Direct SAR mapping by thermoacoustic imaging: A feasibility study.

TitleDirect SAR mapping by thermoacoustic imaging: A feasibility study.
Publication TypeJournal Article
Year of Publication2017
AuthorsWinkler SA, Picot PA, Thornton MM, Rutt BK
JournalMagn Reson Med
Volume78
Issue4
Pagination1599-1606
Date Published2017 10
ISSN1522-2594
KeywordsAbsorption, Physicochemical, Acoustics, Computer Simulation, Equipment Design, Feasibility Studies, Head, Hot Temperature, Humans, Magnetic Resonance Imaging, Models, Biological, Phantoms, 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 (r  = 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.

DOI10.1002/mrm.26517
Alternate JournalMagn Reson Med
PubMed ID27779779
PubMed Central IDPMC5405009
Grant ListK99 EB024341 / EB / NIBIB NIH HHS / United States
P41 EB015891 / EB / NIBIB NIH HHS / United States
R00 EB024341 / EB / NIBIB NIH HHS / United States
Related Institute: 
MRI Research Institute (MRIRI)

Weill Cornell Medicine
Department of Radiology
525 East 68th Street New York, NY 10065