Study on High-Intensity Focused Ultrasound Focal Position Control Using Intracorporeal Acoustic Device

High-intensity focused ultrasound (HIFU) is widely used in cancer therapies, and it is hoped that its noninvasiveness will allow it to be applied to other clinical domains. Because HIFU is percutaneously delivered in the treatment of the liver, breast and uterus, there is a problem with the ultrasound beam being deflected or attenuated during its travel. In contrast, the intracorporeal use of an HIFU device provides an obstacle-free path, but the focal length is limited because of size constraints. In this paper, we propose the use of an intracorporeal device equipped with an acoustic mirror or lens to allow the ultrasound energy delivered through the abdominal wall to be reflected or focused in the body. The insertion of such a device into the body requires a small incision, but the proposed concept can help to safely control the HIFU focal point in the treatment of deep-seated organs. Moreover, safety is ensured because the device is electrically isolated. We have developed an experimental setup where the intracorporeal device is robotically positioned in front of an HIFU transducer. In preliminary experiments, the focused ultrasound energy was reflected using a metal plate, and the planar ultrasound waves were focused using an acrylic biconcave lens, with Schlieren imaging used for visualisation, and the results demonstrated the proof of concept.