During robot-assisted surgery, a Remote Center of Motion (RCM) is often implemented to constrain instrument motion through and about a specific point in space. Aligning and re-positioning this point during surgery is not trivial, as this is a defined, yet often non-visualised, point in space. When misaligned with the patient surrounding anatomy is excessively strained, potentially causing post-operative complications. Not being able to safely re-position the RCM for these purposes limits the use of surgical robotics. This work introduces a general approach relying on anatomy-based haptic fixtures to simplify and improve RCM positioning during robot-assisted surgery. The proposed approach is extended with a novel method and mechanism to mechanically implement such fixtures. This is applied for the use case of vitreoretinal surgery, for which purpose a dedicated robotic setup and fixture mechanism was developed. These were used to conduct an initial experimental validation, during which the feasibility of both a virtual and mechanical implementation is reviewed. Initial outcomes suggest that both implementations are feasible. With the currently used impedance-type system, the mechanical implementation is shown to offer at least one order of magnitude stiffness increase when compared to an equivalent virtual implementation.

At the moment, surgeons struggle curing a widespread eye disease known as retinal vein occlusion where clots obstruct the retinal vessels. Latter vascular disorder involves black spots in people's eyesight and lead eventually to blindness. A recent promising treatment consists in flushing a thrombolytic agent inside the clotted retinal vessels. The surgery implies puncturing vessels ranging from 50 to 400 microns diameter on the backside of the eye, namely the retina. Latest research succeeded in tackling several challenges around this operation: the surgeon's hand tremor and the high precision required amongst other requirements. Despite several breakthroughs, the surgeon only relies on a microscope to perform the surgery through the patient eye's lens, giving poor depth perception to properly puncture the retinal vessels. This way, the surgeon is most likely to pierce through the vessel and inject the thrombolytic drug under the retina, which would endanger the person's eyesight. In this paper, we investigate the use of a novel bio-impedance sensor developed for eye surgery. Together with this new sensor, a detection algorithm has been developed to detect the puncture and double puncture events to give a feedback to the operator of the system. As far as we are aware of, such technology doesn't exist yet in eye surgery to tackle the depth perception question. This paper aims at demonstrating the benefits of this technology.

Retinal Vein Occlusion is a common retinal vascular disorder which can cause severe loss of vision. Retinal vein cannulation followed by injection of an anti-coagulant into the affected vein is a promising treatment. However, given the scale and fragility of the surgical workfield, this procedure is considered too high-risk to perform manually. A first successful robot-assisted procedure has been demonstrated. Even though successful, the procedure remains extremely challenging. This paper aims at providing a solution for the limited perception of instrument-tissue interaction forces as well as depth estimation during retinal vein cannulation. The development of a novel combined force and distance sensing cannulation needle relying on Fiber Bragg grating (FBG) and Optical Coherence Tomography (OCT) A-scan technology is reported. The design, the manufacturing process, the calibration method, and the experimental characterization of the produced sensor are discussed. The functionality of the combined sensing modalities and the real-time distance estimation algorithm are validated respectively on in-vitro and ex-vivo models.

Surgical interventions are increasingly executed minimal invasively. Surgeons insert instruments through tiny incisions in the body and pivot slender instruments to treat organs or tissue below the surface. While a blessing for patients, surgeons need to pay extra attention to overcome the fulcrum effect, reduced haptic feedback and deal with lost hand-eye coordination. The mental load makes it difficult to pay sufficient attention to the forces that are exerted on the body wall. In delicate procedures such as fetal surgery, this might be problematic as irreparable damage could cause premature delivery. As a first attempt to quantify the interaction forces applied on the patient's body wall, a novel 6 degrees of freedom force sensor was developed for an ex-vivo set up. The performance of the sensor was characterised. User experiments were conducted by 3 clinicians on a set up simulating a fetal surgical intervention. During these simulated interventions, the interaction forces were recorded and analysed when a normal instrument was employed. These results were compared with a session where a flexible instrument under haptic guidance was used. The conducted experiments resulted in interesting insights in the interaction forces and stresses that develop during such difficult surgical intervention. The results also implicated that haptic guidance schemes and the use of flexible instruments rather than rigid ones could have a significant impact on the stresses that occur at the body wall.

