Warren J. Viant

Image guided orthopaedic surgery design and analysis

Within the next few years it is envisaged that a number of computer assisted surgery products will become available. For many surgical procedures, outcome of surgery,, will rely on the accuracy and repeatability with which a computer assisted surgical toolperforms its task. This paper presents a Computer Assisted Orthopaedic System (CAOS) which takes an image guided approach to planning and implementing a trajectory, to assist an orthopaedic surgeon. Accurate delivery of this trajectory is achieved via an intelligent guide. This paper details the design issues and identifies the registration and calibration techniques used by the CAOS intelligent guide. The paper also enumerates, and where possible quantifies, thefactors that influence the accuracy performance of the system. Accuracy trees are used to show the root source of inaccuracies and how they propagate and combine in a system.

Implicit Fitting Using Radial Basis Functions with Ellipsoid Constraint

Implicit planar curve and surface fitting to a set of scattered points plays an important role in solving a wide variety of problems occurring in computer graphics modelling, computer graphics animation, and computer assisted surgery. The fitted implicit surfaces can be either algebraic or non‐algebraic. The main problem with most algebraic surface fitting algorithms is that the surface fitted to a given data set is often unbounded, multiple sheeted, and disconnected when a high degree polynomial is used, whereas a low degree polynomial is too simple to represent general shapes. Recently, there has been increasing interest in non‐algebraic implicit surface fitting. In these techniques, one popular way of representing an implicit surface has been the use of radial basis functions. This type of implicit surface can represent various shapes to a high level of accuracy. In this paper, we present an implicit surface fitting algorithm using radial basis functions with an ellipsoid constraint. This method does not need to build interior and exterior layers for the given data set or to use information on surface normal but still can fit the data accurately. Furthermore, the fitted shape can still capture the main features of the object when the data sets are extremely sparse. The algorithm involves solving a simple general eigen‐system and a computation of the inverse or psedo‐inverse of a matrix, which is straightforward to implement.

Desktop-based computer-assisted orthopedic training system for spinal surgery.

BACKGROUND Simulation and surgical training has moved on since its inception during the end of the last century. The trainees are getting more exposed to computers and laboratory training in different subspecialties. More needs to be done in orthopedic simulation in spinal surgery. AIMS To develop a training system for pedicle screw fixation and validate its effectiveness in a cohort of junior orthopedic trainees. TRAINING SYSTEM Fully simulated computer-navigated training system is used to train junior orthopedic trainees perform pedicle screw insertion in the lumbar spine. Real patient computed tomography scans are used to produce the real-time fluoroscopic images of the lumbar spine. MATERIAL AND METHODS The training system was developed to simulate pedicle screw insertion in the lumbar spine. A total of 12 orthopedic senior house officers performed pedicle screw insertion in the lumbar spine before and after the training on training system. The results were assessed based on the scoring system, which included the amount of time taken, accuracy of pedicle screw insertion, and the number of exposures requested to complete the procedure. RESULTS The result shows a significant improvement in amount of time taken, accuracy of fixation, and the number of exposures after the training on simulator system. This was statistically significant using paired Student t test (p < 0.05). CONCLUSION Fully simulated computer-navigated training system is an efficient training tool for young orthopedic trainees. This system can be used to augment training in the operating room, and trainees acquire their skills in the comfort of their study room or in the training room in the hospital. The system has the potential to be used in various other orthopedic procedures for learning of technical skills in a manner aimed at ensuring a smooth escalation in task complexity leading to the better performance of procedures in the operating theater.

A Phantom Based Approach to Fluoroscopic Navigation for Orthopaedic Surgery

The use of the C-arm fluoroscope for surgical navigation in various Computer Assisted Orthopaedic Surgery Systems (CAOS) has been an important success of research into CAOS technology. To use the fluoroscope for quantitative surgical navigation involves calibrating its 2D images and tracking the spatial position of the fluoroscope’s image beam. This allows 3D reconstruction of anatomy from a series of 2D fluoroscopic images. This paper presents a new technique for determining the C-arm position and calibrating the image beam. This technique is based on a small imaging phantom that is placed close to the patient. This paper also briefly describes the CAOS system developed at Hull that uses this imaging phantom and reports on in vivo and in vitro studies.

Recovery of distal hole axis in intramedullary nail trajectory planning

In intramedullary nail (IMN) surgical operations, one of the main efforts for surgeons is to find the axes of two distal holes. Two distal holes on an intramedullary nail, which are inside the intramedullary canal of a patients femur, can only be seen in a lateral X-ray view. For the standard surgical procedure, the localisation of the distal hole axes is a trial-and-error process which results in a long surgical time and large dose of X-ray exposure. In this paper, an algorithm to derive the 3D position and orientation of the distal hole axis was developed. The algorithm first derives the nail axis through two X-ray images. Then the distal hole axis is calculated through projecting back the hole boundary on the X-ray image from a lateral view to the 3D space. A least squares method is used to determine the centres of the front hole and the back hole through iteration. The algorithm has been tested with real data and it was accurate and robust.

End user issues for computer assisted surgical systems

Orthopaedic implants are manufactured to the highest degree of precision by some of the most precise machines known to man and inserted into patients by some of the most imprecise methods known. Computer assisted systems aim to overcome this dichotomy by improving the planning and implementation of orthopaedic surgery. This can be achieved by providing the surgeon with better information for planning and a more precise means of implementing the surgery. This surgical advancement will change current orthopaedic practice significantly if the appropriate surgical issues are considered during their development. Safety is obviously paramount and is being addressed, as is registration between the real (patient) and the virtual computer world. The more subtle, but nevertheless important, surgical issues have as yet not been fully identified or addressed satisfactorily. The following questions serve to highlight them. Is there an optimal system size, shape, reach, control and positioning in surgery? What are the salient environmental and functional requirements ? Can there be intra-operative computer processing time? How important and what does timelessness, universality, communality and simplicity of the system mean? Should there be a relationship between training, surgical feedback and simplicity? What is partial or total sterilisation ? Can capital outlay and running costs for the system be reduced or avoided by the hospitals? Are computer assisted orthopaedic surgical systems cost effective, necessary, desirable or indeed indicated in current cost containment in the NHS? The above questions are answered in this paper and points which are conducive to a positive response from the end user (surgeons, and hospital management) are discussed.

New perspectives on ancient landscapes: a case study of the Foulness valley

The standard method for gathering and representing archaeological information consists of two-dimensional layer managers. This paper presents an archaeological Geographical Information System (GIS) based on an immersive virtual environment. Our goal is to provide an immersive visualisation of multiple datasets relating to the Foulness Valley in East Yorkshire. By maximising the users visual bandwidth within an immersive virtual environment, we have provided archeologists with greater insight into the Foulness Valley datasets using both existing and novel visualisation tools and techniques.

Serious games for Fire and Rescue training

The Incident Commander plays a vital role in the effectiveness of the UKs Fire and Rescue Services, in tackling fires. The reduction in the number of incidents along with budget cuts is placing an increased emphasis on training. In this paper we propose a serious game as a replacement for the tradition training methods for these important command positions, with a discussion of immersion versus more traditional platform.

A mathematical model for acquiring a cone axis from X-ray images

This paper describes the mathematics of acquiring a cone axis through the projection of its conical boundary from X-ray images. A thorough analysis and rigorous proofs are presented for a better understanding of this basic problem. The results can be directly used for the trajectory planning of sliding hip screw and IntraMetullary nail operations by the computer assisted orthopaedics surgical systems.