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Soft Robotic Manipulator for Intra-operative MRI-guided Transoral Laser Microsurgery

A joint research team of engineers and clinicians from HKU and The Chinese University of Hong Kong (CUHK) has recently developed a soft robotic manipulator for magnetic resonance (MR) imaging (MRI)-guided transoral laser microsurgery (TLM). Dr. Ka-Wai Kwok and his research students Ge Fang, Marco Chun Kit Chow, Justin Di-lang Ho, Zhuoliang He, Kui Wang (Department of Mechanical Engineering, HKU) worked out the prototype with Dr. James Tsoi (Faculty of Dentistry, HKU), Dr. Jason Chan and Dr. Catherine Chan (Department of Otorhinolaryngology, CUHK). This innovation has recently been published in Science Robotics.

TLM uses a highly localized laser beam to enable precise tissue incision. It is a treatment of head and neck cancer (HNC), which is the seventh most common cancer in the world, causing more than 450,000 deaths every year. Laser ablation with ultranarrow margins has been shown to be effective for certain cancers, and can also be used even for bulky tumors in early stages, with the advantage of minimal thermal spread to the surrounding normal tissues. However, surgeons need to depend on their experience to approximate a safe “deep margin” of the ablation to avoid injury to crucial neurovascular or muscular structures. In prevailing surgical settings, intraoperative (intra-op) evaluation of during such treatment is time-consuming and costly.

MRI has gained prevalence as an intra-op image modality for its ability to contrast cancerous tissue as well as neurovascular structures. MR thermometry is also widely adopted for ablation guidance. MRI can form high resolution three-dimensional (3D) surgical roadmaps for pre-operative planning. By pairing anatomical and thermal imaging, MRI is the unique modality that can provide accurate intra-op monitoring of laser cutting/ ablation depth to protect critical structures, while ensuring adequate resection margins.

The team developed a soft robotic platform capable to leverage real-time intra-op MRI guidance together with continuous control of laser beam projection within the confined oral and pharyngeal cavities. The soft robot size is compact (⌀12mm x 100mm) and lightweight (~200g), while providing 5 degrees-of-freedom (DOFs). The robot integrates a lens-pigtailed laser fiber which enables endoscopic intervention through a patient-specific dental anchorage in the oral cavity. The laser manipulator incorporates hybrid soft and hard structures for laser steering with enhanced stiffness and lowered hysteresis. The hydraulic-actuated structure is rapidly fabricated with MR-safe materials and thus generates zero electromagnetic (EM) interference with MRI. Ex vivo tissue alation and a cadaveric head-and-neck trial have been carried out to validate feasibility of the proposed system.

Enhanced surgical outcomes such as function preservation and reduced need for further adjuvant therapy can result from intuitive and precise feedback of the ablation process to surgeons in combination with precise robot laser control. Dr. Ka-Wai Kwok and the team will further work on miniaturizing the robot size to access more confined sites like the nasal and sinus cavity. His team will also work on implementing specific image sequences for faster feedback of images to the robot system.

Acknowledgement to research team:

  • Dr. Ka-Wai Kwok, Ge Fang, Marco Chun Kit Chow, Justin Di-lang Ho, Zhuoliang He, Kui Wang, Department of Mechanical Engineering, HKU

  • Dr. T.C. Ng, Dr. James Kit Hon Tsoi, Faculty of Dentistry, HKU

  • Dr. Hing Chiu Chang, Department of Diagnostic Radiology, HKU

  • Dr. Jason Ying Kuen Chan, Dr. Po Ling Chan, Department of Otorhinolaryngology, Head and Neck Surgery, CUHK

  • Dr. Danny Tat Ming Chan, Division of Neurosurgery, Prince of Wales Hospital

  • Prof. Yunhui Liu, Department of Mechanical and Automation Engineering, CUHK

  • Dr. Floyd Christopher Holsinger, Head & Neck Surgery, Stanford University Medical Cente

Details of publication:

G. Fang, M.C.K. Chow, J.D.L. Ho, Z. He, K. Wang, T.C. Ng, J.K.H. Tsoi, P.L. Chan, H.C. Chang, D.T.M. Chan, C. Holsinger, J.Y.K. Chan, K.W Kwok, “Soft Robotic Manipulator for Intra-operative MRI-guided Transoral Laser Microsurgery”, Science Robotics, 6(57), 2021 DOI: 10.1126/scirobotics.abg5575

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