Correction of proton resonance frequency shift MR‐thermometry errors caused by heat‐induced magnetic susceptibility changes during high intensity focused ultrasound ablations in tissues containing fat. Issue 6 (17th December 2013)

• Record Type: Journal Article
• Authors: Baron, Paul; Deckers, Roel; de Greef, Martijn; Merckel, Laura G.; Bakker, Chris J.G.; Bouwman, Job G.; Bleys, Ronald L.A.W.; van den Bosch, Maurice A.A.J.; Bartels, Lambertus W.
• Is Part Of: Magnetic resonance in medicine. Volume 72:Issue 6(2014:Dec.)
• Page Start: 1580
• Page End: 1589
• Publication Date: 2013-12-17
• Subjects: Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.25063
• Languages: English
• ISSNs: 0740-3194

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="mrm25063-sec-0001" sec-type="section"> <title>Purpose</title> <p>In this study, we aim to demonstrate the sensitivity of proton resonance frequency shift (PRFS) ‐based thermometry to heat‐induced magnetic susceptibility changes and to present and evaluate a model‐based correction procedure.</p> </sec> <sec id="mrm25063-sec-0002" sec-type="section"> <title>Theory and Methods</title> <p>To demonstrate the expected temperature effect, field disturbances during high intensity focused ultrasound sonications were monitored in breast fat samples with a three‐dimensional (3D) gradient echo sequence. To evaluate the correction procedure, the interface of tissue‐mimicking ethylene glycol gel and fat was sonicated. During sonication, the temperature was monitored with a 2D dual flip angle multi‐echo gradient echo sequence, allowing for PRFS‐based relative and referenced temperature measurements in the gel and T<sub>1</sub>‐based temperature measurements in fat. The PRFS‐based measurement in the gel was corrected by minimizing the discrepancy between the observed 2D temperature profile and the profile predicted by a 3D thermal model.</p> </sec> <sec id="mrm25063-sec-0003" sec-type="section"> <title>Results</title> <p>The HIFU sonications of breast fat resulted in a magnetic field disturbance which completely disappeared after cooling. For the correction method, the 5th to 95th percentile interval of the PRFS‐thermometry error in the gel decreased from 3.8°C before correction to 2.0–2.3°C after correction.</p> </sec> <sec id="mrm25063-sec-0004" sec-type="section"> <title>Conclusion</title> <p>This study has shown the effects of magnetic susceptibility changes induced by heating of breast fatty tissue samples. The resultant errors can be reduced by the use of a model‐based correction procedure. Magn Reson Med 72:1580–1589, 2014. © 2013 Wiley Periodicals, Inc.</p> </sec> </abstract>