Direct control of the temperature rise in parallel transmission by means of temperature virtual observation points: Simulations at 10.5 tesla

Research output: Contribution to journalArticle

18 Citations (Scopus)

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.

Original languageEnglish (US)
Pages (from-to)249-256
Number of pages8
JournalMagnetic resonance in medicine
Volume75
Issue number1
DOIs
StatePublished - Jan 1 2016

Fingerprint

Observation
Temperature
Hot Temperature
Head
Safety

Keywords

  • optimization
  • parallel transmission
  • temperature
  • ultrahigh field
  • virtual observation points

Cite this

@article{884e3454d1564d6d98e3d1e308faccce,
title = "Direct control of the temperature rise in parallel transmission by means of temperature virtual observation points: Simulations at 10.5 tesla",
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.",
keywords = "optimization, parallel transmission, temperature, ultrahigh field, virtual observation points",
author = "Nicolas Boulant and Xiaoping Wu and Gregor Adriany and Sebastian Schmitter and Kamil Uğurbil and {Van de Moortele}, {Pierre Fran{\cc}ois}",
year = "2016",
month = "1",
day = "1",
doi = "10.1002/mrm.25637",
language = "English (US)",
volume = "75",
pages = "249--256",
journal = "Magnetic Resonance in Medicine",
issn = "0740-3194",
publisher = "John Wiley and Sons Inc.",
number = "1",

}

TY - JOUR

T1 - Direct control of the temperature rise in parallel transmission by means of temperature virtual observation points

T2 - Simulations at 10.5 tesla

AU - Boulant, Nicolas

AU - Wu, Xiaoping

AU - Adriany, Gregor

AU - Schmitter, Sebastian

AU - Uğurbil, Kamil

AU - Van de Moortele, Pierre François

PY - 2016/1/1

Y1 - 2016/1/1

N2 - 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.

AB - 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.

KW - optimization

KW - parallel transmission

KW - temperature

KW - ultrahigh field

KW - virtual observation points

UR - http://www.scopus.com/inward/record.url?scp=84924179895&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84924179895&partnerID=8YFLogxK

U2 - 10.1002/mrm.25637

DO - 10.1002/mrm.25637

M3 - Article

C2 - 25754685

AN - SCOPUS:84924179895

VL - 75

SP - 249

EP - 256

JO - Magnetic Resonance in Medicine

JF - Magnetic Resonance in Medicine

SN - 0740-3194

IS - 1

ER -