MRI-Guided Multi-Stage Robotic Positioner Enhances Stereotactic Neurosurgery Precision

Magnetic resonance imaging (MRI) offers significant benefits in neurosurgery, providing detailed 3D visualizations of neurovascular structures and tumors. Traditionally, its use has been restricted to analyzing static images taken before or after surgery, leading to potential inaccuracies due to the setup of stereotactic frames, image registration, and brain shifts. Researchers have now developed a specialized interactive multi-stage robotic positioner for use in MRI-guided stereotactic neurosurgery, enhancing the precision of these surgical interventions.

This advanced system developed by a team from the University of Hong Kong (HKU, Pokfulam, Hong Kong) is designed to assist in various procedures such as cannula or needle targeting, which are crucial in treatments like deep brain stimulation (DBS) for movement disorders including Parkinson’s disease. Additionally, it supports a variety of therapeutic interventions like biopsy, drug delivery, ablation, and catheter placement into deep brain areas. In 2018, this team successfully developed the world’s first robotic system capable of conducting bilateral stereotactic neurosurgery within an MRI setting, which helped overcome challenges associated with lengthy procedures and complex workflows. The initial prototype has since been refined by the team.

Image: The interactive multi-stage robotic positioner is specifically designed for MRI-guided stereotactic neurosurgery (Photo courtesy of University of Hong Kong)

The latest version of this system facilitates interactive, semi-automatic manipulation in two stages. Initially, based on pre-operative images, the surgeon positions the robotic instrument guide towards the target trajectory. The system incorporates fiber-optic lighting to visually indicate any angulation errors relative to the target trajectory. When the instrument guide is aligned within 5 degrees of the target, it can be remotely locked in place. The system uses finite element analysis (FEA) for design optimization and employs a fluid-driven soft actuator architecture to position the instrument with an orientation error of less than 0.2 degrees. Orientation locking is robust, utilizing soft robotic mechanisms such as tendon-driven baking units and granular jamming.

Following this setup, the surgeon manually inserts the instrument through the robot-guided pathway, with an insertion stopper aiding in setting the precise depth. This technology helps eliminate the inherent errors found in traditional frame-based stereotaxy, thus enhancing insertion accuracy and improving surgical outcomes. It also reduces the duration of the operation, which contributes to greater patient comfort and satisfaction. The device itself is compact and lightweight (97 x 81 mm, 203g), designed to be compatible with most standard imaging head coils. It includes custom-made miniature wireless omnidirectional tracking markers and a zero-electromagnetic-interference system to support accurate robot registration under real-time MRI conditions. The system's effectiveness has been confirmed through cadaveric studies and skull model testing, achieving a precision error of less than 3 mm and showing significant potential for future clinical application.

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