Comparative study of temperature measurements inex vivoswine muscle and a tissue-mimicking material during high intensity focused ultrasound exposures

Abstract

Tissue-mimicking materials (TMMs) can provide a convenient, stable, and reproducible means for testing high intensity focused ultrasound (HIFU) devices. When TMMs containing thermal sensors are used to measure ultrasound-induced temperature rise, it is important that measurement results reasonably represent those that occur in biological tissue. Therefore the aim of this paper is to compare the thermal behavior of the TMM under HIFU exposure to that of ex vivo tissue. This was accomplished using both a previously developed TMM and fresh ex vivo swine muscle that were instrumented with bare 50 µm thin wire thermocouples. HIFU at 825 kHz was focused at the thermocouple junction. 30 s exposures of increasing peak negative pressure (1 to 5 MPa) were applied and the temperature profile during and after sonication was recorded. B-mode imaging was used to monitor bubble activity during sonication. If bubble formation was noted during the sonication, the sonication was repeated at the same pressure levels two more times at 20 min intervals. Temperature traces obtained at various pressure levels demonstrated similar types of heating profiles in both the tissue and TMM, the exact nature of which depended on whether bubbles formed during the HIFU exposure. The onset of bubble activity occurred at lower ultrasonic pressures in the TMM, but the basic temperature rise features due to HIFU exposure were essentially the same for both materials.

Computational Model for Tumor Oxygenation Applied to Clinical Data on Breast Tumor Hemoglobin Concentrations Suggests Vascular Dilatation and Compression

“…Following [98] a possible remedy to this problem might be to exclude root node geometries that result in unrealistic values of biophysical variables, e.g. unreasonably low or high perfusion rates.…”

Comparison between experimental and computational methods for the acoustic and thermal characterization of therapeutic ultrasound fields

“…The composition and characterization of the TMM have been described in previous publications. 24,25 The thermal conductivity and diffusivity of the TMM were quantified at room temperature with a thermal property analyzer (KD-2 PRO, Decagon Devices, Pullman, WA). The temperature rise was measured using a 75-lm diameter type E (chromel-constantan) embedded bare wire thermocouple (Omega Engineering, Stamford, CT) affixed through the center of a 5-cm thick, 8-cm diameter mold.…”

“…[29][30][31] When viscous heating or other thermocouple artifacts are present, back extrapolation of the measured cooling curve has been used to obtain the end-of-sonication (EOS) temperature. 25,32 In the present work, we fit the measured cooling curves to a function [see Eq. (1)] based on an established theoretical analysis of temperature rise in soft tissue.…”

Enhanced Heat Transfer and Thermal Dose Using Magnetic Nanoparticles During HIFU Thermal Ablation—An In-Vitro Study

“…Preclinical testing of HIFU systems has been performed using computational modeling [3][4][5][6][7], ex-vivo [8][9][10][11] or in-vivo [12][13][14][15] animal tissues, and tissue phantoms [16][17][18][19]. The advantage of using phantoms with tissue mimicking material (TMM) is that such test sections can be reused repeatedly without affecting acoustical and thermal properties, which can be made similar to that of human tissue [20].…”