Remote Center Of Motion Research Articles

Kinematic design considerations for minimally invasive surgical robots: an overview

Kinematic design is a predominant phase in the design of robotic manipulators for minimally invasive surgery (MIS). However, an extensive overview of the kinematic design issues for MIS robots is not yet available to both mechanisms and robotics communities. Hundreds of archival reports and articles on robotic systems for MIS are reviewed and studied. In particular, the kinematic design considerations and mechanism development described in the literature for existing robots are focused on. The general kinematic design goals, design requirements, and design preferences for MIS robots are defined. An MIS-specialized mechanism, namely the remote center-of-motion (RCM) mechanism, is revisited and studied. Accordingly, based on the RCM mechanism types, a classification for MIS robots is provided. A comparison between eight different RCM types is given. Finally, several open challenges for the kinematic design of MIS robotic manipulators are discussed. This work provides a detailed survey of the kinematic design of MIS robots, addresses the research opportunity in MIS robots for kinematicians, and clarifies the kinematic point of view to MIS robots as a reference for the medical community.

Development of a medical robot system for minimally invasive surgery

Robot-assisted systems have been widely used in minimally invasive surgery (MIS) practice, and with them the precision and accuracy of surgical procedures can be significantly improved. Promoting the development of robot technology in MIS will improve robot performance and help in tackling problems from complex surgical procedures. A medical robot system with a new mechanism for MIS was proposed to achieve a two-dimensional (2D) remote centre of motion (RCM). An improved surgical instrument was designed to enhance manipulability and eliminate the coupling motion between the wrist and the grippers. The control subsystem adopted a master-slave control mode, upon which a new method with error compensation of repetitive feedback can be based for the inverse kinematics solution. A unique solution with less computation and higher satisfactory accuracy was also obtained. Tremor filtration and trajectory planning were also addressed with regard to the smoothness of the surgical instrument movement. The robot system was tested on pigs weighing 30-45 kg. The experimental results show that the robot can successfully complete a cholecystectomy and meet the demands of MIS. The results of the animal experiments were excellent, indicating a promising clinical application of the robot with high manipulability.

An External Positioning Mechanism for Robotic Surgery

Current surgical robotic systems have shown that the robotic approach bring many benefits to both surgeons and patients. However, these systems still need further improvements to increase dexterity and to facilitate a cost-effective integration in any standard operating room. With this goal, we propose a compact and accurate positioning mechanism, called Dionis. This spatial hybrid mechanism based on a parallel kinematics provides three rotations and one translation for single incision laparoscopy. The corresponding axes intersect at a remote center of motion that is coincident with the entry point into the patient's abdominal cavity. In addition, the compact design of the Dionis robot allows direct access to the patient, without removing the robotic system. This, besides saving precious space in the operating room, improves safety over existing solutions. This article presents the conceptual design of the Dionis robot followed by its workspace and dynamic analysis. The required maximum speed and maximum torque of the actuators are obtained for a set of typical trajectories to chose the most appropriate actuators. The final design and a summary of the control architecture are as well described.

Assessment of a Hexapod Surgical System for Robotic Micro-Macro Manipulations in Ocular Surgery

Purpose: Robotic intraocular microsurgery requires a remote center of motion (RCM) at the site of ocular penetration. We designed and tested the Hexapod Surgical System (HSS), a microrobot mounted on the da Vinci macrorobot for intraocular microsurgery. Material and Methods: Translations and rotations of the HSS were tested for range of motion and stability. Precision and dexterity were assessed by pointing and inserting a coupled probe into holes of various sizes. The stability of a nonmechanical RCM was quantified. HSS functionalities were observed on porcine eyes. Results: The HSS maximal translations were 10 (x and y axes) and 5 cm (z axis). The maximal rotations were 15 and 22° (x and y axes). The precision was within 0.5 mm away from targets in 26/30 tests and maximal in 16/30 tests. The mean translational and rotational stability at the tip of the probe were 1.2 (0.6–1.9) and 1 mm (0–2), respectively. The average dexterity times were 5.2 (4.4–6.5), 7.1 (5.6–10.8) and 12.3 s (7.8–21.7) for 5-, 2- and 1-mm holes, respectively. The RCM was stable (within 0.1 mm). A vitreous cutter coupled to the HSS moved into porcine eyes through a sclerotomy with a stable RCM. Conclusion: The HSS provides an RCM dedicated for intraocular robotic surgery with a high level of precision and dexterity. Although it can be further improved, the micro-macro robotic system is a feasible approach for ocular surgery.

