Treatment planning and patient positioning for MR-guided high intensity focused ultrasound treatment: a systematic approach

Background/introduction Treatment duration as well as time spent on patient positioning imposes limitations on therapeutic use of MRguided High Intensity Focused Ultrasound (MR-HIFU). Reduction of overall treatment time is especially important in potential pediatric applications and in other cases where general anesthesia must be used, due to the risks associated with prolonged anesthesia. Typically, up to 4 hours are allotted for the procedure, with patient positioning and treatment planning requiring an hour or more. If re-positioning is required during treatment, acquisition of needed images and re-planning of treatment may require 30 minutes or longer before ablation can resume. These delays limit the total time allowed for treatment, limiting the size of tumors that can be treated and increasing the risks as well as the cost of the procedure. The aim of this study is to evaluate the information needed to accurately plan MR-HIFU ablation of solid extremity tumors and to rationally design a practical approach to patient positioning for such treatments.