Virtual Surgery
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INTRODUCTION
Rapid change in most segments of the society is occurring as a result of increasingly more sophisticated, affordable and ubiquitous computing power. One clear example of this change process is the internet, which provides interactive and instantaneous access to information that must scarcely conceivable only a few years ago.
Same is the case in the medical field. Adv in instrumentation, visualisation and monitoring have enabled continual growth in the medical field. The information revolution has enabled fundamental changes in this field. Of the many disciplines arising from this new information era, virtual reality holds the greatest promise. The term virtual reality was coined by Jaron Lanier, founded of VPL research, in the late 1980’s. Virtual reality is defined as human computer interface that simulate realistic environments while enabling participant interaction, as a 3D digital world that accurately models actual environment, or simply as cyberspace.
Virtual reality is just beginning to come to that threshold level where we can begin using Simulators in Medicine the way that the Aviation industry has been using it for the past 50 Years — to avoid errors.
WHAT IS VIRTUAL SURGERY?
Virtual surgery, in general is a Virtual Reality Technique of simulating surgery procedure, which help Surgeons improve surgery plans and practice surgery process on 3D models. The simulator surgery results can be evaluated before the surgery is carried out on real patient. Thus helping the surgeon to have clear picture of the outcome of surgery. If the surgeon finds some errors, he can correct by repeating the surgical procedure as many number of times and finalising the parameters for good surgical results. The surgeon can view the anatomy from wide range of angles. This process, which cannot be done on a real patient in the surgery, helps the surgeon correct the incision, cutting, gain experience and therefore improve the surgical skills.
The virtual surgery is based on the patient specific model, so when the real surgery takes place, the surgeon is already familiar with all the specific operations that are to be employed.
TRAINING AND EDUCATION
The similarities between pilots and surgeons responsibilities are striking; both must, be ready to manage potentially life-threatening situations in dynamic, unpredictable environments. The long and successful use of flight simulation in air and space flight training has inspired the application of this technology to surgical and education.
Traditionally, textbook images or cadavers were used for training purposes, the former ie textbook images, limiting one’s perspective of anatomical structures to 2D plane and the latter, cadavers; limited in supply and generally allowing one-time use only. Today VR simulators are becoming the training methods of choice in medical schools. Unlike textbook examples, VR simulators allow users to view the anatomy from a wide range of angles and “fly through” organs to examine bodies from inside.
SURGICAL PLANNING
In traditional surgery planning, the surgeon calculates various parameters and procedure for surgery from his earlier experience and
imagination. The surgeon does not have an exact idea about the result of the surgery after it has been performed. So the result of the surgery depends mainly on human factors. This leads to lots of errors and even to the risk of losing the life of the patients. The incorporation of the virtual reality techniques helps in reducing the errors and plan the surgery in the most reliable manner.
‘The virtual reality technology can serve as useful adjunct to traditional surgical planning techniques. Basic research in image processing and segmentation of computed tomography and magnetic resonance scans has enabled reliable 3D reconstruction of important anatomical structures. This 3D imaging data have been used to further understand complex anatomical relationships in specific patient prior to surgery and also to examine and display the microsurgical anatomy of various internal operations.
IMAGE GUIDANCE
The integration of advanced imaging technology, image processing and 3D graphical capabilities has led to great interest in image guided and computer-aided surgery. The application of computational algorithm and VR visualization to diagnostic imaging, preoperative surgical
planning and interaoperative surgical navigation is referred to as Computer Aided Surgery. Navigation in surgery relates on stereotatic principles, based on the ability to locate a given point using geometric reference. Most of the work done in this field has been within neurosurgery. It also proved useful in Robotic Surgery, a new technique in which surgeon remotely manipulate robotic tool inside the patient body. An image guided operating robot has been developed Lavellee et al, and Shahide et al have described a micro’ surgical guidance system that allows navigation based on a 3D volumetric image data set. In one case, we use intra operative mapping of 3D image overlays on live video provides the surgeon with something like ‘X-ray vision’. This has been used in conjunction with an open MRI scan to allow precise, updated views of deformable brain tissues. Other researchers have focused on applications for orthopedic procedures. Improvements in sensor and imaging technology should eventually allow updates of patient’s position and intra operative shape changes in soft tissues with in reasonable time frame.
3D IMAGE SIMULATION
The first step in this is to generate a 3D model of the part of the body that undergo surgery Simulating human tissues-beit tooth enamel, skin or blood vessels-often starts with a sample from a flesh and blood person that is we should have a 3D model of the part of the body. Using computer graphics we first construct a reference model. Depending on this simulation needed, anatomical images can be derived from a series of patient’s Magnetic Resonance Images (MRI), Computed Tomography (CT) or video recording, which are 2D images. These images are segmented using various segmentation methods like SNAKE’. The final model is obtained by deforming the reference model with constraints imposed by segmentation results. The image is digitally mapped on to the polygonal mesh representing whatever part of the body on organ is being examined. Each vortex of the polygon is assigned attributes like colour and reflectivity from the reference model.
TOUCH SIMULATION
The second step in the simulation of surgery is simulating haptic-touch sensation. Physicians rely a great deal on their sense of touch for everything from routine diagnosis to complex, life saving surgical procedure. So haptics, or the abili to simulate touch, goes a long way to make virtual reality simulators more life like.
It also add a layer of technology that can stump the standard microprocessor. While the brain can be tricked into seeing seamless motion by flipping through 30 or so images per second, touch signals need to be refreshed up to once a millisecond. The precise rate at which a computer must update a haptic interface varies depending on what type of virtual surface is encountered-soft object require lower update rates than harder objects.
A low update rate may not prevent a users surgical instrument from sinking into the virtual flesh, but in soft tissues that sinking is what is expected. If we want something to come to an abrupt
stop that is in the case of born, etc it requires a higher update rates than bumping into something a little squishy like skin, liver etc.
CONCLUSION
Medical virtual reality has come a long way in the past 10 years as a result of advances in computer imaging, software, hardware and display devices. Commercialization of VR systems will depend on proving that they are cost effective and can improve the quality of care. One of the current limitations of VR implementation is shortcomings in the realism of the simulations. The main Impediment to realistic simulators is the cost and processing power of available hardware. Another factor hindering the progress and acceptability of VR applications is the need to improve human-computer interfaces, which can involve use of heavy head-mounted displays or bulky VR gloves that impede movement. There is also the problem of time delays in the simulator’s response to the users movements. Conflicts between sensory information can result in stimulator sickness, which includes side effects such as eyestrain, nausea, loss of balance and disorientation. Commercialization of VR systems must also address certain legal and regulatory issues.