An Ultrasound-Guided Robotic HIFU Ablation System with Respiration Induced Displacement and Time Delay Compensation

Abstract

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.

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