, and power efficiency metrics. Magn Reson Med 73:1137-50
Guérin, Bastien; Setsompop, Kawin; Ye, Huihui et al. (2015) Design of parallel transmission pulses for simultaneous multislice with explicit control for peak power and local specific absorption rate. Magn Reson Med 73:1946-53
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Graedel, Nadine N; Polimeni, Jonathan R; Guerin, Bastien et al. (2015) An anatomically realistic temperature phantom for radiofrequency heating measurements. Magn Reson Med 73:442-50
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Cauley, Stephen F; Polimeni, Jonathan R; Bhat, Himanshu et al. (2014) Interslice leakage artifact reduction technique for simultaneous multislice acquisitions. Magn Reson Med 72:93-102
Poser, Benedikt A; Anderson, Robert James; Guerin, Bastien et al. (2014) Simultaneous multislice excitation by parallel transmission. Magn Reson Med 71:1416-27
Chang, Wei-Tang; Setsompop, Kawin; Ahveninen, Jyrki et al. (2014) Improving the spatial resolution of magnetic resonance inverse imaging via the blipped-CAIPI acquisition scheme. Neuroimage 91:401-11
Fujimoto, Kyoko; Polimeni, Jonathan R; van der Kouwe, Andre J W et al. (2014) Quantitative comparison of cortical surface reconstructions from MP2RAGE and multi-echo MPRAGE data at 3 and 7 T. Neuroimage 90:60-73

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