Accurate and precise control of catheters inside a vasculature is a difficult yet important task. Current manual approaches require significant surgical skill. Over the years, surgeons build up a sort of mental kinematic map telling them how to handle the catheter in order to steer the catheter tip safely through the vessel system. The input-output behaviour of the catheter is complex and depends heavily on its configuration within and contacts with the vasculature. This paper introduces an alternative approach to control robotic catheters. The input-output behaviour or so-called differential kinematics are derived from a patient-specific vasculature model, following a minimum-energy argumentation. The validity of the proposed approach is demonstrated experimentally. Whereas the performance of model-based approaches is obviously greatly influenced by the correctness of estimated parameters, within this work we show experimentally how reasonable performance can already be achieved within the setup that was constructed. We expect that there is still ample room for improvement by, e.g., putting more sophisticated identification, modeling and collision detection schemes into place.

Lasers are being used in various surgical procedures to remove tissue or bones, to coagulate vessels or other structures. Due to difficulties in handling only a limited number of surgeons manage to display sufficient levels of precision in Minimally Invasive Surgery (MIS) procedures. Prior works on robotic laser surgery demonstrated shorter learning curves and higher ablation precision, but unfortunately ignored the fact that most clinically relevant tasks are bi-manual by nature. Surgeons are also reluctant to use current commercial surgical robotic systems for complex laser tasks, indicating that the lack of haptic feedback prevents them from efficient and safe tissue handling in preparation of laser treatment. This paper expands earlier robotic laser work towards bi-manual operation. The paper introduces a system for precisely tensioning tissue that is being targeted by the laser. An artificial test-setup that captures some essential features of bimanual laser surgery is described. Experiments have been conducted to investigate the effect of haptic feedback on ablation performance. A comparison is made of achievable levels of ablation precision when there is no haptic feedback, when there is haptic feedback and when an automatic tension control algorithm is deployed. The conducted experimental results confirm the great potential of haptic feedback and automatic tensioning systems for complex bi-manual lasering tasks.

Retinal Vein Occlusion is a common retinal vascular disorder which can cause severe loss of vision. Retinal vein cannulation and subsequent injection of anti-coagulant in the affected vein is a promising treatment. Given the scale and the fragility of retinal veins on one side and the surgeons limited positioning precision and force perception on the other side, this procedure is considered too risky to perform manually at the moment. The paper tackles the limited force perception problem. The development of a novel force sensing cannulation needle based on Fiber Bragg Gratings is reported. The design, the calibration method and the experimental characterization of the produced force sensor are discussed. The functionality of the needle is validated by measuring puncture forces during cannulations in a custom-made retina model.

A novel fluidic actuation system has been developed for in situ imaging of anatomic tissues. The actuator consists of a micromachined superelastic tool guide driven by a pair of pneumatic artificial muscles. Two additional working channels allow easy interchange of instruments or sensing equipment. This paper describes the design and construction of the actuation system. Experimental results are also reported indicating a bending repeatability of 0.1 degrees and an operational bandwidth exceeding 8Hz. To show-case the performance of the device, the actuator was loaded with an all-optical ultrasound imaging probe. First scanned images of human placental tissue surface using an all-optical ultrasound probe are presented. While a model has been developed to estimate the probe position in space as function of the input pressure, in future work, this model will be complemented with additional sensor measurements of the bending probe taking into account the hysteretic behaviour of both muscles and nitinol structure.

