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High intensity focused ultrasound (HIFU) is a promising technique for cancer treatment owing to its minimal invasiveness and safety. However, skin burn, long treatment time and incomplete ablation are main shortcomings of this method. This paper presents a novel HIFU robotic system for breast cancer treatment. The robot has 4 rotational degrees of freedom with the workspace located in a water tank for HIFU beam imaging and ablation treatment. The HIFU transducer combined with a diagnostic 2D linear ultrasound probe is mounted on the robot end-effector, which is rotated around the HIFU focus when ablating the tumor. HIFU beams are visualized by the 2D probe using beam imaging. Skin burn can be prevented or alleviated by avoiding long time insonification towards the same skin area. The time cost could be significantly reduced, as there is no need to interrupt the ablation procedure for cooling the skin. In addition, our proposed robot control strategies can avoid incomplete ablation. Experiments were carried out and the results showed the effectiveness of our proposed system.

High intensity focused ultrasound (HIFU) treatment is one minimally invasive treatment method for cancer. Visualizing the internal treatment area of a body during HIFU treatment is required in order to achieve appropriate beam positioning and HIFU dosage. The objective of this work is to develop an ultrasound monitoring system for thermally induced coagulation. Localized motion imaging (LMI) is a monitoring method used to detect a localized mechanical response that is dependent on changes in tissue stiffness caused by thermal coagulation. In LMI, amplitude modulated HIFU causes oscillation of tissues in the HIFU focal area. The elastic modulus at a coagulated area increases and can be detected as an area with decreased oscillation amplitude., Localized control of the oscillation by changing the modulation frequency was conducted to increase the detection sensitivity for small coagulated areas in porcine liver. 2 and 7.5 MHz transducers were employed for HIFU and imaging, respectively. The amplitude modulation frequency was changed in the range from 50 to 200 Hz. The acoustic intensity of HIFU was 2.0 kW/cm2 at the focus and the exposure time was 45 s. The decrease in the amplitude of tissue oscillation at the focal point was detected within 5-10 s of HIFU exposure at the highest modulation frequency. The detected amplitude was decreased to 0.2, which indicates that for LMI, a high modulation frequency is suitable for the detection of small coagulation areas or areas of initial coagulation.