Shift of Focus Region (SFR) in Heated Tissues by High Intensity Focused Ultrasound (HIFU)

In high intensity focused ultrasound (HIFU) experiments it is found that the center of the heated region is always deviated from the geometrical focus point of transducers. This phenomenon is called the shift of the focus region (SFR). To achieve optimal result in HIFU treatment, the focused region should be adjusted to compensate the shift. In this paper, a quantitative method to measure SFR is proposed and applied to the experiments for porcine tissues in vitro by the authors. In the experiments it is observed that the maximum SFR which are towards to the HIFU transducer can exceed 1 cm.