HIFU Focus Monitoring Based on Acoustic Radiation Force Pulse
FENG Lian1,2, ZHOU Fang1,2, CHEN Yanhua1,2, WANG Yongling3, ZHOU Xiaowei1,2
1. College of Biomedical Engineering, Chongqing Medical University, Chongqing 400016, China; 2. State Key Laboratory of
Ultrasound in Medicine and Engineering, Chongqing 400016, China; 3. National Engineering Research Center of Ultrasound
Medicine, Chongqing 401121, China
Abstract：Objective Through the in-vitro experiment, the feasibility of acoustic radiation force impulse imaging in detecting the
focal position of high intensity focused ultrasound (HIFU) before operation was validated. Methods The HIFU transducer was used
to generate acoustic excitation signals with time lengths of 200, 600 and 900 ms respectively. These sound waves generated acoustic
radiation force pulses inside the mimics and push the mimics tissue in the focal domain to shift. The motion imaging method (Loupas
two-dimensional cross-correlation algorithm) in ultrasonic imaging technology was used to monitor the displacement information.
Due to the large energy in the focal region, the displacement of the acoustic radiation force in the focal region was larger than that
outside the focal region. The focal region position was determined according to the two-dimensional spatial distribution of the tissue
motion amplitude. Results The displacement of acoustic radiation force pulse in the mimicked tissue could be monitored by the
ultrasound imaging technique, and the two-dimensional distribution map of tissue motion amplitude could accurately reflect the
focal position information of HIFU radiation. The focus position obtained by this method was 5 mm different from the geometric
focus of the transducer, which was closer to the actual focus. The results showed that the length of the excitation pulse had obvious
influence on the motion estimations. When the excitation time length was 200 ms, the tissue displacement distribution obtained was
most consistent with the actual energy distribution in the focal region. With the increase of the excitation time, the displacement
distribution showed a diffusion trend due to the influence of heat diffusion and tissue solidification. Conclusion By monitoring the
tissue movement caused by the acoustic radiation force of the HIFU radiation, the feasibility of preoperatively locating the focal point
is verified on the mimics, and the safety of HIFU surgery can be improved by using this technique.
