• Frank F J Simonis, Esben T Petersen, Lambertus W Bartels, Jan J W Lagendijk, and Cornelis A T van den Berg.
• Department of Radiotherapy, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands.
• Magn Reson Med. 2015 Mar 1; 73 (3): 1184-9.

PurposeMR thermometry (MRT) is a noninvasive method for measuring temperature that can potentially be used for radio frequency (RF) safety monitoring. This application requires measuring absolute temperature. In this study, a multigradient-echo (mGE) MRT sequence was used for that purpose. A drawback of this sequence, however, is that its accuracy is affected by background gradients. In this article, we present a method to minimize this effect and to improve absolute temperature measurements using MRI.TheoryBy determining background gradients using a B0 map or by combining data acquired with two opposing readout directions, the error can be removed in a homogenous phantom, thus improving temperature maps.MethodsAll scans were performed on a 3T system using ethylene glycol-filled phantoms. Background gradients were varied, and one phantom was uniformly heated to validate both compensation approaches. Independent temperature recordings were made with optical probes.ResultsErrors correlated closely to the background gradients in all experiments. Temperature distributions showed a much smaller standard deviation when the corrections were applied (0.21°C vs. 0.45°C) and correlated well with thermo-optical probes.ConclusionThe corrections offer the possibility to measure RF heating in phantoms more precisely. This allows mGE MRT to become a valuable tool in RF safety assessment.© 2014 Wiley Periodicals, Inc.

22 keywords...

hide…