Blood flow imaging using singular value decomposition filter during high-intensity focused ultrasound exposure

High-intensity focused ultrasound (HIFU) is a minimally invasive treatment modality to induce thermal coagulation. In clinical cases, noninvasive blood flow occlusion was successfully achieved by HIFU exposure. However, it is difficult to monitor the blood flow during HIFU exposure due to the interference of HIFU noise with RF echo signals. In this study, we proposed a novel filtering method for monitoring blood flow during HIFU exposure by combining an singular value decomposition (SVD) filter with the HIFU noise reduction method. The HIFU noise was reducted by subtracting the RF signals of passive imaging from the RF signals of active imaging while keeping the tissue and blood flow signals intact. After that, the blood flow signals were identified by employing the SVD filter, on the basis of the spatiotemporal characteristics and amplitudes of these signals. The results imply that the proposed filtering method is useful for monitoring of blood flow during HIFU exposure.