Ronnie Wong

30 Years of Neurosurgical Robots: Review and Trends for Manipulators and Associated Navigational Systems.

This review provides an examination of contemporary neurosurgical robots and the developments that led to them. Improvements in localization, microsurgery and minimally invasive surgery have made robotic neurosurgery viable, as seen by the success of platforms such as the CyberKnife and neuromate. Neurosurgical robots can now perform specific surgical tasks such as skull-base drilling and craniotomies, as well as pedicle screw and cochlear electrode insertions. Growth trends in neurosurgical robotics are likely to continue but may be tempered by concerns over recent surgical robot recalls, commercially-driven surgeon training, and studies that show operational costs for surgical robotic procedures are often higher than traditional surgical methods. We point out that addressing performance issues related to navigation-related registration is an active area of research and will aid in improving overall robot neurosurgery performance and associated costs.

Evaluation of flow velocities after carotid artery stenting through split spectrum Doppler optical coherence tomography and computational fluid dynamics modeling

Hemodynamics plays a critical role in the development of atherosclerosis, specifically in regions of curved vasculature such as bifurcations exhibiting irregular blood flow profiles. Carotid atherosclerotic disease can be intervened by stent implantation, but this may result in greater alterations to local blood flow and consequently further complications. This study demonstrates the use of a variant of Doppler optical coherence tomography (DOCT) known as split spectrum DOCT (ssDOCT) to evaluate hemodynamic patterns both before and after stent implantation in the bifurcation junction in the internal carotid artery (ICA). Computational fluid dynamics (CFD) models were constructed to simulate blood velocity profiles and compared to the findings achieved through ssDOCT images. Both methods demonstrated noticeable alterations in hemodynamic patterns following stent implantation, with features such as slow velocity regions at the neck of the bifurcation and recirculation zones at the stent struts. Strong correlation between CFD models and ssDOCT images demonstrate the potential of ssDOCT imaging in the optimization of stent implantation in the clinical setting.

Pulsed and CW adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser system for surgical laser soft tissue ablation applications

A surgical laser soft tissue ablation system based on an adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser operating in pulsed or CW mode with nitrogen assistance is demonstrated. Ex vivo ablation on soft tissue targets such as muscle (chicken breast) and spinal cord (porcine) with intact dura are performed at different ablation conditions to examine the relationship between the system parameters and ablation outcomes. The maximum laser average power is 14.4 W, and its maximum peak power is 133.1 W with 21.3 μJ pulse energy. The maximum CW power density is 2.33 × 106 W/cm2 and the maximum pulsed peak power density is 2.16 × 107 W/cm2. The system parameters examined include the average laser power in CW or pulsed operation mode, gain-switching frequency, total ablation exposure time, and the input gas flow rate. The ablation effects were measured by microscopy and optical coherence tomography (OCT) to evaluate the ablation depth, superficial heat-affected zone diameter (HAZD) and charring diameter (CD). Our results conclude that the system parameters can be tailored to meet different clinical requirements such as ablation for soft tissue cutting or thermal coagulation for future applications of hemostasis.

Development of an integrated optical coherence tomography-gas nozzle system for surgical laser ablation applications: preliminary findings of in situ spinal cord deformation due to gas flow effects

Gas assisted laser machining of materials is a common practice in the manufacturing industry. Advantages in using gas assistance include reducing the likelihood of flare-ups in flammable materials and clearing away ablated material in the cutting path. Current surgical procedures and research do not take advantage of this and in the case for resecting osseous tissue, gas assisted ablation can help minimize charring and clear away debris from the surgical site. In the context of neurosurgery, the objective is to cut through osseous tissue without damaging the underlying neural structures. Different inert gas flow rates used in laser machining could cause deformations in compliant materials. Complications may arise during surgical procedures if the dura and spinal cord are damaged by these deformations. We present preliminary spinal deformation findings for various gas flow rates by using optical coherence tomography to measure the depression depth at the site of gas delivery.

Regenerative effects in the Sit-to-Stand and Stand-to-Sit movement

While Sit-to-Stand and Stand-to-Sit are routine activities and are crucial pre-requisites to walking and running their underlying dynamics are poorly understood. Furthermore, the potential for using these movements to regenerate energy in energy-sensitive devices such as orthoses, prostheses and humanoid robots has never been examined. Insights in this domain can lead to more energy-efficient prosthesis, orthosis and humanoid robot designs. OBJECTIVES : The objectives are two-fold: first, to determine how much energy can be regenerated during standard movements related to transitions between sitting and standing on a scale humanoid model and second, to determine if the chosen actuator could produce better results if the gear ratio were modified. This manuscripts main contribution to the literature is by showing which joint provides the most regenerative effect during transitions between sitting and standing. MODEL DESIGN AND IMPLEMENTATION : Joint trajectories from existing biomechanics trials of sitting and standing transitions were fed into a 1/10 scale model of a humanoid robot. The robot model, developed in MapleSim, is comprised of standard and off-the-shelf subcomponents, including amplifier, NiMH battery and Robotis Dynamixel RX-28 actuators. RESULTS : Using the RX-28 actuator, the ankle, knee and hip joints all show a degree of regenerative effects, the hip demonstrates the most dramatic levels during the transition from standing to sitting. This contrasts with recent publications which show that the knee has the most important regenerative effects during walking and running. It is also found that for under 3 degree trajectory error the regenerative effect is best for all joints when the gear ratio is increased from the RX-28s 193:1 value to a value of approximately 760:1 for the ankle, 630:1 for the knee and 600:1 for the hip. CONCLUSIONS : During transitions between sitting and standing the greatest potential for regeneration occurs in the hips. Therefore, systems designed to implement regenerative effects between sitting and standing need to include subsystems at the hip for maximum regenerative effects.

