A localization method of lesions induced by High Intensity Focused Ultrasound based on acoustic backscatter change

High Intensity Focused Ultrasound (HIFU) has been investigated as a therapeutic modality for many medical applications. We investigated a noninvasive technique for the localization of HIFU-induced lesions based on the change in backscattered radio frequency (RF) signals. HIFU was applied to chicken breast tissue and we compared lesion locations obtained from RF data with our processing method, from the dissected tissues after exposure, and from B-mode images if exposures had resulted in hyperecho. RF amplitude of the focal spot was found to decrease, even without hyperecho in B-mode images. No significant difference was found on localization accuracy between the RF-based and the hyperecho-based method (p=0.76). In cases without hyperecho, the distance between RF-based locations and measured physical lesion locations was 3.37 +/- 1.59 mm. The axial and lateral difference was 2.00 +/- 2.31 mm and 0.85 +/- 2.15 mm, respectively, and no statistically significant difference was found between lesion coordinates in the axial (p=0.37) and lateral (p=0.15) directions. Based on the ex vivo tissue experiments, we have demonstrated the feasibility of the proposed RF-based method for the localization of the center of HIFU-induced lesions.