A radiation force balance calibrator (100) for calibrating a high intensity focused ultrasound transducer (106), the radiation force balance calibrator comprising: a balance frame (130) a force sensor (138) for measuring force, wherein the force sensor is attached to the balance frame a balance (124) with first (132) and second ends (134), wherein the first end is attached to a pivot (128) for enabling the balance to pivot relative to the balance frame, wherein the second end is adapted for exerting force onto the force sensor an oil target phantom (116) connected to the balance for absorbing ultrasound radiation (112, 114) from the high intensity focused ultrasound transducer, wherein the absorption of ultrasonic radiation causes a reduction in the force exerted by the balance on the force sensor and wherein the radiation force balance calibrator is constructed of non-magnetic materials.
