Purpose : We developed a quality assurance protocol for treating painful bone metastasis with a Magnetic Resonance-guided Focused Ultrasound Surgery (MRgFUS) system. The system delivers ultrasonic energy to heat the MR-delineated metastatic bone target up to 60 degrees Celsius and ablate periosteal nerve fibers for sustained pain control. In this protocol, equipments, calibration procedures, and recommended tolerance are reported. Materials and Methods : In this research, we measured sonication-induced temperature change in a homogenous phantom before and after Daily Quality Assurance (DQA) procedure performed in thirty-one treatment sessions in a single institute. Distances between ultrasonic focus and the spot with highest temperature (Focusing Error, FE) in the phantom were measured with magnetic resonance thermography. Result : DQA procedure effectively decrease FE (Pre-DQA group: 1.73±0.43 mm, DQA group: 0.43±0.12 mm, p-value＜0.01). Discussion : A comprehensive DQA procedure decreases focusing error and therefore guarantees treatment accuracy. It may translate into better patient safety and avoid unplanned heating of adjacent critical structures. We recommend that a FE of less than 1 mm should be achieved with DQA procedure before starting a MRgFUS treatment session.
- MRI-guided focused ultrasound surgery (MRgFUS)
- Daily Quality Assurance (DQA)
- Position stability