Temperature Measurement Using Passive Harmonics during High Intensity Focused Ultrasound Exposures in Porcine Tissue
Hu Donga, b, Shengyou Qiana, Qiaolai Tana, Xiao Zoua, Bei Liua
aCollege of Physics and Information Science, Hunan Normal University, Changsha 410081, PR China
bDepartment of Information and Engineering, Changsha Normal University, Changsha 410100, PR China
Received: February 26, 2018; in final form July 14, 2018
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It is important to deliver suitable thermal dose to target region during high intensity focused ultrasound therapy,and ultrasonic non-invasive temperature measurement is an easily accepted approach to monitor the temperature fields during the treatment process. Traditional method usually required another source for monitoring besides high intensity focused ultrasound source. This paper was based on passive scattering harmonics for high intensity focused ultrasound temperature measurement, and it could avoid the influence of treatment sources on temperature measurement. The purpose of this paper is to investigate the relationship between the nonlinear harmonic amplitude and temperature in porcine tissue (muscle and liver). The optical fiber hydrophone was used to receive passive scattering harmonics from high intensity focused ultrasound irradiation in porcine tissue, and the temperature of tissue in focal region was measured with a thermocouple needle at the same time. The relationship between harmonic amplitude and temperature was analyzed. Experimental results indicate that the values of amplitude for fundamental wave P1, the second harmonic P2, the third harmonic P3, the ratios of P2/P1, P3/P1, and P3/P2 decrease while temperature increases in the focal region of porcine tissue, and the slope of P2/P1, P3/P1, and P3/P2 have obvious decline at the beginning of temperature measurement, but their slope become flat as temperature increases, and the slope of P2/P1, P3/P1, and P3/P2 drop faster in porcine muscle than in liver. This study may potentially be used as an non-invasive method of temperature monitoring for ultrasonic thermal therapy in real-time.

topics: high intensity focused ultrasound, temperature measurement, passive harmonic