Guidance systems designed for neurosurgery, hip surgery, and spine surgery, and for approaches to other anatomy that is relatively rigid can use rigid-body transformations to accomplish image registration. These systems often rely on point-based registration to determine the transformation, and many such systems use attached fiducial markers to establish accurate fiducial points for the registration, the points being established by some fiducial localization process. Accuracy is important to these systems, as is knowledge of the level of that accuracy. An advantage of marker-based systems, particularly those in which the markers are bone-implanted, is that registration error depends only on the fiducial localization error (FLE) and is thus to a large extent independent of the particular object being registered. Thus, it should be possible to predict the clinical accuracy of marker-based systems on the basis of experimental measurements made with phantoms or previous patients. This paper presents two new expressions for estimating registration accuracy of such systems and points out a danger in using a traditional measure of registration accuracy. The new expressions represent fundamental theoretical results with regard to the relationship between localization error and registration error in rigid-body, point-based registration. Rigid-body, point-based registration is achieved by finding the rigid transformation that minimizes "fiducial registration error" (FRE), which is the root mean square distance between homologous fiducials after registration. Closed form solutions have been known since 1966. The expected value (FRE/sup 2/) depends on the number N of fiducials and expected squared value of FLE, (FLE/sup 2/), but in 1979 it was shown that (FRE/sup 2/) is approximately independent of the fiducial configuration C. The importance of this surprising result seems not yet to have been appreciated by the registration community: Poor registrations caused by poor fiducial configurations may appear to be good due to a small FRE value. A more critical and direct measure of registration error is the "target registration error" (TRE), which is the distance between homologous points other than the centroids of fiducials. Efforts to characterize its behavior have been made since 1989. Published numerical simulations have shown that (TRE/sup 2/) is roughly proportional to (FLE/sup 2/)/N and, unlike (FRE/sup 2/), does depend in some way on C. Thus, FRE, which is often used as feedback to the surgeon using a point-based guidance system, is in fact an unreliable indicator of registration-accuracy. In this work the authors derive approximate expressions for (TRE/sup 2/), and for the expected squared alignment error of an individual fiducial. They validate both approximations through numerical simulations. The former expression can be used to provide reliable feedback to the surgeon during surgery and to guide the placement of markers before surgery, or at least to warn the surgeon of potentially dangerous fiducial placements; the latter expression leads to a surprising conclusion: Expected registration accuracy (TRE) is worst near the fiducials that are most closely aligned! This revelation should be of particular concern to surgeons who may at present be relying on fiducial alignment as an indicator of the accuracy of their point-based guidance systems.

Predicting error in rigid-body point-based registration

This paper provides a broad overview of medical robot systems used in surgery. After introducing basic concepts of computer-integrated surgery, surgical CAD/CAM, and surgical assistants, it discusses some of the major design issues particular to medical robots. It then illustrates these issues and the broader themes introduced earlier with examples of current surgical CAD/CAM and surgical assistant systems. Finally, it provides a brief synopsis of current research challenges and closes with a few thoughts on the research/industry/clinician teamwork that is essential for progress in the field.

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Medical robotics in computer-integrated surgery

The invention is directed to manipulator assembly (2) for holding and manipulating a surgical instrument (14) in a telerobotic system. The manipulator assembly includes an instrument holder removably coupled to a drive assembly so that the holder can be sterilized. The assembly further includes a force sensing element (52) mounted distal to the holder and the drive assembly for detecting forces exerted on the surgical instrument and providing feedback to the surgeon. The invention is also directed to a system and method for releasably holding a surgical instrument (14). The system includes an instrument support for automatically locking mounting pins on the instrument within locking slots on the instrument holder to releasably couple the instrument to the holder. With a twist-lock motion, the surgeon can rapidly engage and disengage various instruments from the holder during a surgical procedure, such as open surgery, laparoscopy or thoracoscopy.

Surgical manipulator for a telerobotic system

The present method and apparatus use image processing to determine information about the position of a designated object. The invention is particularly useful in applications where the object is difficult to view or locate. In particular, the invention is used in endoscopic surgery to determine positional information about an anatomical feature within a patient's body. The positional information is then used to position or reposition an instrument (surgical instrument) in relation to the designated object (anatomical feature). The invention comprises an instrument which is placed in relation to the designated object and which is capable of sending information about the object to a computer. Image processing methods are used to generated images of the object and determine positional information about it. This information can be used as input to robotic devices or can be rendered, in various ways (video graphics, speech synthesis), to a human user. Various input apparatus are attached to the transmitting or other used instruments to provide control inputs to the computer.

