In recent years, noninvasive thermal treatment by using high-intensity focused ultrasound (HIFU) has high potential in tumor treatment. The goal of this research is to develop an ultrasound imaging-guided robotic HIFU ablation system for tumor treatment. The system integrates the technologies of ultrasound image-assisted guidance, robotic positioning control, and HIFU treatment planning. With the assistance of ultrasound image guidance technology, the tumor size and location can be determined from ultrasound images as well as the robotic arm can be controlled to position the HIFU transducer to focus on the target tumor. After the development of the system, several experiments were conducted to measure the positioning accuracy of this system. The results show that the average positioning error is 1.01 mm with a standard deviation 0.34, and HIFU ablation accuracy is 1.32 mm with a standard deviation 0.58, which means this system is confirmed with its possibility and accuracy.

Introduction In recent years, high-intensity focused ultrasound (HIFU) has commonly been applied in non-invasive tumor therapy, such as to treat uterine fibroids or prostate tumors. However, respiration may cause tumor displacement, such as liver tumor displacement, which may lead to errors in localization or inadequate thermal effects on the tumor. Therefore, a compensating mechanism for target localization is important. Methods This paper introduces an ultrasound imaging-assisted robotic HIFU ablation system with a displacement compensatory mechanism. According to the correlation between the measured displacements of the heaving chest and the target tumor, a respiration simulation device was designed, which used a tumor phantom and a cam-driving mechanism to simulate displacements of the tumor and of the heaving chest. Then, a polynomial function of the tumor position relative to the position of the heaving chest was generated. After the coordinate frames of the robotic arm, optical tracker and tumor phantom had been registered, the robotic arm was able to guide the HIFU probe to track and ablate the target tumor automatically and synchronously by inputting the displacement values of the heaving chest. Results The average positioning error in the single-point tracking experiment was 1.72 ± 1.26 mm, while the ablation temperature was stabilized at 80 °C. Furthermore, the average positioning error in the cross-section ablation experiment was 3.04 ± 1.24 mm.