Ultrasonic Image Enhanced by Shockwave-induced Cavitation

Wen-Shiang Chen ； Ping-Mo Ma ； Chih-Kuang Yeh

《Journal of Medical and Biological Engineering》 25卷4期 (2005/12) Pp. 143-151

並列摘要

We report the use of high-intensity sound waves, such as shockwaves or high-intensity focused ultrasound (HIFU), to enhance the signal-to-noise ratio of structures by generating contrast-agent-like free air bubbles in a gel phantom and ex-vivo liver tissue. The focus of a shockwave or HIFU transducer is small, and thus the energy can be directed at and limited to a small region. The contrast of a specific location can therefore be selectively enhanced by the generation of air bubbles with high scattering ability. As few as 10 shockwave pulses are necessary for the generation of a maximal scattering signal. The scattering signal disappeared after about 5 s for pulses longer than 10 cycles, and simulations revealed that the shockwave-generated bubbles had an average radius of 10 μm. We also demonstrate how shockwave-induced cavitation can be used to detect the presence of water in an in-vitro cyst model. Shockwave-generated bubbles can be clearly detected by a diagnostic ultrasound scanner in a cavity filled with air-soluble fluid, but not in one filled with glycerol. Furthermore, the cavitation properties of a cavity filled with blood differ with the stage of coagulation. To avoid the pain caused by shockwaves, short ultrasound pulses generated by a HIFU transducer could also be used, which showed satisfactory results in ex-vivo liver tissue. To detect an even smaller structure, low-concentration ultrasound contrast agent could be used to increase the number of the cavitation nuclei and generated enough inertial cavitation. This new method of ultrasonic imaging may be useful for the targeting purpose during the therapeutic applications of HIFU or shockwaves.

並列關鍵字

Inertial cavitation ； Shockwave ； Bubbles ； High-intensity focused ultrasound