Marcin Balicki

New steady-hand Eye Robot with micro-force sensing for vitreoretinal surgery

In retinal microsurgery, surgeons are required to perform micron scale maneuvers while safely applying forces to the retinal tissue that are below sensory perception. Real-time characterization and precise manipulation of this delicate tissue has thus far been hindered by human limits on tool control and the lack of a surgically compatible endpoint sensing instrument. Here we present the design of a new generation, cooperatively controlled microsurgery robot with a remote center-of-motion (RCM) mechanism and an integrated custom micro-force sensing surgical hook. Utilizing the forces measured by the end effector, we correct for tool deflections and implement a micro-force guided cooperative control algorithm to actively guide the operator. Preliminary experiments have been carried out to test our new control methods on raw chicken egg inner shell membranes and to capture useful dynamic characteristics associated with delicate tissue manipulations.

Micro-force sensing in robot assisted membrane peeling for vitreoretinal surgery

Vitreoretinal surgeons use 0.5 mm diameter instruments to manipulate delicate tissue inside the eye while applying imperceptible forces that can cause damage to the retina. We present a system which robotically regulates user-applied forces to the tissue, to minimize the risk of retinal hemorrhage or tear during membrane peeling, a common task in vitreoretinal surgery. Our research platform is based on a cooperatively controlled microsurgery robot. It integrates a custom micro-force sensing surgical pick, which provides conventional surgical function and real time force information. We report the development of a new phantom, which is used to assess robot control, force feedback methods, and our newly implemented auditory sensory substitution to specifically assist membrane peeling. Our findings show that auditory sensory substitution decreased peeling forces in all tests, and that robotic force scaling with audio feedback is the most promising aid in reducing peeling forces and task completion time.

Single Fiber Optical Coherence Tomography Microsurgical Instruments for Computer and Robot-Assisted Retinal Surgery

We present initial prototype and preliminary experimental demonstration of a new class of microsurgical instruments that incorporate common path optical coherence tomography (CP-OCT) capabilities. These instruments may be used freehand or with robotic assistance. We describe a prototype 25 gauge microsurgical pick incorporating a single 125 microm diameter optical fiber interfaced to a Fourier Domain CP-OCT system developed in our laboratory. For initial experimentation, we have interfaced this instrument with an extremely precise, cooperatively controlled robot. We describe the tool, system design, and demonstration of three control methods on simple phantom models: 1) enforcement of safety constraints preventing unintentional collisions of the instrument with the retinal surface; 2) the ability to scan the probe across a surface while maintaining a constant distance offset; and 3) the ability to place the pick over a subsurface target identified in a scan and then penetrate the surface to hit the target.

Cooperative Robot Assistant for Retinal Microsurgery

This paper describes the development and results of initial testing of a cooperative robot assistant for retinal microsurgery. In the cooperative control paradigm, the surgeon and the robot share control of a tool attached to the robot through a force sensor. The system senses forces exerted by the operator on the tool and uses this information in various control modes to provide smooth, tremor-free, precise positional control and force scaling. The robot manipulator is specifically designed with retinal microsurgery in mind, having high efficacy, flexibility and ergonomics while meeting the accuracy and safety requirements of microsurgery. We have tested this robot on a biological model and we report the results for reliably cannulating approximately 80 microm diameter veins (equivalent in size to human retinal veins). We also describe improvements to the robot and the experimental setup facilitating more advanced set of experiments.

Force sensing micro-forceps with integrated fiber Bragg grating for vitreoretinal surgery

Vitreoretinal surgery is a technically demanding ophthalmologic discipline. One of the main technical challenges in vitreoretinal surgery is the lack of force sensing since the surgical maneuvers fall below the human sensory threshold. Previously, a 2-degree-of-freedom (DOF) force sensing instrument with a surgical pick was developed and tested. However, a more commonly used instrument for vitreoretinal surgery is the forceps, with which a surgeon can easily grasp and delaminate the scar tissue. We have designed, fabricated and calibrated a novel 20-gauge (Ga) microsurgical instrument with a 2-DOF force sensing forceps. Three fiber Bragg grating (FBG) sensors are integrated into the customized AlconTM forceps tip. The redundant sensor configuration provides good compensation for temperature-related drift. The calibration data show that the tool can provide a force resolution of 0.25 mN. In order to test the functionality and performance, the forceps was evaluated in inner shell membrane peeling experiments with chicken embryos as well as in in-vivo rabbit experiments. The instrument has demonstrated the capability of being applied in the clinical environment, with consistent force measurements. The force exerted in inner shell membrane peeling is from 6.07 to 34.65 mN. The development of the 2-DOF force sensing micro-forceps has shown that the fabrication process is feasible and reliable, and it can be used to develop a future 3-DOF force sensing tool.

