Evaluating acoustic and thermal properties of a plaque phantom

Abstract

Purpose: The aim of this study is to evaluate the acoustic and thermal properties of a plaque phantom. This is very important for the effective implementation of ultrasound not only in diagnosis but especially in treatment for the future.

Material and methods: An evaluation of acoustic and thermal properties of plaque phantoms to test their suitability mainly for ultrasound imaging and therapy was presented. The evaluation included measurements of the acoustic propagation speed using pulse-echo technique, ultrasonic attenuation coefficient using through transmission immersion technique, and absorption coefficient. Moreover, thermal properties (thermal conductivity, volumetric specific heat capacity and thermal diffusivity) were measured with the transient method using a needle probe.

Results: It was shown that acoustic and thermal properties of atherosclerotic plaque phantoms fall well within the range of reported values for atherosclerotic plaque and slightly different for thermal diffusivity and volumetric specific heat capacity for soft tissues. The mean value of acoustic and thermal properties and their standard deviation of plaque phantoms were 1523 ± 23 m/s for acoustic speed, 0.50 ± 0.02 W/mK for thermal conductivity, 0.30 ± 0.21 db/cm-MHz for ultrasonic absorption coefficient and 1.63 ± 0.46 db/cm-MHz for ultrasonic attenuation coefficient.

Conclusions: This study demonstrated that acoustic and thermal properties of atherosclerotic plaque phantoms were within the range of reported values. Future studies should be focused on the optimum recipe of the atherosclerotic plaque phantoms that mimics the human atherosclerotic plaque (agar 4% w/v, gypsum 10% w/v and butter 10% w/v) and can be used for HIFU therapy.

Keywords: Absorption; Attenuation; Conductivity; Phantoms; Plaque; Ultrasound.

Fig. 1

Schematic diagram of the experimental set-up used for measurement of the acoustic propagation speed

Fig. 2

Experimental set-up used for measurement of the attenuation coefficient of different plaque phantoms

Fig. 3

Schematic diagram of the experimental set up to measure the absorption coefficient of the plaque phantoms

Fig. 4

a Thermal conductivity, b Volumetric specific heat capacity and c Thermal diffusivity of plaque phantoms against butter concentration for 10% w/v and 6% w/v gypsum respectively

Fig. 5

a Thermal conductivity, b Volumetric specific heat capacity and c Thermal diffusivity of plaque phantoms against agar for 10% w/v lipid and 10% w/v gypsum

Fig. 6

a Thermal conductivity, b Volumetric specific heat capacity and c Thermal diffusivity of plaque phantoms against gypsum for 10% w/v and 18% w/v butter respectively

Fig. 7

a Absorption coefficient, b Attenuation coefficient and c Acoustic propagation speed of plaque phantoms against lipid concentration. Agar and gypsum was 4% w/v and 6% w/v respectively

Fig. 8

a Absorption coefficient, b Attenuation coefficient and c acoustic propagation speed of plaque phantoms against agar concentration. Gypsum and butter was 6 and 15% w/v respectively

Fig. 9

a Absorption coefficient, b Attenuation coefficient and c acoustic propagation speed of plaque phantoms against gypsum concentration. Agar and butter concentration was 4% w/v and 15% w/v respectively