Direct Control of the Temperature Rise in Parallel Transmission by Means of Temperature Virtual Observation Points: Simulations at 10.5 Tesla

Overview

Journal Magn Reson Med

Publisher Wiley

Specialty Radiology

Date 2015 Mar 11

PMID 25754685

Citations 14

Authors

Nicolas Boulant

Xiaoping Wu

Gregor Adriany

Sebastian Schmitter

Kamil Ugurbil

Pierre-Francois Van de Moortele

Affiliations

Soon will be listed here.

Abstract

Purpose: A method using parallel transmission to mitigate B1+ inhomogeneity while explicitly constraining the temperature rise is reported and compared with a more traditional SAR-constrained pulse design.

Methods: Finite difference time domain simulations are performed on a numerical human head model and for a 16-channel coil at 10.5 Tesla. Based on a set of presimulations, a virtual observation point compression model for the temperature rise is derived. This compact representation is then used in a nonlinear programming algorithm for pulse design under explicit temperature rise constraints.

Results: In the example of a time-of-flight sequence, radiofrequency pulse performance in some cases is increased by a factor of two compared with SAR-constrained pulses, while temperature rise is directly and efficiently controlled. Pulse performance can be gained by relaxing the SAR constraints, but at the expense of a loss of direct control on temperature.

Conclusion: Given the importance of accurate safety control at ultrahigh field and the lack of direct correspondence between SAR and temperature, this work motivates the need for thorough thermal studies in normal in vivo conditions. The tools presented here will possibly contribute to safer and more efficient MR exams.

Citing Articles

SAR and temperature distributions in a database of realistic human models for 7 T cardiac imaging.

Steensma B, Meliado E, Luijten P, Klomp D, van den Berg C, Raaijmakers A NMR Biomed. 2021; 34(7):e4525.

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Solving the Time- and Frequency-Multiplexed Problem of Constrained Radiofrequency Induced Hyperthermia.

Kuehne A, Oberacker E, Waiczies H, Niendorf T Cancers (Basel). 2020; 12(5).

PMID: 32344914 PMC: 7281622. DOI: 10.3390/cancers12051072.

Parallel Transmission for Ultrahigh Field MRI.

Deniz C Top Magn Reson Imaging. 2019; 28(3):159-171.

PMID: 31188274 PMC: 7039313. DOI: 10.1097/RMR.0000000000000204.

IMPULSE: A scalable algorithm for design of minimum specific absorption rate parallel transmit RF pulses.

Pendse M, Stara R, Khalighi M, Rutt B Magn Reson Med. 2018; 81(4):2808-2822.

PMID: 30426583 PMC: 6372346. DOI: 10.1002/mrm.27589.

Optimization of the order and spacing of sequences in an MRI exam to reduce the maximum temperature and thermal dose.

Carluccio G, Collins C Magn Reson Med. 2018; 81(3):2161-2166.

PMID: 30329177 PMC: 6927043. DOI: 10.1002/mrm.27503.

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