Real-Time Tissue Change Monitoring on the Sonablate® 500 during High Intensity Focused Ultrasound (HIFU) Treatment of Prostate Cancer

Abstract

Sonablate® 500 (SB‐500) HIFU devices have been successfully used to treat prostate cancer non‐invasively. In addition, Visually Directed HIFU with the SB‐500 has demonstrated higher efficacy. Visually Directed HIFU works by displaying hyperechoic changes on the B‐mode ultrasound images. However, small changes in the grey‐scale images are not detectable by Visually Directed HIFU. To detect all tissue changes reliably, the SB‐500 was enhanced with quantitative, real‐time Tissue Change Monitoring (TCM) software. TCM uses pulse‐echo ultrasound backscattered RF signals in 2D to estimate changes in the tissue properties caused by HIFU. The RF signal energy difference is calculated in selected frequency bands (pre and post HIFU) for each treatment site. The results are overlaid on the real‐time ultrasound image in green, yellow and orange to represent low, medium and high degree of change in backscattered energy levels. The color mapping scheme was derived on measured temperature and backscattered RF signals fro...