Advances in miniature surgical instrumentation are key to less invasive and safer medical interventions. In cardiovascular procedures interventionalists turn towards catheter-based interventions, treating patients considered unfit for classical more invasive approaches. Improvements in design and steerability of catheters could further reduce the invasiveness of these interventions. For example, by improving controllability and interaction forces with the vessels, tissue damage could be limited. Through improved steerability and coordinated control, operation times and exposure to radiation might also be reduced. Latter argument formed the original motivation for the development of teleoperated robotic catheters. Despite the large kinematic dissimilarity and thus non-trivial mapping between joystick input and catheter output motion, few investigations have been conducted to find intuitive mappings that allow straightforward catheter steering. This paper presents some recent work in this direction. Three promising mappings are proposed. The mappings were implemented and validated upon a robotic catheter moving inside an artificial aorta model. Experimental results show good steerability of the robotic catheter for all the mappings. Although superiority of one mapping with respect to the others was observed, further investigation and validation is planned. In the future, additional visual cues that increase the situational awareness of the user are expected to further simplify the steering.

This paper introduces a framework for constraint-based force/position control of robots that exhibit large nonlinear structural compliance and that undergo large deformations. Controller synthesis follows hereto the principles of the Task Frame and instantaneous Task Specification using Constraints (iTaSC) formalisms. iTaSC is found particularly suitable due to its ability to express and combine control tasks in a natural way. Control tasks can be formulated as combinations of target positions, velocities, or forces expressed in an arbitrary number and type of coordinate frames. The proposed framework is applied to a mixed mechatronic system composed of a traditional rigid-link robot whose end-effector is a continuum (flexible) link. A selection of different position/force control tasks is prepared to demonstrate the validity and general nature of the proposed framework.

Retinal surgery is one of the most challenging types of surgery because of the scale and the fragility of the human eye anatomy. The surgeon suffers from limited positioning accuracy, tremor and poor force feedback directly affecting the quality of the surgical procedures. To tackle these issues, we developed a teleoperation system to assist surgeons during retinal surgery. The system offers features like motion scaling, tremor compensation and scaled force feedback. This paper reports on the design of the slave and the master.

This paper presents a mathematical formulation for calculation of the compliance of continuum type of robots. The mathematical model of the continuum robot is built following the Cosserat rod theory and focuses on a single section Cosserat rod under arbitrary loading. The compliance of the robot is described as a set of ordinary differential equations with split boundary conditions. This new set of compliance equations is directly coupled to the solution of the forward kinematics of the robot. After solving the forward kinematics problem, these solutions can be directly used to compute the compliance. A particular class of continuum robots in which the compliance of the robot can be formulated as an initial value problem and solved in a single numerical integration is discussed. The paper provides experimental validation of the proposed method.

This paper describes a force-measuring manipulator for minimally invasive surgery. It employs an extracorporeal force measurement system combined with a passive trocar support to deal with the restrictions of a single insertion point in the body. The first contribution is the detailed description of the design and the involved kinematics of the device and the force measurement system, while the second contribution is an extensive performance evaluation including an in vivo animal experiment. During the latter, endoscopic video images were recorded simultaneously with motion and force information of the instrument tip. Breathing effects, contact with other instruments and nonlinear soft tissue stiffness could be detected by the system, indicating its potential as a MIS manipulator and as an in vivo tissue property measurement tool.

Retinal Vein Occlusion (RVO) is a common retinal vascular disorder which may cause severe loss of vision. Retinal cannulation appears to be the most effective treatment, but given the small diameter of a retinal vein, it is too difficult and risky for a surgeon to perform this procedure manually. This work reports on the development of an innovative robotic manipulator to assist vitreoretinal surgeons during this procedure using a co-manipulation control strategy. The robotic manipulator features a new Remote-Center-of-Motion mechanism with four degrees of freedom. This mechanism is particularly interesting for applications in minimally invasive surgery where an instrument needs to be manoeuvred in a highly confined space around a fixed incision point. The developed manipulator is shown to be a great asset in improving the quality of retinal cannulations compared to the manual procedure. This is shown by cannulation experiments performed on a custom made eye model and an injectable retina model that effectively simulate real retinal cannulations.

