Numerical estimation of HIFU focal error for breast cancer treatment

A numerical estimation of focal error after the propagation though breast tissue to realize precise focal control of HIFU (High Intensity Focused Ultrasound) targeting breast cancer was described. Breast model was constructed from a 3D MRI clinical breast data. All pixel intensity was assigned to 4 kinds of typical material; water, connective tissue, fat and glandula mammaria. HIFU simulator based on a finite-time-domain-method was employed. A 56-chnannel HIFU transducer with both aperture width and focal length were 100 mm and with a center frequency of 2 MHz was used. Three separated peaks were observed after propagation of breast tissue. The focal shift amount was a few millimeter in both lateral and propagation directions. To confirm the relation between the acoustical inhomogeneous and the focal error, time reversal method was employed. The results showed that focal error was successfully suppressed by time reversal method.