Real-time 3D image-guided HIFU therapy.

Real-time three-dimensional ultrasound imaging (4D US) was utilized to monitor the treatment site during high-intensity focused ultrasound (HIFU) treatment. To obtain real-time monitoring during HIFU sonication, a 4D US imaging system and HIFU were synchronized and interference on the US image adjusted so that the region of interest was visible during treatment. The system was tested using tissue mimicking phantom gels and chicken breast tissue. The 4D US showed hyperechoic spots at the focal region of the HIFU transducer which then slowly faded after HIFU treatment. The hyperechoic regions were used as an indication of coagulative necrosis which occurs at temperatures higher than 60 degrees C. Different intensities of HIFU were applied to observe the difference in lesion formation and to determine the threshold intensity that produced hyperechoic regions due to the thermal and mechanical effects of focused ultrasound waves. The position, orientation, and shape of various lesions were examined in the three dimensional ultrasound images, and the volume of the lesions was measured. These volumes were compared to the volume measurements obtained from dissection of the tissue and phantom gels.