Journal of Medical Robotics Research

We present a telemanipulation system for retinal surgery that uses a full range of unmodified commercially available instruments. The system is compact and light enough that it could reasonably be made head-mounted to passively compensate for head movements. Two mechanisms are presented that enable the system to use commercial actuated instruments, and an instrument adapter enables quick-change of instruments during surgery. A custom stylus for a haptic interface enables intuitive and ergonomic telemanipulation of actuated instruments. Experimental results with a force-sensitive phantom eye show that telemanipulated surgery results in reduced forces on the retina compared to manual surgery, and training with the system results in improved performance.

Surgeons can benefit from the cooperation with a robotic assistant during the repetitive execution of precise targeting tasks on soft tissues, such as brain cortex stimulation procedures in open-skull neurosurgery. Position-based force-to-motion control schemes may not be satisfactory solution to provide the manipulator with the high compliance desirable during guidance along wide trajectories. A new torque controller with nonlinear force feedback enhancement (FFE) is presented to provide augmented haptic perception to the operator from instrument-tissue interaction. Simulation tests were performed to evaluate the system stability according to different nonlinear force modulation functions (power, sigmoidal and arc tangent). The FFE controller with power modulation was experimentally validated with a pool of nonexpert users using brain-mimicking gelatin phantoms (8–16% concentration). Besides providing hand tremor rejection for a stable holding of the tool, the FFE controller was proven to allow for a safer tissue contact with respect to both robotic assistance without force feedback and freehand executions (50% and 75% reduction of the indentation depth, respectively). Future work will address the evaluation of the safety features of the FFE controller with expert surgeons on a realistic brain phantom, also accounting for unpredictable tissue motions as during seizures due to cortex stimulation.

In the past two decades, several instruments have been developed to overcome the loss of haptic sensation in minimally invasive surgery (MIS). Unfortunately, none of the proposed instruments has been clinically adopted or utilized in natural orifice translumenal endoscopic surgery (NOTES) procedures. The challenge is that NOTES instruments require mounting upon flexible endoscopes thus altering endoscope flexibility and dexterity. We have developed a novel wireless tissue stiffness probe (WTSP) that can be used with a flexible endoscope and create a real-time stiffness distribution map with potential to restore haptic sensation in NOTES. The aim of our study was to assess the performance and feasibility of the WTSP in an ex vivo trial (three phantom models of different elasticity; comparing discrimination of human touch with the WTSP) and in an in vivo trans-colonic access NOTES procedure. Overall, the WTSP was able to detect the stiffness of the three phantoms with a relative error smaller than 3% and a success rate of 100% versus 95% when compared to human perception. The novel WTSP was successful in providing the operator with tactile and kinesthetic feedback for accurate discrimination between tissue phantoms. In vivo tissue palpation was feasible using the WTSP in a trans-colonic NOTES procedure. The WTSP did not encumber the maneuverability or dexterity of the flexible endoscope. This innovative approach to tissue palpation has the potential to open a new paradigm in the field of NOTES where no mechanical link between the external platform and the target region exists.

To improve lung tumor conspicuity during CT-guided cryoablations, we used nonrigid image registrations to fuse pre-procedural MR images and intra-procedural CT images and determined which set of CT images taken at planning, targeting, and monitoring phases of the procedure provided the most accurate and fastest registrations. In 10 percutaneous CT-guided cryoablation procedures, MR images were registered with intra-procedural CT images using a nonrigid registration technique using an intensity-based approach with affine and B-Spline transformations. The time to complete the registration as well as the accuracy of the registration defined by Target Registration Error (TRE), Dice Similarity Coefficient (DSC), and Hausdorff Distance (HD) were measured to assess the performance of the registration. The least significant difference (LSD) method was used as a post-hoc analysis for comparing time and accuracy among planning, targeting, and monitoring phases. The mean TRE of the registration ranged from 6.26 (planning) to 10.31 (monitoring) mm. The mean DSC ranged from 83.86 (monitoring) to 89.22 (planning). The mean HD values ranged from 7.74 (targeting) to 12.20 (monitoring). Mean registration time ranged from 68.67 (monitoring) to 92.02 (planning) s. Using HD, registrations in either the planning or targeting phase were more accurate than in the monitoring phase. The registration was faster using monitoring images than using planning images. Nonrigid registration techniques can be used to fuse pre-procedural MR images with intra-procedural CT images with varying performance depending on the CT images taken at the different phases of the procedure. Therefore, caution should be taken in setting expectations on accuracies and speeds of registration depending on the phases of the CT-guided ablation procedures.