Computed Tomography (CT) guided procedures are common minimally invasive technique used to perform diagnostic and therapeutic procedures. These applications include obtaining biopsy samples, delivering medications, aspiring/draining fluids, and ablating regions of interest. This minimally invasive approach is especially common in pediatrics. Approximately five to nine million children receive CTs each year. Despite the excellent boney region discrimination and high resolution possible with CT, there are concerns regarding the risks of ionizing radiation exposure. Exposure is often minimized, as CT exposure in children has been linked to the development cancer in the future.
In this paper we introduce a novel and enabling MRI-compatible needle guidance toolkit intended to streamline arthrography procedures, eliminating the need for ionizing radiation exposure during this diagnostic procedure. We developed a flexible 2D grid template with unique patterns in which each point on the grid can be uniquely represented and denoted with respect to surrounding patterns. This MRI-visible non-repeating grid template sits on top of the patient’s skin in the region of interest and allows the radiologist to visualize the skin surface in the MR images and correlates each point in MR image with the corresponding point on the grid. In this manner, the radiologist can intuitively find the entry point on the skin according to their plan. An MRI-compatible handheld positioning device consisting of a needle guide, two baseline bubble inclinometers, and an MRI-compatible stabilizer arm allows the radiologist to adjust the orientation of the needle in two directions. The radiologist selects an entry point on MR images, identifies a grid location through which the needle would be projected to pass on the image, and then reproduces this needle position and angulation using the MRI-compatible handheld device and the physical grid. To evaluate the accuracy of needle targeting with the MRI-compatible needle guidance toolkit, we used the kit to target 10 locations in a phantom in a Philips Achieva 1.5T MRI. The average targeting error was 2.2±0.7 mm. Average targeting procedure time was around 20 minutes for each target.
Here we report on a phantom targeting study for accuracy evaluation of our body-mounted robot for Magnetic Resonance Imaging (MRI) guided arthrography. We use a standardized method developed in a multi-institute effort with the aim of providing an objective method for accuracy and signal-to-noise Ratio (SNR) evaluation of MRI-compatible robots. The medical definition of arthrography is the radiographic visualization of a joint (as the hip or shoulder) after the injection of a radiopaque substance. That procedure provides an evaluation of the joints using two medical imaging modalities, fluoroscopic x-ray imaging and MRI. Conventional arthrography is done in two stages: first the contrast dye injected into the joint (fluoroscopic procedure) and then an MRI to evaluate the joint space. Our MRI-guided compatible robot is intended to enable needle placement in the MRI environment, streamlining the procedure. The targeting study was conducted using the quality assessment mockup phantom and associated software called QARAI that was developed by the URobotics Laboratory at Johns Hopkins and colleagues. The mockup contains four embedded fiducials and an 8 by 8 grid which is used to automatically identify the targeting points with high accuracy. The study was conducted on a Philips Achieva 1.5T MRI system and 10 points were targeted. All targets were reached with an average error of 2.71mm. The targeting algorithm, as well as the control of the robot, were completed using robot control modules developed with the open source software 3D Slicer.
Shoulder arthrography is a diagnostic procedure which involves injecting a contrast agent into the joint space for enhanced visualization of anatomical structures. Typically, a contrast agent is injected under fluoroscopy or computed tomography (CT) guidance, resulting in exposure to ionizing radiation, which should be avoided especially in pediatric patients. The patient then waits for the next available magnetic resonance imaging (MRI) slot for obtaining high-resolution anatomical images for diagnosis, which can result in long procedure times. Performing the contrast agent injection under MRI guidance could overcome both these issues. However, it comes with the challenges of the MRI environment including high magnetic field strength, limited ergonomic patient access, and lack of real-time needle guidance. We present the development of an integrated robotic system to perform shoulder arthrography procedures under intraoperative MRI guidance, eliminating fluoroscopy/CT guidance and patient transportation from the fluoroscopy/CT room to the MRI suite. The average accuracy of the robotic manipulator in benchtop experiments is 0.90 mm and 1.04 deg, whereas the average accuracy of the integrated system in MRI phantom experiments is 1.92 mm and 1.28 deg at the needle tip. Based on the American Society for Testing and Materials (ASTM) tests performed, the system is classified as MR conditional.
