Local specific absorption rate in brain tumors at 7 tesla

Purpose MR safety at 7 Tesla relies on accurate numerical simulations of transmit electromagnetic fields to fully assess local specific absorption rate (SAR) safety. Numerical simulations for SAR safety are currently performed using models of healthy patients. These simulations might not be useful f...

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Bibliographic Details
Published in:Magnetic resonance in medicine 2016-01, Vol.75 (1), p.381-389
Main Authors: Restivo, Matthew C., van den Berg, Cornelis A.T., van Lier, Astrid L.H.M.W., Polders, Daniël L., Raaijmakers, Alexander J.E., Luijten, Peter R., Hoogduin, Hans
Format: Article
Language:English
Subjects:
7 Tesla
Absorption
Absorption, Radiation
Brain
Brain - pathology
Brain - physiopathology
Brain cancer
Brain Neoplasms - pathology
Brain Neoplasms - physiopathology
Brain tumors
Computer Simulation
conductivity
Dielectric properties
Electric Impedance
Electrical properties
Electromagnetic fields
Estimation
Humans
Lesions
Mathematical models
Models, Biological
Patient-Specific Modeling
Patients
Radio Waves
Radiometry - methods
Reproducibility of Results
RF heating
Safety
SAR
Sensitivity and Specificity
simulation
Tomography
Tumors
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Summary:Purpose MR safety at 7 Tesla relies on accurate numerical simulations of transmit electromagnetic fields to fully assess local specific absorption rate (SAR) safety. Numerical simulations for SAR safety are currently performed using models of healthy patients. These simulations might not be useful for estimating SAR in patients who have large lesions with potentially abnormal dielectric properties, e.g., brain tumors. Theory and Methods In this study, brain tumor patient models are constructed based on scans of four patients with high grade brain tumors. Dielectric properties for the modeled tumors are assigned based on electrical properties tomography data for the same patients. Simulations were performed to determine SAR. Results Local SAR increases in the tumors by as much as 30%. However, the location of the maximum 10‐gram averaged SAR typically occurs outside of the tumor, and thus does not increase. In the worst case, if the tumor model is moved to the location of maximum electric field intensity, then we do observe an increase in the estimated peak 10‐gram SAR directly related to the tumor. Conclusion Peak local SAR estimation made on the results of a healthy patient model simulation may underestimate the true peak local SAR in a brain tumor patient. Magn Reson Med 75:381–389, 2016. © 2015 Wiley Periodicals, Inc.
ISSN:0740-3194
1522-2594
DOI:10.1002/mrm.25653