Therapy planning and monitoring of tissue ablation by high intensity focused ultrasound (HIFU) using imaging and simulation.

High intensity focused ultrasound (HIFU) 'cooks' or ablates the target tissue at the focus of the ultrasound beam by thermal and cavitation effects. The HIFU is emerging as a non-invasive method for tumor ablation. The HIFU application for tissue ablation requires tools for dosimetry therapy planning, and real-time feedback of the intended and actual target tissues. Pretreatment planning is an important step for a successful HIFU therapy outcome. Typically, the therapy planning approach involves the use of pretreatment imaging data, defining the target and surrounding tissues by manual or semiautomatic segmentation, development of a 3-D anatomy model of the region of interest from segmentation or registration with a reference dataset, simulation of the HIFU beam and thermal dosimetry around the target tissue, display and 3-D visualization of imaging and simulation data, and review of the treatment plan options. Recent developments in therapy planning using imaging are targeted for specific applications such as prostate cancer using 3-D ultrasound images and uterine fibroids using MRI. However, significant developments have been accomplished in image guidance and feedback during the delivery of HIFU treatments. This talk reviews recent work towards therapy planning and presents approaches for developing strategies for HIFU therapy. It describes general and target-specific techniques and software tools for HIFU treatment planning using pretherapy imaging, and monitoring and controlling the HIFU delivery and tissue lesion using 1D, 2D and 3D ultrasound imaging. This aids development of optimized, high-precision HIFU applications for a controlled ablation of the target tumor. It also potentially reduces the overall treatment duration and exposure to non-target tissues.