Three‐dimensional ultrasound image‐guided robotic system for accurate microwave coagulation of malignant liver tumours

The further application of conventional ultrasound (US) image-guided microwave (MW) ablation of liver cancer is often limited by two-dimensional (2D) imaging, inaccurate needle placement and the resulting skill requirement. The three-dimensional (3D) image-guided robotic-assisted system provides an appealing alternative option, enabling the physician to perform consistent, accurate therapy with improved treatment effectiveness. Our robotic system is constructed by integrating an imaging module, a needle-driven robot, a MW thermal field simulation module, and surgical navigation software in a practical and user-friendly manner. The robot executes precise needle placement based on the 3D model reconstructed from freehand-tracked 2D B-scans. A qualitative slice guidance method for fine registration is introduced to reduce the placement error caused by target motion. By incorporating the 3D MW specific absorption rate (SAR) model into the heat transfer equation, the MW thermal field simulation module determines the MW power level and the coagulation time for improved ablation therapy. Two types of wrists are developed for the robot: a 'remote centre of motion' (RCM) wrist and a non-RCM wrist, which is preferred in real applications. The needle placement accuracies were < 3 mm for both wrists in the mechanical phantom experiment. The target accuracy for the robot with the RCM wrist was improved to 1.6 +/- 1.0 mm when real-time 2D US feedback was used in the artificial-tissue phantom experiment. By using the slice guidance method, the robot with the non-RCM wrist achieved accuracy of 1.8 +/- 0.9 mm in the ex vivo experiment; even target motion was introduced. In the thermal field experiment, a 5.6% relative mean error was observed between the experimental coagulated neurosis volume and the simulation result. The proposed robotic system holds promise to enhance the clinical performance of percutaneous MW ablation of malignant liver tumours.

Preliminary clinical experiences of a motorized manipulator for magnetic resonance image–guided microwave coagulation therapy of liver tumors

Background In magnetic resonance (MR) image–guided microwave thermocoagulation of liver tumors, the choice of the optimal puncture route is an important and time-consuming process. To assist this process, we have developed a motorized MR-compatible manipulator. Methods The manipulator consists of a passive end effecter with 2 degrees-of-freedom (DOF) rotation and active base stages with 3 ultrasonic motors. It automatically chases the preset target point with synergetic remote-center-of-motion (RCM) control. A mechanical torque limiter and an electrical shutdown switch were added for patient safety. Results The manipulator was used for this procedure in 15 cases and successfully utilized to treat liver tumors in various locations. Thoracoscopic assistance was combined with the manipulator in 6 cases. No complications were experienced. Conclusions The manipulator was found to be very effective for assisting MR-guided microwave coagulation of liver tumors.

Modélisation, commande géométrique et utilisation d'un robot portable de télé-échographie : Teresa

This paper presents a 4 DOF, non-redundant tele-operated robotic system, compact and portable with a remote centre of motion. This body mounted system provides medical experts the ability to remotely carry out, in real time, an ultrasound examination on a distant patient. The robot can rotate a standard ultrasound probe in almost any orientation, with a maximum inclination of 45° with respect to the ascendant normal of the patient's skin. A trade off was made between on the one hand, the compactness, ergonomy and security, and on the other hand the kinematics performance of the robot. This compromise led to a solution including two singularity branches. As we could access a closed-form kinematics model of the robot with well-conditioned equations, efficient control laws were implemented and also were able to manage these singularities. The concept of robotised tele-echography was clinically validated by, in more than 80 % of the cases, a good pre-diagnosis comparable to the one obtained in classical examinations.

