Temperature elevation by HIFU in ex vivo porcine muscle: MRI measurement and simulation study. Issue 5 (18th April 2014)

• Record Type: Journal Article
• Authors: Solovchuk, Maxim A.; Hwang, San Chao; Chang, Hsu; Thiriet, Marc; Sheu, Tony W. H.
• Is Part Of: Medical physics. Volume 41:Issue 5(2014)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2014-04-18
• Subjects: Clinical applications -- Muscles -- Biological effects of acoustic and ultrasonic energy -- Biomedical instrumentation and transducers, including micro‐electro‐mechanical systems (MEMS); biomedical MRI -- biomedical transducers -- computational fluid dynamics -- muscle -- ultrasonic therapy -- ultrasonic transducers; HIFU -- Westervelt equation -- magnetic resonance guided high intensity focused ultrasound -- porcine muscle; Involving electronic [emr] or nuclear [nmr] magnetic resonance, e.g. magnetic resonance imaging -- Ultrasound therapy -- Processes or apparatus for generating mechanical vibrations of infrasonic, sonic or ultrasonic frequency -- Biological material, e.g. blood, urine; Haemocytometers; Temperature measurement -- Magnetic resonance imaging -- Transducers -- Medical imaging -- Tissues -- Ultrasonography -- Focal points -- Muscles -- Nonlinear acoustics -- Ultrasonic transducers; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4870965
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: : High‐intensity focused ultrasound is a rapidly developing medical technology with a large number of potential clinical applications. Computational model can play a pivotal role in the planning and optimization of the treatment based on the patientˈs image. Nonlinear propagation effects can significantly affect the temperature elevation and should be taken into account. In order to investigate the importance of nonlinear propagation effects, nonlinear Westervelt equation was solved. Weak nonlinear propagation effects were studied. The purpose of this study was to investigate the correlation between the predicted and measured temperature elevations and lesion in a porcine muscle. Methods: : The investigated single‐element transducer has a focal length of 12 cm, an aperture of 8 cm, and frequency of 1.08 MHz. Porcine muscle was heated for 30 s by focused ultrasound transducer with an acoustic power in the range of 24–56 W. The theoretical model consists of nonlinear Westervelt equation with relaxation effects being taken into account and Pennes bioheat equation. Results: : Excellent agreement between the measured and simulated temperature rises was found. For peak temperatures above 85–90 °C "preboiling" or cavitation activity appears and lesion distortion starts, causing small discrepancy between the measured and simulated temperature rises. From the measurements and simulations, it was shown that distortion of the lesion was caused by the "preboiling" activity. Conclusions: : The present study demonstrated that for peak temperatures below 85–90 °C numerical simulation results are in excellent agreement with the experimental data in three dimensions. Both temperature rise and lesion size can be well predicted. Due to nonlinear effect the temperature in the focal region can be increased compared with the linear case. The current magnetic resonance imaging (MRI) resolution is not sufficient. Due to the inevitable averaging the measured temperature can be 10–30 °C lower than the peak temperature. Computational fluid dynamics can provide additional important information that is lost using a state of the art MRI device.