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Transurethral ultrasound therapy of the prostate in the presence of calcifications: a simulation study

Suomi, V; Treeby, B; Jaros, J; Makela, P; Anttinen, M; Saunavaara, J; Sainio, T; ... Blanco, R; + view all (2018) Transurethral ultrasound therapy of the prostate in the presence of calcifications: a simulation study. Medical Physics , 45 (11) pp. 4793-4805. 10.1002/mp.13183. Green open access

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Abstract

PURPOSE: Transurethral ultrasound therapy is an investigational treatment modality which could potentially be used for the localised treatment of prostate cancer. One of the limiting factors of this therapy is prostatic calcifications. These attenuate and reect ultrasound and thus reduce the efficacy of the heating. The aim of this study is to investigate how prostatic calcifications affect therapeutic efficacy, and to identify the best sonication strategy when calcifications are present. METHODS: Realistic computational models were used on clinical patient data in order to simulate different therapeutic situations with naturally occurring calcifications as well as artificial calcifications of different sizes (1-10 mm) and distances (5-15 mm). Furthermore, different sonication strategies were tested in order to deliver therapy to the untreated tissue regions behind the calcifications. RESULTS: The presence of calcifications in front of the ultrasound field was found to increase the peak pressure by 100% on average while the maximum temperature only rose by 9% during a 20-second sonication. Losses in ultrasound energy were due to the relative large acoustic impedance mismatch between the prostate tissue and the calcifications (1.63 vs. 3.20 MRayl) and high attenuation coeficient (0.78 vs. 2.64 dB/MHz1:1/cm), which together left untreated tissue regions behind the calcifications. In addition, elevated temperatures were seen in the region between the transducer and the calcifications. Lower sonication frequencies (1-4 MHz) were not able to penetrate through the calcifications effectively, but longer sonication durations (20-60 s) with selective transducer elements were effective in treating the tissue regions behind the calcifications. CONCLUSIONS: Prostatic calcifications limit the reach of therapeutic ultrasound treatment due to reections and attenuation. The tissue regions behind the calcifications can possibly be treated using longer sonication durations combined with proper transducer element selection. However, caution should taken with calcifications located close to sensitive organs such as the urethra, bladder neck or rectal wall. This article is protected by copyright. All rights reserved.

Type: Article
Title: Transurethral ultrasound therapy of the prostate in the presence of calcifications: a simulation study
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/mp.13183
Publisher version: https://doi.org/10.1002/mp.13183
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: calcification, efficacy, heating, prostate cancer, therapeutic ultrasound
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Med Phys and Biomedical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10056891
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