Type Synthesis for One-dimensional Remote-center-of-motion Mechanisms

The type synthesis for one-dimensional remote center of motion(RCM) mechanisms is the base of the study of multi-DOF RCM mechanism.Due to types of present RCM mechanisms are few,it is necessary to find an efficient way to create more new RCM mechanisms.Existing 1-DOF RCM mechanisms are classified.Five types of RCM mechanisms are given,such as single-revolute-joint,circular-prismatic-joint,parallelogram-based,synchronous-transmission-based and instantaneous RCM mechanisms.Based on a proposed concept of the planar virtual center(VC) mechanism,which is a more generalized concept than an RCM mechanism,an approach of type synthesis for 1-DOF RCM mechanisms is addressed by assembling two planar VC mechanisms.This approach can synthesize parallel or mixed RCM mechanisms.Concrete examples are given,and some new configurations are obtained,and which proves the effectiveness of the type synthesis method.

MRI‐compatible manipulator with remote‐center‐of‐motion control

To develop and assess a needle-guiding manipulator for MRI-guided therapy that allows a physician to freely select the needle insertion path while maintaining remote center of motion (RCM) at the tumor site. The manipulator consists of a three-degrees-of-freedom (DOF) base stage and passive needle holder with unconstrained two-DOF rotation. The synergistic control keeps the Virtual RCM at the preplanned target using encoder outputs from the needle holder as input to motorize the base stage. The manipulator assists in searching for an optimal needle insertion path which is a complex and time-consuming task in MRI-guided ablation therapy for liver tumors. The assessment study showed that accuracy of keeping the virtual RCM to predefined position is 3.0 mm. In a phantom test, the physicians found the needle insertion path faster with than without the manipulator (number of physicians = 3, P = 0.001). However, the alignment time with the virtual RCM was not shorter when imaging time for planning were considered. The study indicated that the robot holds promise as a tool for accurately and interactively selecting the optimal needle insertion path in liver ablation therapy guided by open-configuration MRI.

Classification and type synthesis of 1-DOF remote center of motion mechanisms

Abstract Type synthesis of 1-DOF remote center of motion (RCM) mechanisms is the preliminary for research on many multi-DOF RCM mechanisms. Since types of existing RCM mechanisms are few, it is necessary to find an efficient way to create more new RCM mechanisms. In this paper, existing 1-DOF RCM mechanisms are first classified, then base on a proposed concept of the planar virtual center (VC) mechanism, which is a more generalized concept than a RCM mechanism, two approaches of type synthesis for 1-DOF RCM mechanisms are addressed. One case is that a 1-DOF parallel or serial–parallel RCM mechanism can be constructed by assembling two planar VC mechanisms; the other case, a VC mechanism can be expanded to a serial–parallel RCM mechanism. Concrete samples are provided accordingly, some of which are new types.

Optimizing port placement for robot‐assisted minimally invasive cardiac surgery

Proper placement of ports during robot-assisted endoscopic surgery is critical to the success of the procedure. In current practice, port placement methods do not consider the ability of the robot to manoeuvre the tools. This paper proposes to choose the best port location such that the performance of the robot is maximized. The Global Conditioning Index (GCI) is used to optimize port placement when using the da Vinci((R)) surgical system during cardiac surgery. The results show that, due to a singularity at the remote centre of motion, higher performance is obtained the further away the port is from the workspace. When compared to the ports selected by an expert surgeon, our results show that it is possible to increase robot performance by at least 29% for the left arm of the robot. Selecting an adequate port location can improve robot performance and ensure that the instruments reach the surgical site.