Coaxial cavity injected OCT and fiber laser ablation system for real-time monitoring of ablative processes

This study presents the design of a system used to monitor laser ablation in real-time using Optical Coherence Tomography (OCT). The design of the system involves a high-powered fiber laser (wavelength of 1064nm, 1kW peak power) being built directly into the sample arm of the OCT system (center wavelength 1310). It is shown that the OCT laser light and subsequent backscatter pass relatively unaffected through the fiber laser. Initial results are presented showing monitoring of the ablation process at a single point in real time using m-mode imaging.

Assessment of hemodynamics of intracranial aneurysms using Doppler optical coherence tomography in patient specific phantoms: preliminary results (Conference Presentation)

Intracranial aneurysms affect a large number of individuals every year. Changes to hemodynamics are thought to be a crucial factor in the initial formation and enlargement of intracranial aneurysms. Previously, surgical clipping – an open an invasive procedure, was the standard of care. More recently, minimally invasive, catheter based therapies, specifically stenting and coiling, has been employed for treatment as it is less invasive and poses fewer overall risks. However, these treatments can further alter hemodynamic patterns of patients, affecting efficacy and prognosis. Doppler optical coherence tomography (DOCT) has shown to be useful for the evaluation of changes to hemodynamic patterns in various vascular pathologies, and intravascular DOCT may provide useful insight in the evaluation and changes to hemodynamic patterns before and during the treatment of aneurysms. In this study, we present preliminary results of DOCT imaging used in three patient-specific aneurysm phantoms located within the Circle of Willis both pre and post-treatment. These results are compared with computational fluid dynamics (CFD) simulations and high-speed camera imaging for further interpretation and validation of results.

Development of a low cost, 3-DOF desktop laser cutter using 3D printer hardware

This paper presents the development of a compact, desktop laser-cutting system capable of cutting materials such as wood, metal and plastic. A re-commissioned beheaded MakerBot® Replicator 2X is turned into a 3-DOF laser cutter by way of integration with 800W (peak power) fiber laser. Special attention is paid to tear-down, modification and integration of the objective lens in place of the print head. Example cuts in wood and metal will be presented, as well as design of an exhaust system.

Spinal cord deformation due to nozzle gas flow effects using optical coherence tomography

The use of gas assistance in laser machining hard materials is well established in manufacturing but not in the context of surgery. Laser cutting of osseous tissue in the context of neurosurgery can benefit from gas-assist but requires an understanding of flow and pressure effects to minimize neural tissue damage. In this study we acquire volumetric flow rates through a gas nozzle on the spinal cord, with dura and without dura.

Cadaveric in-situ testing of optical coherence tomography system-based skull base surgery guidance

Optical Coherence Tomography (OCT) has extensive potential for producing clinical impact in the field of neurological diseases. A neurosurgical OCT hand-held forward viewing probe in Bayonet shape has been developed. In this study, we test the feasibility of integrating this imaging probe with modern navigation technology for guidance and monitoring of skull base surgery. Cadaver heads were used to simulate relevant surgical approaches for treatment of sellar, parasellar and skull base pathology. A high-resolution 3D CT scan was performed on the cadaver head to provide baseline data for navigation. The cadaver head was mounted on existing 3- or 4-point fixation systems. Tracking markers were attached to the OCT probe and the surgeon-probe-OCT interface was calibrated. 2D OCT images were shown in real time together with the optical tracking images to the surgeon during surgery. The intraoperative video and multimodality imaging data set, consisting of real time OCT images, OCT probe location registered to neurosurgical navigation were assessed. The integration of intraoperative OCT imaging with navigation technology provides the surgeon with updated image information, which is important to deal with tissue shifts and deformations during surgery. Preliminary results demonstrate that the clinical neurosurgical navigation system can provide the hand held OCT probe gross anatomical localization. The near-histological imaging resolution of intraoperative OCT can improve the identification of microstructural/morphology differences. The OCT imaging data, combined with the neurosurgical navigation tracking has the potential to improve image interpretation, precision and accuracy of the therapeutic procedure.