We present our latest work on designing a magnetically anchored wireless stereoscopic robot with 2 degrees of freedom (DOF) Pan-Tilt unit for single-port minimally invasive surgery (MIS). This camera could reduce the tool clashing issue in MIS and could provide better angulation and visualization of surgical field. After introduction of the robot through umbilicus (belly button), it is anchored to internal abdominal wall using a magnet from outside. Surgeon can change view angle of the camera remotely via a wireless joystick and a real-time stereo view will be displayed on a user interface screen. Since the robot is anchored using an external magnet on the abdominal wall during the surgical operation, surplus shocks and slight tremble of the robot will result in poor visualization. Therefore, we developed a real-time video stabilization scheme to eliminate these affects. Our proposed method uses a high frequency inertial measurement sensory data fused with visual optical flow vectors, extracted from the stereo camera, to estimate the unwanted shocks during the video streaming. This method compensates and stabilizes video streams in real-time by shifting the video images in the opposite direction of the estimated motion vector. We conducted several experiments including robot control, video streaming performance, and real-time video stabilization to investigate the system function. The results of these experiments are reported in this paper.
In this paper we report development of an integrated RF coil for our body-mounted arthrography robot called Arthrobot. Arthrography is the evaluation of joint conditions using imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI). Current arthrography practice requires two separate stages; an intra-articular contrast injection guided by fluoroscopy or ultrasound followed by MR imaging. Our body-mounted robot is intended to enable needle placement in the MRI environment, streamlining the procedure. To improve imaging with our robot, a single loop coil was created and embedded into the mounting adaptor of the robot. This coil provides enough spatial coverage and sensitivity to localize anatomical points of interest and registration fiducials on the robot frame. In this paper we report the results of a SNR and heating study using our custom-made RF coil in four different scenarios using T1 and T2 weighted MR images: 1) no robot present, 2) robot off, 3) robot powered on, and 4) robot running. We also report an end-to-end robotic-assisted targeting study in a Philips MRI scanner suite using Arthrobot and our custommade RF coil for image acquisition. The SNR results and targeting results were promising. SNR dropped 32% for T1 weighted images compared to baseline (no robot present) images. For T2 weighted images the SNR drop was 42%. The average targeting error was 2.91 mm with a standard deviation (SD) of 1.82 mm. In future work we plan to replace the passive fiducials embedded in the base of Arthrobot with active fiducials that are tracked by the MRI system. These active fiducials will enable real-time tracking of the robot base and could allow breathing motion compensation during robotic procedures.
In brain tumor ablation procedures, imaging for path planning and tumor ablation are performed in two different sessions. Using pre-operative MR images, the neurosurgeon determines an optimal ablation path to maximize tumor ablation in a single path ablation while avoiding critical structures in the brain. After pre-operative path planning the patient undergoes brain surgery. Manual planning for brain tumor ablation is time-intensive. In addition, the preoperative images may not precisely match the intra-operative images due to brain shift after opening the skull. Surgeons sometimes therefore adjust the path planned during the surgery, which leads to increased anaesthesia and operation time. In this paper, a new heuristic-based search algorithm is introduced to find an optimal ablation path for brain tumors, that can be used both pre- and intra-operatively. The algorithm is intended to maximize the safe ablation region with a single path ablation. Given the tumor location, healthy tissue locations, and a random start point on the skull from medical images, our proposed algorithm computes all plausible entry points on the skull and then searches for different ablation paths that intersect with the tumor, avoids the critical structures, and finds the optimal path. We implemented Breadth First Search (BFS), Dijkstra, and our proposed heuristic based algorithms. In this paper we report the results of a comparative study for these methods in terms of the search space explored and required computation time to find an optimal ablation path.
We have developed a mechanical horseback riding simulator for the rehabilitation of children with neurological and musculoskeletal disabilities, focused on improving trunk control in this population. While overseen by a physical or occupational therapist, the movement of a horse is often used as therapy for these patients (hippotherapy). However, many children never have the chance to experience hippotherapy due to geographical and financial constraints. We therefore developed a horseback riding simulator that could be used in the office setting to make hippotherapy more accessible for our patient population. The system includes a motion platform, carousel horse, and tracking system. We developed a virtual reality display which simulates a horse moving along a pier. As the horse moves forward, other horses come toward it, and the patient must lean left or right to move out of the way. The tracking system provides the position of tracking markers which are placed on the patient’s back, and this information is used to control the motion of the horse. Under an Institutional Review Board (IRB) approved trial, we have enrolled two patients with cerebral palsy to date. This was after completing testing on five healthy pediatric volunteers as required by the IRB. Early results show the feasibility of the system.
