Motion Compensation for Real Time Ultrasound Scanning in Robotically Assisted Prostate Biopsy Procedures
Matija Markulin, Luka Matijević, Luka Siktar, Janko Jurdana, Branimir Caran, Marko Švaco, Filip Šuligoj, Bojan Šekoranja
TL;DR
The work addresses operator-dependent accuracy in ultrasound-based prostate biopsy by introducing a two-robot system that autonomously scans the prostate with active motion compensation. It combines force control and visual positioning to maintain consistent probe contact and uses MicroSegNet for segmentation of US images to generate a 3D prostate point cloud for planning, validated through ICP-based registration across stationary and motion scenarios. Key findings show robust motion tracking with submillimeter-to-millimeter RMSE and a persistent ~0.5 s delay, and successful 3D reconstruction under movement, though performance degrades when comparing moving to stationary scans. The study demonstrates feasibility of automated, motion-robust prostate US scanning and outlines concrete paths for future enhancements, including sensor augmentation, nonlinear control, and clinical testing.
Abstract
Prostate cancer is one of the most common types of cancer in men. Its diagnosis by biopsy requires a high level of expertise and precision from the surgeon, so the results are highly operator-dependent. The aim of this work is to develop a robotic system for assisted ultrasound (US) examination of the prostate, a prebiopsy step that could reduce the dexterity requirements and enable faster, more accurate and more available prostate biopsy. We developed and validated a laboratory setup with a collaborative robotic arm that can autonomously scan a prostate phantom and attached the phantom to a medical robotic arm that mimics the patient's movements. The scanning robot keeps the relative position of the US probe and the prostate constant, ensuring a consistent and robust approach to reconstructing the prostate. To reconstruct the prostate, each slice is segmented to generate a series of prostate contours converted into a 3D point cloud used for biopsy planning. The average scan time of the prostate was 30 s, and the average 3D reconstruction of the prostate took 3 s. We performed four motion scenarios: the phantom was scanned in a stationary state (S), with horizontal motion (H), with vertical motion (V), and with a combination of the two (C). System validation is performed by registering the prostate point cloud reconstructions acquired during different motions (H, V, C) with those obtained in the stationary state. ICP registration with a threshold of 0.8 mm yields mean 83.2\% fitness and 0.35 mm RMSE for S-H registration, 84.1\% fitness and 0.37 mm RMSE for S-V registration and 79.4\% fitness and 0.37 mm RMSE for S-C registration. Due to the elastic and soft material properties of the prostate phantom, the maximum robot tracking error was 3 mm, which can be sufficient for prostate biopsy according to medical literature. The maximum delay in motion compensation was 0.5 s.