Experimental verification of enhancement of HIFU-induced heating of tissue mimicking phantoms due to acoustic nonlinearity

• Published in: The Journal of the Acoustical Society of America 2004-05, Vol.115 (5_Supplement), p.2449-2449
• Main Authors: Sinilo, Tatiana V., Khokhlova, Vera A., Sapozhnikov, Oleg A.
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4782216

A possibility of enhancement of heat deposition of high-intensity focused ultrasound (HIFU) in tissue mimicking phantoms due to acoustic nonlinearity is experimentally studied. A gelatin sample of high concentration was used to model medium with acoustic properties similar to those of biological tissue. Several sets of pulse-periodic regimes with the same mean power but different pulse amplitudes and durations were used. In regimes with higher amplitudes (lower duty cycles), the waveform in the focal region was more strongly distorted because of acoustic nonlinearity. In the linear medium all the regimes of one set would give the same heating. Optical shadow pictures of the HIFU-heated region were taken in the regimes with different duty cycles but the same mean power. The heated region size increased for lower duty cycles, but the shadow shape remained regularly cigar-like in all the regimes, even when the ultrasound waveform was shocked. The transmitted signal measured by a hydrophone was stable. This showed that cavitation was not pronounced. Thermocouple measurements and theoretical modeling of gelatin temperature in the focal region of the ultrasound beam showed significant increase of HIFU heat deposition in the presence of shocks in the waveform. [Work supported by CRDF and RFBR.]