Design, calibration and evaluation of a robotic needle-positioning system for small animal imaging applications

A needle-positioning robot has been developed for image-guided interventions in small animal research models. The device is designed to position a needle with an error ⩽100 µm. The robot has two rotational axes (pitch and roll) to control needle orientation, and one linear axis to perform needle insertion. The three axes intersect at a single point to create a remote centre of motion (RCM) that acts as a fulcrum for the orientation of the needle. The RCM corresponds to the skin-entry point of the needle into the animal. The robot was calibrated to ensure that the three axes intersected at a single point defining an RCM and that the needle tip was positioned at the RCM. Needle-positioning accuracy and precision were quantified in Cartesian coordinates at ten target locations in the plane of each rotational axis. The measured needle-positioning accuracy in free space was 54 ± 12 µm for the pitch axis plane and 91 ± 21 µm for the roll axis plane. The measured needle-positioning precision was 15 and 17 µm for the pitch and roll axes planes, respectively. The robot's ability to insert a needle into a tumour in a euthanized mouse was demonstrated.

Design of double parallelogram remote-center-of-motion mechanisms

The double parallelogram type of remote center of motion (RCM) mechanisms is generally used as wrist module in minimally invasive surgery (MIS) assisted robots, which can provide a fixed entry point during operation process, enhance safety and quality of the surgery, and give facilities for surgeons. With type synthesis, 10 types of double parallelogram RCM mechanisms are enumerated. By making some links crooked, the virtual center can be arranged properly, which also makes the arrangements of end-effector and motor more convenient. In order to design a double parallelogram RCM mechanism, six independent parameters are needed. The forces and structure stiffness of linkage are analyzed to assist in determining sectional sizes of links. The driven moment is estimated to select a right motor. The analysis shows that a double parallelogram RCM mechanism can be balanced by one counterweight. At last, an example is given to illuminate the mechanism's feasibility and validity.

Sci‐PM Fri ‐ 04: A three‐dimensional micro‐ultrasound image‐guided and robotically assisted needle positioning system

Biomedical research using small animals often requires interventional procedures such as biopsies and injections. When performed inaccurately, these procedures can produce poor results, jeopardizing the study. A needle‐positioning robot for three‐dimensional micro‐ultrasound guided interventions was developed to improve the accuracy of needle insertion. The robot has three degrees of freedom for positioning the needle in three dimensions. Two rotational joints are used to control orientation (roll and pitch), while another joint linearly translates the needle to perform insertion. The three axes intersect at a single point, producing a remote centre of motion (RCM) that acts as a fulcrum for the three‐dimensional orientation of the needle. The RCM corresponds to the insertion point of the needle into the animal. The robot was calibrated to ensure that the three axes intersected at a single point, and that the needle tip was positioned at the RCM. The calibration was performed using a high‐resolution digital camera to find the centre of rotation about the pitch and roll axes separately. The position of the needle was adjusted until it was aligned with the RCM. Calibration results indicate that the distance from the needle to the pitch and roll axes are 24±30 μm and 18±15 μm, respectively. The pitch and roll axes are separated by 11±3 μm. The calibration procedure allowed us to detect and correct manufacturing and design errors. The expected maximum needle positioning error computed from the calibration is 32 μm when the needle tip is moved to the boundary of the workspace.

WE‐D‐I‐609‐01: Design and Calibration of a Robotic Needle Positioning System for Small Animal Imaging Applications

Purpose: A needle‐positioning robot is being developed for three‐dimensional micro‐ultrasound guided interventions. This device will be used to perform minimally invasive injections and biopsies into small animals with high accuracy and precision. Method and Materials: The robot has three degrees of freedom for positioning the needle in three dimensions. Two rotational joints are used to control needle orientation (roll and pitch). Another joint linearly translates the needle to perform insertion. The design features a four‐bar linkage mechanism that translates the roll axis of rotation from an actuator to a remote axis that intersects the pitch and needle axes. The three intersecting axes create a remote center of motion (RCM) that acts as a fulcrum for the three‐dimensional orientation of the needle. The RCM corresponds to the insertion point of the needle into the animal. In order for the robot to achieve high accuracy, it must be calibrated to ensure that the three axes intersect at a single point, and the needle tip must be positioned at the RCM. The calibration was performed using a macro lens CCD camera to find the center of rotation about the pitch and roll axes separately. The position of the needle was adjusted until it was aligned with the RCM. Results: The range of motion is ±30°, ±45°, and 20 mm for the pitch, roll, and needle axes, respectively. Initial calibration results indicate that the distance from the needle to the pitch and roll axes are 24 ± 30 μm (mean ± standard deviation of five trials) and 18 ± 15 μm, respectively. The pitch and roll axes are separated by 11 ± 3 μm. Conclusion: The expected maximum needle positioning error computed from the calibration results is 32 μm when the needle tip is moved to the boundary of the workspace.

