Tools Highlight B: Image-Guided Intra-Cavity Robots for Prostate Interventions

With an annual incidence of 221,000 and 33,000 deaths, prostate cancer is the most common and deadliest form



of cancer in men. In the U.S. alone, each year over 1,000,000 prostate biopsies are performed. About 20% of these men are diagnosed with cancer, while the rest will suffer from benign prostate hyperplasia that typically requires surgical intervention at some point too. Contemporary image-guided prostate interventions are constrained to free-hand techniques under ultrasound (US) guidance. Although US is overwhelmingly popular due to its realtime nature, safety, and low cost, in some respect it has suboptimal quality and the freehand intervention technique is also not adequate. We pursue research to eliminate both of these shortcomings. Our ERC is developing novel MRI and US guided needle placement medical robot systems to redefine the standard of care in prostate interventions. These robots utilize the safest and shortest access route to the site of disease trough the rectal cavity. There are formidable technological




challenges to overcome. First there is no room to maneuver in the cavity, where the surgical needle must “turn a corner” to enter the prostate gland across the wall of the cavity. The second barrier is compatibility with the given imaging device.

Magnetic Resonance Imaging (MRI) provides the best anatomical picture available today, but the high magnetic field (200,000 times stronger than the Earth’s) excludes the use of metals and electronics inside the scanner where the workspace is also strictly limited. Due to these constraints, such high-quality scanners were previously unavailable for surgical interventions. Our MRI-guided robot (see figure above) overcomes these problems and it enables precise anatomical targeting inside a closed high-field MRI scanner, with previously unprecedented intra-procedural image quality. The system is in multiple clinical trials for prostate biopsy and seed placement, lead by Dr. Cynthia Menard at NIH. Clinical accuracy has been promising, based on early results in both phase-1 trials. We have encountered no complications and safety problems, both during and after the procedures.

Transrectal ultrasound (TRUS) is the most popular prostate imaging tool, yet the imager entirely occupies the rectal cavity, thus leaving no room for mechanical actuation of any kind. We built a robot (see figure above) to overcome this problem by navigating a pair of flexible surgical needles in a ~2 mm space between a commercial off-the-shelf TRUS probe and the cavity wall, while keeping all actuation gear and mechatronic elements outside the patient’s body. Initial phantom experiments suggest that targeting and needle placement accuracies are better than achieved manually. The prototype device is being adopted for ultrasonic ablation of recurrent prostate cancer, which is a novel therapeutic procedure that is impossible to perform manually. This work is in partnership with Acoustic MedSystems, Inc., financed from a phase-1/phase-2 STTR grant from NIH.

Further information is available at http://www.cisst.org/~gabor/APT-MR.htm and http://www.cisst.org/~gabor/TRUAP.htm


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