Publication Type Academic Article
Authors Winkler S, Picot P, Thornton M, Rutt B
Journal Magn Reson Med
Volume 78
Issue 4
Pagination 1599-1606
Date Published 10/25/2016
ISSN 1522-2594
Keywords Acoustics, Magnetic Resonance Imaging
Abstract PURPOSE: To develop a new method capable of directly measuring specific absorption rate (SAR) deposited in tissue using the thermoacoustic signal induced by short radiofrequency (RF) pulse excitation. THEORY: A detailed model based on the thermoacoustic wave generation and propagation is presented. METHODS: We propose a new concept for direct measurement of SAR, to be used as a safety assessment/monitoring tool for MRI. The concept involves the use of short bursts of RF energy and the measurement of the resulting thermoacoustic excitation pattern by an array of ultrasound transducers, followed by image reconstruction to yield the 3D SAR distribution. We developed a simulation framework to model this thermoacoustic SAR mapping concept and verified the concept in vitro. RESULTS: Simulations show good agreement between reconstructed and original SAR distributions with an error of 4.2, 7.2, and 8.4% of the mean SAR values in axial, sagittal, and coronal planes and support the feasibility of direct experimental mapping of SAR distributions in vivo. The in vitro experiments show good agreement with theory (r2 = 0.52). CONCLUSIONS: A novel thermoacoustic method for in vivo mapping of local SAR patterns in MRI has been proposed and verified in simulation and in a phantom experiment. Magn Reson Med 78:1599-1606, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
DOI 10.1002/mrm.26517
PubMed ID 27779779
PubMed Central ID PMC5405009
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