Feasibility of inducing and imaging thermal strain for high-risk plaque identification in peripheral arteries using ultrasound arrays

The feasibility of inducing and imaging thermal strain to identify vulnerable plaques in peripheral arteries based on conventional ultrasound scanners is demonstrated. Vulnerable plaque usually consists of a large lipid-rich core. Because lipid-bearing tissue has a negative temperature dependence of sound speed, whereas water-based tissue has a positive one, thermal strain imaging can differentiate the two different types of tissues with high contrast and thus is useful for plaque composition characterization. In this study, we aimed at inducing thermal strain with the same linear array used for imaging to develop a thermal strain imaging system highly compatible with conventional scanners. Accordingly, we developed a technique to design ultrasound heating patterns based on linear programming. Simulation results based on a linear array (64 elements, 5 MHz, and 0.3-mm element spacing) show that raising the temperature in a region of interest (10 mm wide) 30 mm from the array by 1.9 °C within 1 second is possible even if the tissue is highly attenuating (e.g., 0.8 dB/MHz/cm).