Force sensing micro-forceps for robot assisted retinal surgery

Membrane peeling is a standard vitreoretinal procedure, where the surgeon delaminates a very thin membrane from retina surface using surgical picks and forceps. This requires extremely delicate manipulation of the retinal tissue. Applying excessive forces during the surgery can cause serious complications leading to vision loss. For successful membrane peeling, most of the applied forces need to be very small, well below the human tactile sensation threshold. In this paper, we present a robotic system that combines a force sensing forceps tool and a cooperatively-controlled surgical robot. This combination allows us to measure the forces directly at the tool tip and use this information for limiting the applied forces on the retina. This may prevent many iatrogenic injuries and allow safer maneuvers during vitreoretinal procedures. We show that our system can successfully eliminate hand-tremor and excessive forces in membrane peeling experiments on the inner shell membrane of a chicken embryo.

Visual tracking of surgical tools for proximity detection in retinal surgery

In retinal surgery, surgeons face difficulties such as indirect visualization of surgical targets, physiological tremor and lack of tactile feedback. Such difficulties increase the risks of incorrect surgical gestures which may cause retinal damage. In this context, robotic assistance has the potential to overcome current technical limitations and increase surgical safety. In this paper we present a method for robustly tracking surgical tools in retinal surgery for detecting proximity between surgical tools and the retinal surface. An image similarity function based on weighted mutual information is specially tailored for tracking under critical illumination variations, lens distortions, and rapid motion. The proposed method was tested on challenging conditions using a phantom eye and recorded human in vivo data acquired by an ophthalmic stereo microscope.

Towards automatic calibration of Fourier-Domain OCT for robot-assisted vitreoretinal surgery

We present a new real-time automatic spectral calibration (ASC) method for Fourier domain optical coherence tomography (FD OCT) that can be automatically performed by the system. The ASC method proposed can be performed during OCT scanning operation and does not require an external calibrating light source or a commercial optical spectrum analyzer. Spectral data used for calibration can be interferograms obtained from an arbitrary sample which may have complicated internal structures, such as ones found in biological tissue. Moreover, our ASC method incorporates known robot motion to calibrate physical pixel spacing of the A-scan in static or dynamic environments. Experimental results show that our ASC method can provide high-performance calibration for FD OCT in terms of axial resolution and ranging accuracy without increasing hardware complexity.

Development and preliminary data of novel integrated optical micro-force sensing tools for retinal microsurgery

This paper reports the development of novel micro-force sensing tools for retinal microsurgery. Retinal microsurgery requires extremely delicate manipulation of retinal tissue, and tool-to-tissue interaction forces are frequently below human perceptual thresholds. Further, the interaction between the tool shaft and sclera makes accurate sensing of forces exerted on the retina very difficult with previously developed force sensing schemes, in which the sensor is located outside the eye. In the work reported here, we incorporate 160 µm Fiber Bragg Grating (FBG) strain sensors into the tool shaft to sense forces distal to the sclera. The sensor is applicable both with robotically manipulated and freehand tools. Preliminary results with a 1 degree-of-freedom (DOF) sensor have demonstrated 0.25 mN resolution, and work is underway to develop 2 and 3 DOF tools. The design and analysis of the force sensing tool is presented with preliminary testing data and some initial experiments using the tool with both freehand and robotic manipulation.

Preliminary evaluation of a micro-force sensing handheld robot for vitreoretinal surgery

Highly accurate positioning is fundamental to the performance of vitreoretinal microsurgery. Of vitreoretinal procedures, membrane peeling is among the most prone to complications since extremely delicate manipulation of retinal tissue is required. Associated tool-to-tissue interaction forces are usually below the threshold of human perception, and the surgical tools are moved very slowly, within the 0.1-0.5 mm/s range. During the procedure, unintentional tool motion and excessive forces can easily give rise to vision loss or irreversible damage to the retina. A successful surgery includes two key features: controlled tremor-free tool motion and control of applied force. In this study, we present the potential benefits of a micro-force sensing robot in vitreoretinal surgery. Our main contribution is implementing fiber Bragg grating based force sensing in an active tremor canceling handheld micromanipulator, known as Micron, to measure tool-to-tissue interaction forces in real time. Implemented auditory sensory substitution assists in reducing and limiting forces. In order to test the functionality and performance, the force sensing Micron was evaluated in peeling experiments with adhesive bandages and with the inner shell membrane from chicken eggs. Our findings show that the combination of active tremor canceling together with auditory sensory substitution is the most promising aid that keeps peeling forces below 7 mN with a significant reduction in 2-20 Hz oscillations.