We have developed a three degree of freedom robot with a custom designed video game for ankle rehabilitation of children with cerebral palsy and other neuromuscular disorders. Physical therapy is commonly used to stretch and strengthen these patients, but current treatment methods have some limitations. By developing a robotic device and associated airplane video game, we aim to improve ankle range of motion, muscle strength, and motor control in a quantitative manner that is also fun and motivating for the child. Our PedBot robot consists of three intersecting axes with a remote center of motion in the ankle joint area. The patient’s ankle is strapped to PedBot and becomes a controller for the airplane game. The patient flies the plane through a series of rings and a bell sound is made each time the plane successfully passes through the center of a ring. To date we enrolled 4 children ages 4-11 in an IRB approved trial. The children completed up to 5 sessions. All of the children said they enjoyed the therapy. A 4-year old boy who completed all five sessions showed measureable improvements in several degrees of motion. We have also begun EMG based studies to investigate muscle activity during robotic rehabilitation.
Ureteroscopy is a minimally invasive procedure for diagnosis and treatment of urinary tract pathology. Ergonomic and visualization challenges as well as radiation exposure are limitations to conventional ureteroscopy. Therefore, we have developed a robotic system to “power drive” a flexible ureteroscope with 3D tip tracking and pre-operative image overlay. The proposed system was evaluated using a kidney phantom registered to pre-operative MR images. Initial experiments show the potential of the device to provide additional assistance, precision, and guidance during urology procedures.
Cochlear implantation is the standard of care for infants born with severe hearing loss. Current guidelines approve the surgical placement of implants as early as 12 months of age. Implantation at a younger age poses a greater surgical challenge since the underdeveloped mastoid tip, along with thin calvarial bone, creates less room for surgical navigation and can result in increased surgical risk. We have been developing a temporal bone dissection simulator based on actual clinical cases for training otolaryngology fellows in this delicate procedure. The simulator system is based on pre-procedure CT (Computed Tomography) images from pediatric infant cases (<12 months old) at our hospital. The simulator includes: (1) simulation engine to provide the virtual reality of the temporal bone surgery environment, (2) a newly developed haptic interface for holding the surgical drill, (3) an Oculus Rift to provide a microscopic-like view of the temporal bone surgery, and (4) user interface to interact with the simulator through the Oculus Rift and the haptic device. To evaluate the system, we have collected 10 representative CT data sets and segmented the key structures: cochlea, round window, facial nerve, and ossicles. The simulator will present these key structures to the user and warn the user if needed by continuously calculating the distances between the tip of surgical drill and the key structures.
During prostate needle insertion, the gland rotates and displaces resulting in needle placement inaccuracy. To compensate for this error, we proposed master-slave needle steering under real-time MRI in a previous study. For MRI-compatibility and accurate motion control, the master (and the slave) robot uses piezo actuators. These actuators
however, are non-backdrivable. To cope with this issue, force sensor is required. Force sensor is also required at the slave side to reflect the insertion force to clinician’s hand through the master robot. Currently, there is no MRI-compatible force sensor commercially available. In order to generate a combination of linear and rotary motions for needle steering, this study is seeking to develop a MRI-compatible 2 Degrees of Freedom (DOF) force/torque sensor. Fiber Brag Grating (FBG) strain measuring sensors which are proven to be MRI-compatible are used. The active element is made of phosphor-bronze and other parts are made of brass. The force and torque measurements are designed to be entirely decoupled. The sensor measures -20 to 20 N axial force with 0.1 N resolution, and -200 to 200 Nmm axial torque with 1 Nmm resolution. Analytical and Finite Element (FE) analyses are performed to ensure the strains are within the measurable range of the FBG sensors. The sensor is designed to be compact (diameter =15 mm, height =20 mm) and easy to handle and install. The proposed sensor is fabricated and calibrated using a commercial force/torque sensor.
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