Wide beam-harmonic motion imaging for locating focus of high intensity focused ultrasound:An in vitro study
Objective To observe the effectiveness of ultrasound wide beam(WB)-based harmonic motion imaging(HMI)(WB-HMI)for locating irradiation focus of high intensity focused ultrasound(HIFU)for in vitro tissue.Methods WB-HMI technology was developed with acoustic radiation force and ultrasound imaging as the key technology.For in vitro porcine tenderloin and bovine liver tissue,different amplitude modulation(AM)frequencies(25-100 Hz)and excitation acoustic power(0.7-28 W)were used to achieve WB-HMI localization of HIFU irradiation focus,and the differences of WB-HMI localization of HIFU irradiation focus under different parameter combinations were observed.Taken the actual focus position on ultrasonic image after HIFU as the standard and the focus positioning error＜1 mm as the effective standard of WB-HMI locating irradiation focus,the locating success rate was calculated.Results The larger the acoustic power,the larger the displacement amplitude of irradiation focus by WB-HMI at the same AM frequency,while the smaller the AM frequency,the larger the displacement amplitude of irradiation focus located by WB-HMI under the same acoustic power.Under different AM frequencies,for in vitro porcine tenderloin,the success rate of WB-HMI for locating HIFU radiation focus was higher than 90.00％when acoustic power was 15 W or 22 W,whereas the success rate showed a decreasing trend when the acoustic power was 28 W.For in vitro bovine liver tissue,the success rate of WB-HMI localization was 100％when acoustic power was ≥7.0 W.Conclusion WB-HMI could be used to effectively locate HIFU irradiation focus for isolated tissue.
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