title: Development and validation of a MRgHIFU non-invasive tissue acoustic property estimation technique.
abstract: MR-guided high-intensity focussed ultrasound (MRgHIFU) non-invasive ablative surgeries have advanced into clinical trials for treating many pathologies and cancers. A remaining challenge of these surgeries is accurately planning and monitoring tissue heating in the face of patient-specific and dynamic acoustic properties of tissues. Currently, non-invasive measurements of acoustic properties have not been implemented in MRgHIFU treatment planning and monitoring procedures. This methods-driven study presents a technique using MR temperature imaging (MRTI) during low-temperature HIFU sonications to non-invasively estimate sample-specific acoustic absorption and speed of sound values in tissue-mimicking phantoms. Using measured thermal properties, specific absorption rate (SAR) patterns are calculated from the MRTI data and compared to simulated SAR patterns iteratively generated via the Hybrid Angular Spectrum (HAS) method. Once the error between the simulated and measured patterns is minimised, the estimated acoustic property values are compared to the true phantom values obtained via an independent technique. The estimated values are then used to simulate temperature profiles in the phantoms, and compared to experimental temperature profiles. This study demonstrates that trends in acoustic absorption and speed of sound can be non-invasively estimated with average errors of 21% and 1%, respectively. Additionally, temperature predictions using the estimated properties on average match within 1.2 °C of the experimental peak temperature rises in the phantoms. The positive results achieved in tissue-mimicking phantoms presented in this study indicate that this technique may be extended to in vivo applications, improving HIFU sonication temperature rise predictions and treatment assessment.
authors.affiliation: a Department of Bioengineering , University of Utah , Salt Lake City , UT , USA ;
authors.forename: Sara L
authors.initials: SL
authors.lastname: Johnson
authors.affiliation: b Department of Radiology and Imaging Sciences , University of Utah , Salt Lake City , UT , USA ;
authors.forename: Christopher
authors.initials: C
authors.lastname: Dillon
authors.affiliation: b Department of Radiology and Imaging Sciences , University of Utah , Salt Lake City , UT , USA ;
authors.forename: Henrik
authors.initials: H
authors.lastname: Odéen
authors.affiliation: b Department of Radiology and Imaging Sciences , University of Utah , Salt Lake City , UT , USA ;
authors.forename: Dennis
authors.initials: D
authors.lastname: Parker
authors.affiliation: a Department of Bioengineering , University of Utah , Salt Lake City , UT , USA ;|c Department of Electrical and Computer Engineering , University of Utah , Salt Lake City , UT , USA.
authors.forename: Douglas
authors.initials: D
authors.lastname: Christensen
authors.affiliation: b Department of Radiology and Imaging Sciences , University of Utah , Salt Lake City , UT , USA ;
authors.forename: Allison
authors.initials: A
authors.lastname: Payne
mesh_terms: D000162:Acoustics; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D013010:Sonication; D013696:Temperature
keywords: High intensity focused ultrasound; acoustic properties; non-invasive; thermal ablation; treatment planning