Ultrasound characterization of coronary artery wall in vitro using temperature-dependent wave speed

Abstract

Temperature dependence of the speed of sound, @c=@T , is examined as a parameter to characterize tissue-equivalent phantoms and coronary artery tissue in vitro. The experimental system comprises an ultrasound biomicroscope, operating at center frequency of 50 MHz, and a temperature controlled micropositioning sample cell. Radio frequency (RF) backscattered signals were recorded, with a digital oscilloscope, from 64 independent positions and at 5 temperatures starting at 31 C (phantom) and 36 C (tissue) in steps of one degree. Time shift per degree Celsius ( t= T ) was obtained with a correlation technique applied between gated sections of two RF-signals collected with one degree temperature difference from the same location in the sample. The average h t= Ti, calculated for every position of the gated sections along the propagation axis of the ultrasound beam, has the slope proportional to the difference between the linear coefficient of thermal expansion and the thermal sensitivity of the speed of sound. Calibration measurements of @ c = @ T , made with single-and three-layer tissue equivalent phantoms, correlated well (r 0:91) with those measured by the time-offlight substitution method. The @ c = @ Twas estimated for the three layers on the wall of eight samples of human coronary arteries, obtained at autopsy from four individuals.The @c=@T for the intima layers decreases as the disease progresses from mild intimal thickening to a more advanced atherosclerosis.

Motion artifact reduction for IVUS-based thermal strain imaging

“…Due to TSI's strong contrast between lipid-bearing and water-bearing tissue, it may potentially resolve the lipid-laden pool within a ruptureprone plaque. Initial results by our and other groups demonstrated the possibility of plaque identification with this technique [21]- [23]. Further clinical validation is required.…”

Ultrasound guidance and monitoring of laser‐based fat removal

“…In contrast, speed of sound decreases in bovine fat at À7.4 m/(s 8C). Since the temperature-dependent speed of sound varies significantly between different tissue types, ultrasound-based methods for tissue characterization are possible based on general composition of water-based and lipid-based tissues [14,15]. Specifically, by tracking the time shifts in ultrasound signal arrival (which is the result of temperature-induced change in the speed of sound), subdermal fat and water/collagen rich dermis can potentially be differentiated with high contrast.…”

“…Ultrasound is a real-time, non-invasive imaging modality that is typically employed in the diagnosis of tissue abnormalities and identification of pathological tissue [12,13]. Ultrasound imaging has also been utilized for tissue characterization based on temperature dependent changes of the speed of sound in tissue [14,15]. In addition, ultrasound imaging has been recently proposed to monitor the temperature increase in response to laser irradiation [16][17][18].…”

Computer-aided tissue characterization using ultrasound-induced thermal effects: analytical formulation and in-vitro animal study

“…The model is based on formulations that describe the dependence of tissue sound speed on temperature. 3 Similar formulations have been used by Pereira et al 4 to develop an idealized tissue characterization procedure. In this procedure, they employed a temperature-controlled water bath to change the temperature of coronary artery tissue samples and a 50 MHz ultrasound imaging system to quantify the change in tissue sound speed as a function of temperature.…”