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ARFI‐prepared MRgHIFU in liver: Simultaneous mapping of ARFI‐displacement and temperature elevation, using a fast GRE‐EPI sequence
Author(s) -
Auboiroux Vincent,
Viallon Magalie,
Roland Joerg,
Hyacinthe JeanNoël,
Petrusca Lorena,
Morel Denis R.,
Goget Thomas,
Terraz Sylvain,
Gross Patrick,
Becker Christoph D.,
Salomir Rares
Publication year - 2012
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.23309
Subject(s) - image resolution , materials science , acoustic radiation force , ultrasound , displacement (psychology) , intensity (physics) , biomedical engineering , nuclear magnetic resonance , optics , physics , medicine , acoustics , psychology , psychotherapist
Abstract MR acoustic radiation force imaging (ARFI) is an elegant adjunct to MR‐guided high intensity focused ultrasound for treatment planning and optimization, permitting in situ assessment of the focusing and targeting quality. The thermal effect of high intensity focused ultrasound pulses associated with ARFI measurements is recommended to be monitored on line, in particular when the beam crosses highly absorbent structures or interfaces (e.g., bones or air‐filled cavities). A dedicated MR sequence is proposed here, derived from a segmented gradient echo‐echo planar imaging kernel by adding a bipolar motion encoding gradient with interleaved alternating polarities. Temporal resolution was reduced to 2.1 s, with in‐plane spatial resolution of 1 mm. MR‐ARFI measurements were executed during controlled animal breathing, with trans‐costal successively steered foci, to investigate the spatial modulation of the focus intensity and the targeting offset. ARFI‐induced tissue displacement measurements enabled the accurate localization, in vivo, of the high intensity focused ultrasound focal point in sheep liver, with simultaneous monitoring of the temperature elevation. ARFI‐based precalibration of the focal point position was immediately followed by trans‐costal MR‐guided high intensity focused ultrasound ablation, monitored with a conventional proton resonance frequency shift MR thermometry sequence. The latter MR thermometry sequence had spatial resolution and geometrical distortion identical with the ARFI maps, hence no coregistration was required. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.