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Interactive Multi-Stage Robotic Positioner for Intra-Operative MRI-Guided Stereotactic Neurosurgery

A research team led by Dr. Ka-Wai Kwok at the Department of Mechanical Engineering of the University of Hong Kong (HKU) has developed an interactive multi-stage robotic positioner for stereotactic neurosurgery, guided by intra-operative magnetic resonance (MR) imaging (MRI).


The team proposed an interactive multi-stage robotic positioner for cannula/ needle instruments used in stereotactic neurosurgeries, with the goal to provide more accurate and effective treatment of many neurological diseases such as brain tumors and Parkinson’s disease. The system was validated through cadaveric studies and skull model testing, forming a foundation for future clinical studies. Initial results have just been published in the international journal Advanced Science.


This is a collaborative achievement by a multi-disciplinary team including engineering and clinical experts from esteemed research institutions: Prince of Wales Hospital (PWH), The Chinese University of Hong Kong (CUHK), University College London (UCL), and Johns Hopkins University (JHU). The team’s combined perspectives and technical prowess allowed them to tackle the prevailing challenges faced.


Features of the proposed robotic system

The robotic positioner is proposed by the team to assist the surgeon in performing intra-op MRI-guided stereotactic neurosurgeries, in particular interventions involved those cannula/needle targeting, such as biopsy, injection, ablation, catheter placement, and deep brain stimulation (DBS).


The robot is lightweight (203 g) and compact (Ø97 × 81 mm), allowing its skull-mounted structure that fits within most standard imaging head coils. Rather than operating in a fully autonomous manner, the system is used in two stages, including wide-range workspace positioning provided by the surgeon’s manual manipulation, followed by soft robotic fine adjustment to precisely aim towards the target tissue in the brain:




Stage 1) Manual coarse adjustment performed interactively by surgeon


Initially, the surgeon orients robot instrument guide towards the direction of the planned trajectory based on pre-operative images. In-built fiber-optic lighting of the system intuitively indicates the angulation error with reference to the planned trajectory. Once the surgeon has oriented the instrument guide close to the planned trajectory with error < 5°, the system will be remotely locked.


Stage 2) Automatic fine adjustment with precise, responsive, and high-resolution soft robotic positioning


The system then automatically positions the instrument guide to the planned trajectory. Making use of finite element analysis (FEA)- based design and optimization of the fluid-driven soft actuator architecture, the instrument could be positioned accurately with <0.2° orientation error.


Across the stages, robust orientation locking is achieved through soft robotic mechanisms like tendon-driven braking units and granular jamming. Instrument insertion depth is set with the assistance of a stopper. The surgeon then manually inserts the instrument via the robot instrument guide for biopsy, injection, etc. Subsequent MRI can be performed to monitor the procedure, e.g. MR thermal imaging for ablation evaluation.


In this work, the team also proposed a custom-made miniature wireless omni-directional tracking markers that facilitated robot registration under MRI, achieving suitable targeting accuracy in cadaveric studies. The system is fabricated with MR-safe materials, generating zero electromagnetic interference, allowing the use of intra-op MRI guidance during robot actuation and for evaluating the interventional process.


The proposed system has gone through skull model and cadaver trials to validate its clinical workflow and feasibility in human anatomy. The results showed that the robot achieved precision with <3 mm error. The prototype is IP-protected with a patent application.


Related publication:

Z. He, J. Dai, J.D.L. Ho, H.S. Tong, X. Wang, G. Fang, L. Liang, C.L. Cheung, Z. Guo, H.C. Chang, I. Iordachita, R.H. Taylor, W.S. Poon, D.T.M. Chan, K.W. Kwok, “Interactive Multi-stage Robotic Positioner for Intra-operative MRI-guided Stereotactic Neurosurgery,” Advanced Science, 2305495, 2023

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