Real-time simultaneous therapy and imaging for noninvasive HIFU surgery of prostate tissue

To achieve real-time simultaneous therapy and imaging for noninvasive HIFU (High Intensity Focused Ultrasound) surgery, reflected HIFU signals received by an imaging transducer should be removed. In this paper, we demonstrate that these interference signals can be significantly reduced in the formed B-mode image by implementing coded excitation and notch filtering on reception. To show the feasibility of this technique, we also propose a design of an integrated image/HIFU phased array transducer for treatment of malignant prostate tissues. A 14.4 mm x 28 mm prototype integrated image/HIFU transducer was built which consists of three single elements as preliminary experiments. When HIFU and imaging transducers were activated simultaneously, high amplitude 4 MHz and 8 MHz signals were detected by the 6 MHz imaging transducer. After notch filtering, one scanline produced by the 13-bit Barker code excitation with 2 cycles or 3 cycles per bit displayed a sidelobe level less than -40 dB, while the conventional 2-cycle sinusoidal pulse excitation produced a maximum sidelobe level of -30 dB. These results agree with those obtained with a Field II simulation.