Magnetic resonance guided focused ultrasound surgery. Ablation of soft tissue at bone-muscle interface in a porcine model.

BACKGROUND: Pain management treatments of patients with bone metastases have either efficacy problems or significant side effects. Percutaneous radiofrequency ablation has recently proved to be of palliative value. Magnetic resonance guided focused ultrasound surgery (MRgFUS) uses focused ultrasonic energy to non-invasively create a heat-coagulated lesion deep within the body in a controlled, accurate manner. The surgeon can monitor and control energy deposition in real time. This technology represents a potential treatment modality in oncological surgery. We investigated the ability of two MRgFUS methods to accurately and safely target and ablate soft tissue at its interface with bone. MATERIALS AND METHODS: Heat-ablated lesions were created by MRgFUS at the bone-muscle interface of 15 pigs. Two different methods of energy delivery were used. Temperature rise at the target adjacent to bone was monitored by real time MR thermal images. Results were evaluated by MRI (magnetic resonance imaging), nuclear scanning and by histopathological evaluation. RESULTS: Soft tissue lesion sizes by both methods were in the range of 1-2 cm in diameter. Targeting the focus 'behind' the bone, achieved the same result with a single sonication only. Follow up MRI and histopathological examination of all lesions showed focal damage at its interface with bone and localized damage to the outer cortex on the side closer to the targeted tissue. There was no damage to non-targeted tissue. CONCLUSION: MRgFUS by both energy deposition methods can be used to produce controlled well-localized damage to soft tissue in close proximity to bone, with minimal collateral damage.

MR-guided focused ultrasound surgery (MRgFUS) for the palliation of pain in patients with bone metastases--preliminary clinical experience.

BACKGROUND: Magnetic resonance-guided focused ultrasound surgery (MRgFUS) is a noninvasive thermal ablation technique, shown to be clinically effective in the treatment of uterine fibroids and is being evaluated as a method of thermal ablation of benign and malignant breast tumors. To evaluate the safety and initial efficacy of MRgFUS for the palliation of pain caused by bone metastases, in patients for whom other treatments are either not effective or not feasible. MATERIALS AND METHODS: Thirteen patients suffering from symptomatic bone metastases underwent MRgFUS procedure. Treatment safety was evaluated by assessing the incidence and severity of device-related complications up to 6 months after treatment. Effectiveness of pain palliation was evaluated by visual analog scale, pain questionnaires and changes in the patients' medication. RESULTS: Fifteen procedures were carried out. Mean follow-up was 59 days. Twelve patients received adequate treatment and were available for follow-up. Two patients died due to disease progression during the first month after treatment. No severe adverse events were recorded. The remaining 10 patients reported prolonged improvement in pain score and/or reduced analgesic dosage. CONCLUSION: MRgFUS may provide a safe and effective noninvasive alternative for the palliation of pain, caused by bone metastases.