Real-time visualization of a focused ultrasound beam using ultrasonic backscatter for monitoring of mechanical-based therapies

Mechanical-based focused ultrasound (FUS) therapies use mechanical interactions between an ultrasound wave and tissue to produce localized bioeffects. Although it is a promising therapeutic modality, mechanical-based FUS is limited due to a lack of cost-effective techniques to monitor the FUS beam in real-time during therapy. In this study, we present a technique for the real-time visualization of a FUS beam using ultrasonic backscatter, which could used for the qualitative monitoring of mechanical-based FUS therapies. A diagnostic imaging array was used to transmit a focused visualization pulse and the scattered signal was processed to reconstruct the intensity field of the FUS beam. The imaging array then captured a B-mode image that was registered with the beam reconstruction. The FUS beam reconstruction was superimposed onto the co-aligned B-mode image, allowing one to monitor the location of the FUS beam relative to anatomical information in the B-mode image. The effects of the echogenicity of the medium on the FUS beam reconstruction were reduced using an intensity mask derived from the B-mode image. FUS beam visualizations were demonstrated in a tissue-mimicking phantom and in vivo at a frame rate of 25-30 frames per second.