A tele-operated mobile ultrasound scanner using a light-weight robot

This paper presents a new tele-operated robotic chain for real-time ultrasound image acquisition and medical diagnosis. This system has been developed in the frame of the Mobile Tele-Echography Using an Ultralight Robot European Project. A light-weight six degrees-of-freedom serial robot, with a remote center of motion, has been specially designed for this application. It holds and moves a real probe on a distant patient according to the expert gesture and permits an image acquisition using a standard ultrasound device. The combination of mechanical structure choice for the robot and dedicated control law, particularly nearby the singular configuration allows a good path following and a robotized gesture accuracy. The choice of compression techniques for image transmission enables a compromise between flow and quality. These combined approaches, for robotics and image processing, enable the medical specialist to better control the remote ultrasound probe holder system and to receive stable and good quality ultrasound images to make a diagnosis via any type of communication link from terrestrial to satellite. Clinical tests have been performed since April 2003. They used both satellite or Integrated Services Digital Network lines with a theoretical bandwidth of 384 Kb/s. They showed the tele-echography system helped to identify 66% of lesions and 83% of symptomatic pathologies.

Virtual Remote Center of Motion control for needle placement robots

Objective: We present an algorithm that enables percutaneous needle-placement procedures to be performed with unencoded, unregistered, minimally calibrated robots while removing the constraint of placing the needle tip on a mechanically enforced Remote Center of Motion (RCM).Materials and Methods: The algorithm requires only online tracking of the surgical tool and a five-degree-of-freedom (5-DOF) robot comprising three prismatic DOF and two rotational DOF. An incremental adaptive motion control cycle guides the needle to the insertion point and also orients it to align with the target-entry-point line. The robot executes RCM motion without having a physically constrained fulcrum point.Results: The proof-of-concept prototype system achieved 0.78 mm translation accuracy and 1.4° rotational accuracy (this is within the tracker accuracy) within 17 iterative steps (0.5–1 s).Conclusion: This research enables robotic assistant systems for image-guided percutaneous procedures to be prototyped/constructed more quickly and less expensively than has been previously possible. Since the clinical utility of such systems is clear and has been demonstrated in the literature, our work may help promote widespread clinical adoption of this technology by lowering system cost and complexity.

A remote center of motion robotic arm for computer assisted surgery

SummaryWe have designed a robotic arm based on a double parallel four bar linkage to act as an assistant in minimally invasive surgical procedures. The remote center of motion (RCM) geometry of the robot arm kinematically constraints the robot motion such that minimal translation of an instrument held by the robot takes place at the entry portal into the patientApos;s body. In addition to the two rotational degrees of freedom comprising the RCM arm, distal translation and rotation are provided to manoeuver the instrument within the patient's body about an axis coincident with the RCM. An XYZ translation stage located proximal to the RCM arm provides positioning capability to establish the RCM location relative to the patients anatomy. An electronics set capable of controlling the system, as well as performing a series of safety checks to verify correct system operation, has also been designed and constructed. The robot is capable of precise positional motion. Repeatability in the ±10 micron range is demonstrated. The complete robotic system consists of the robot hardware and an IBM PC-AT based servo controller connected via a custom shared memory link to a host IBM PS/2. For laparoscopic applications, the PS/2 includes an image capture board to capture and process video camera images. A camera rotation stage has also been designed for this application. We have successfully demonstrated this system as an assistant in a laparoscopic cholecystectomy. Further applications for this system involving active tissue manipulation are under development.