System and method for augmentation of endoscopic surgery

A system for determining a position of a probe relative to an object such as a head of a body of a patient. The head includes a surface such as a forehead having a contour. Cross sectional images of the head are scanned and stored as a function of the forehead contour. If the forehead contour does not appear in the scan images, then the position of the forehead contour relative to the scan images is determined with an optical scanner and a ring. During surgery, the optical scanner also determines the position of the forehead relative to the ring. An array for receiving radiation emitted from the probe and from the ring generates signals indicating the position of the tip of the probe relative to the ring. A stereotactic imaging system generates and displays an image of the head corresponding to the measured position of the tip of the probe. The system may also display scan images from different scanning technologies which scan images correspond to the same position in the head.

System for indicating the position of a surgical probe within a head on an image of the head

The authors have developed an image-directed robotic system to augment the performance of human surgeons in precise bone machining procedures in orthopaedic surgery, initially targeted at cementless total hip replacement surgery. The total system consists of an interactive CT-based presurgical planning component and a surgical system consisting of a robot, redundant motion monitoring, and man-machine interface components. In vitro experiments conducted with this system have demonstrated an order-of-magnitude improvement in implant fit and placement accuracy, compared to standard manual preparation techniques. The first generation system described in this paper was used in a successful veterinary clinical trial on 26 dogs needing hip replacement surgery. It was the basis for subsequent development of a second-generation system that is now in human clinical trials. >

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An image-directed robotic system for precise orthopaedic surgery

The long-term success of cementless total hip arthroplasty (THA) may depend on bone ingrowth into the porous-fixation surfaces of the implant. The ingrowth process is facilitated when the surgeon achieves a satisfactory fit for the prosthesis. Clinically or roentgenographically visible failure and p

Development of a surgical robot for cementless total hip arthroplasty.

The invention is methods, systems and apparatus for planning the position of a prosthesis in a long bone in orthopaedic surgical procedures. A bone model (302) is generated from a scanned image of a bone, a prosthesis model (312) is selected from a library of prosthesis models (304) and then a cavity model (310) is formed based on the prosthesis model and/or the bone model. The cavity model may then be positioned over the bone model, either interactively by the surgeon or automatically through an algorithm based on clinical parameters, to determine a reasonable location for implantation of a prostehsis within the bone. The cavity model allows the surgeon to optimize placement of the implant within the bone, and it provides important clinical information to the surgeon, such as areas in which press fits are provided, extension areas for possible subsidence, and access areas for allowing the surgeon to insert the implant into the cavity.

System and method for cavity generation for surgical planning and initial placement of a bone prosthesis

The authors describe the use of force feedback in a surgical robot system (ROBODOC). The application initially being addressed is total hip replacement (THR) surgery, where the robot must prepare a cavity in the femur for an artificial implant. In this system, force feedback is used to provide safety, tactile search capabilities, and an improved man-machine interface. Output of the force sensor is monitored by a safety processor, which initiates corrective action if any of several application-defined thresholds are exceeded. The robot is able to locate objects using guarded moves and force control (ball-in-cone strategy). In addition, the force control algorithm provides an intuitive man-machine interface which allows the surgeon to guide the robot by leading its tool to the desired location. An application of force control currently under development is described, where the force feedback is used to modify the cutter feed rate (force controlled velocity). >

Force sensing and control for a surgical robot

Describes robotics and medical imaging technology in the enhancement of precision surgery. The authors consider: cementless total hip replacement application; system overview; ORTHODOC preoperative planning workstation; ROBODOC surgical assistant; safety features; surgical protocol. >

Joel Zuhars

Papers

An image-directed robotic system for precise orthopaedic surgery

Development of a surgical robot for cementless total hip arthroplasty.

System and method for cavity generation for surgical planning and initial placement of a bone prosthesis

Force sensing and control for a surgical robot

An integrated system for cementless hip replacement