In this paper, the Bounded Environment Passivity method is applied to a 3-channel controller. This method enables the design of teleoperation controllers that show passive behaviour for interactions with a bounded range of environments.The resulting tuning guidelines, derived analytically, provide interesting tuning flexibility, which allows to focus on different aspects of transparency. As telesurgery is the motivation behind this work, the focus lies on correctly reflecting the stiffness properties of the environment. A comparison between the transparency and stability properties of this 3-channel controller and the same properties of the Position-Force controller demonstrates the interesting properties o fthe 3-channel controller. The theoretical results are verified experimentally on a 1 d.o.f. master-slave setup.

This paper derives analytic guidelines to tune the popular Position-Force bilateral controller and improve its performance by incorporating available knowledge on the bounds of the environment impedance. The proposed guidelines can prove especially useful in the domain of telesurgery where a need exists for well-understood bilateral teleoperation controllers, that show good performance and where many tasks can be characterized by restricted and relatively easily definable impedance regions. This paper firstly analyses the two-port passivity and absolute stability properties of two alternatives of the Position-Force controller. The limitations on achievable performance when guaranteeing absolute stability with arbitrary environments are detailed. Next, a novel method, called Bounded Environment Passivity method is introduced. This method enables the design of teleoperation controllers that show passive behaviour for interactions with an environment that varies over a given range of impedances. A set of guidelines that allow a smarter trade-off between performance and stability follows. The theoretical results are verified experimentally on a 1-d.o.f. teleoperation setup.

This paper describes an advanced tool guiding system for robot assisted surgery. It is offering two additional local degrees of freedom to a standard robotic tool guiding system like of the Zeus robotic surgery system. The tool guide is basically a tube that guides the inserted surgical instrument to the desired location. By adding two bending degrees of freedom at the tip, the developed system largely increases the maneuverability of the instrument. It consists of a micromachined superelastic tube driven by a conventional cable system. Main issue was the design of a flexible hinge system in superelastic NiTi that offers the desired bending angles (at least 90 degrees in both directions) and that is compatible with the material limits for long-time cycling. Based on extended FE calculations and experimental measurements the second-generation design offers 90 degrees bending in both directions. The improvement over previous devices is the combination of two degrees of freedom with a small diameter of only 5 mm. An additional advantage is the tool channel, which enables the use of different instruments with this single device.

The aim of this research is to apply a laparoscopic robot to improve and facilitate the procedures of laser laparoscopy performed by gynecological surgeons. We took advantages of the existing laparoscopic robot and made digitizer tablet and wireless pen as intuitive interface for this particular purpose. The What-You-Draw-is-What-You-Cut (WYDIWYC) control scheme provide surgeons a natural interface to perform laser ablation as he is sketching by pen. The auto-focus functionality helps surgeons to focus the laser automatically by an laparoscopic distance sensor. Some safety measures are installed in DSP controller. The accuracy of the robot is examined by a sinusoidal test and is more than the demand in laser laparoscopy. The simplicity of usage of the intuitive writing interface is demonstrated by a volunteer and shows the excellent results by cutting on an apple. Some considerations for safety issues are discussed in this paper.

This paper analyses scale effects for actuator types which are strong candidates for micro-actuation: shape memory alloys (SMAs), electrostatic, electromagnetic and piezoelectric actuators. SMA actuators are studied in detail and compared to the other actuator types on a basis of force, response time, and power density. Much of the analysis is based on thermal aspects and scaling effects on both convective and conductive heat transfer, which is a quite novel approach. Results of this thermal analysis are effects on surface temperature and maximum current density of microactuators.

Two new processes, ELID-grinding and high speed chipping, can combine high removal rates with high surface quality through a mechanism of sub-micron chip removal. For the successful application of these processes, ultra-precision positioning systems are needed. Classical solutions, based on traditional guideway technology, cannot meet the requirements of these new machining processes. The piezostepper solution presented in this paper can provide accurate motion, combined with high stiffness, through the use of piezoelectric actuators with high resolution. High passive stiffness is provided by integrating the driving, bearing and transmission functions. The same actuators can provide infinite active stiffness by referring the position of the positioning stage with respect to an absolute reference frame. In contrast with existing (position-controlled) piezo-steppers, this paper presents a way to provide smooth stepping by avoiding hammering through hybrid force-position controlled clamping and by rolling traction.