Steady-Hand Eye Robot 3.0: Optimization and Benchtop Evaluation for Subretinal Injection.

Subretinal injection methods and other procedures for treating retinal conditions and diseases (many considered incurable) have been limited in scope due to limited human motor control. This study demonstrates the next generation, cooperatively controlled Steady-Hand Eye Robot (SHER 3.0), a precise and intuitive-to-use robotic platform achieving clinical standards for targeting accuracy and resolution for subretinal injections. The system design and basic kinematics are reported and a deflection model for the incorporated delta stage and validation experiments are presented. This model optimizes the delta stage parameters, maximizing the global conditioning index and minimizing torsional compliance. Five tests measuring accuracy, repeatability, and deflection show the optimized stage design achieves a tip accuracy of < 30 µm, tip repeatability of 9.3 µm and 0.02°, and deflections between 20-350 µm/N. Future work will use updated control models to refine tip positioning outcomes and will be tested on in vivo animal models.

Delta Robot Kinematic Calibration for Precise Robot-Assisted Retinal Surgery.

High precision is required for ophthalmic robotic systems. This paper presents the kinematic calibration for the delta robot which is part of the next generation of Steady-Hand Eye Robot (SHER). A linear error model is derived based on geometric error parameters. Two experiments with different ranges of workspace are conducted with laser sensors measuring displacement. The error parameters are identified and applied in the kinematics to compensate for modeling error. To achieve better accuracy, Bernstein polynomials are adopted to fit the error residuals after compensation. After the kinematic calibration process, the error residuals of the delta robot are reduced to satisfy the clinical requirements.

Force and Velocity Based Puncture Detection in Robot Assisted Retinal Vein Cannulation: In-Vivo Study.

OBJECTIVE: Retinal vein cannulation is a technically demanding surgical procedure and its feasibility may rely on using advanced surgical robots equipped with force-sensing microneedles. Reliable detection of the moment of venous puncture is important, to either alert or prevent the clinician from double puncturing the vessel and damaging the retinal surface beneath. This paper reports the first in-vivo retinal vein cannulation trial on rabbit eyes, using sensorized metal needles, and investigates puncture detection. METHODS: We utilized total of four indices including two previously demonstrated ones and two new indices, based on the velocity and force of the needle tip and the correlation between the needle-tissue and tool-sclera interaction forces. We also studied the effect of detection timespan on the performance of detecting actual punctures. RESULTS: The new indices, when used in conjunction with the previous algorithm, improved the detection rate form 75% to 92%, but slightly increased the number of false detections from 37 to 43. Increasing the detection window improved the detection performance, at the cost of adding to the delay. CONCLUSION: The current algorithm can supplement the surgeons' visual feedback and surgical judgment. To achieve automatic puncture detection, more measurements and further analysis are required. Subsequent in-vivo studies in other animals, such as pigs with their more human like eye anatomy, are required, before clinical trials. SIGNIFICANCE: The study provides promising results and the criteria developed may serve as guidelines for further investigation into puncture detection in in-vivo retinal vein cannulation.

Towards a Clinically Optimized Tilt Mechanism for Bilateral Micromanipulation with Steady-Hand Eye Robot.

Cooperative robotic systems for vitreoretinal surgery can enable novel surgical approaches by allowing the surgeon to perform procedures with enhanced stabilization and high accuracy tool movements. This paper presents the optimization and design of a four-bar linkage type tilt mechanism for a novel Steady-Hand Eye Robot (SHER) which can be used equivalently on both, the left and right patient side, during a bilateral approach with two robots. In this optimization, it is desirable to limit the workspace needed for compensation motions that ensure a virtual remote center of motion (V-RCM). The safety space around the patient, the space for the surgeon's hand and maintaining positional accuracy are also included in the optimization. The applicability of the resulting optimized mechanism was confirmed with a design prototype in a representative mock-up of the surgical setting allowing multiple directions of robot approach towards a medical phantom.

A minimally invasive robotic surgery approach to perform totally endoscopic coronary artery bypass on beating hearts.

The currently available robotic systems rely on rigid heart stabilizers to perform totally endoscopic coronary artery bypass (TECAB) surgery on beating hearts. Although such stabilizers facilitate the anastomosis procedure by immobilizing the heart and holding the surgery site steady, they can cause damage to the heart tissue and rupture of the capillary vessels, due to applying relatively large pressures on the epicardium. In this paper, we propose an advanced robotic approach to perform TECAB on a beating heart with minimal invasiveness. The idea comes from the fact that the main pulsations of the heart occur as excursions in normal direction, i.e., perpendicular to the heart surface. We devise a 1-DOF flexible heart stabilizer which eliminates the lateral movements of the heart, and a 1-DOF compensator mechanism which follows the heart trajectory in the normal direction, thus canceling the relative motion between the surgical tool and the heart surface. In fact, we bring a compromise between two radical approaches of operating on a completely immobilized beating heart with no heart motion compensation, and operating on a freely beating heart with full compensation of heart motion, considering the invasiveness of the first and the technical challenges of the second approach. We propose operating on a partially stabilized beating heart with unidirectional compensation of the heart motion; the flexible stabilizer would exert much less holding force to the heart tissue and the robotic system with unidirectional compensator would be technically feasible. In the proposed approach, a motion sensor mounted on the stabilizer measures the heart excursion data and sends it into a control unit. A predictive controller uses this data to generate an automated trajectory. The slave robots follow this trajectory, which is superimposed on the surgeon's tele-operation commands received from a master console. Finally, the tool-activation units in the slave robots actuate the articulated laparoscopic tools to perform the anastomosis procedure. The evaluation of the hypothesis showed that our solution for the robotic TECAB on beating heart is both practical and cost effective. We showed in an in-vivo study that the flexible stabilizer can effectively restrict the heart lateral movements, while allowing for its normal excursion. We found readily available linear motors which could afford the high forces, speeds and accelerations required for following the heart trajectory. Finally, we showed that the tool-activation unit is capable of providing the maneuverability and workspace required for the most challenging task of CABG procedure, i.e., anastomosis suturing.

Design of a 4 DOF laparoscopic surgery robot for manipulation of large organs.

In this paper, a 4-DOF robotic arm for tool handling in laparoscopic surgery is introduced. The robot provides sufficient force to handle endoscopic tools used for large organ manipulation and is capable of measuring the tool-tissue forces. The RCM constraint is achieved using a spherical mechanism and roll and insertion motions are provided using time pulley and spindle-drive, respectively. The forward and inverse kinematics of the robot was solved and the dimensions of its links were determined, using particle swarm optimization method, so that the maximum kinematic and dynamic performance could be achieved.