Experimental Evaluation of an Array Transducer for Ultrasound Thermal Strain Imaging: Phantom and In Vivo Studies

Characterization of atherosclerosis plaque (AP) is critical for diagnosing rupture-prone AP that directly causes stroke and heart attack, and for guiding in-time interventions and avoiding unnecessary surgeries for stable cases. Ultrasound thermal strain imaging (US-TSI) is known to be capable of characterizing lipids, an important feature of rupture-prone AP. However, before translating US-TSI to in vivo clinical applications, significant technical challenges must be overcome, primarily the requirements of a well-controlled heating strategy to achieve a rapid, safe and spatial-temporal-precise local tissue temperature increase.

To address these issues, we recently developed a novel US-TSI transducer that integrates dual ultrasound heating arrays that use the thermal effect of the acoustic radiation force, and an ultrasound imaging array to reconstruct the spatial thermal strain map.

This article presents the first comprehensive test results of our new US-TSI transducer including benchtop US-TSI experiments on ultrasound gelatin phantoms with spatial temperature measurements to compare the thermal strain pattern and the corresponding 2-D temperature map, and US-TSI experiments on a pig with temperature measurements to verify the in vivo feasibility and safety further. A clear thermal strain pattern was obtained as a maximum of -0.25% in phantom and -0.08% in vivo, which corresponds with a reasonable temperature increase, 2.5°C in the phantom and 0.9°C in vivo. There was also a high resemblance between the thermal strain pattern and corresponding temperature measurements.

The results demonstrate the effectiveness and safety of performing US-TSI using our new array transducer.