Making surgical simulation real

Introduction Simulation-based surgical training has phenomenal potential to improve medicine and the health of mankind. Through simulation, medical personnel can practice standard procedures over and over. Gone will be the days of visually and physiologically limited plastic and rubber models. The cost, difficulty and health implications of using cadavers will also be lessened. Most important, patients will no longer serve as the best source for teaching opportunities. But the implications of surgery simulation go beyond normal surgical practice.Techniques to handle unique pathologies and complicarJons will be available to others besides the small subset of specialists who, until now, have had training at a limited number of large medical centers where such cases are particularly prevalent. Surgical procedures which are nearly impossible to train for at present (such as treatment of massive explosive-related trauma, unusual in civilian life, but all too common in the bardefield), can be acquired through simulation. The greatest achievement wi l l be the ability to rehearse an individual~ surgery using models derived from their MR, CT or ultrasound images. Surgeons wil l be familiar wi th the inevitable unique characteristics of the patient's anatomy before they begin the first incision. Wi th all the progress in virtual environmeats and flight and vehicle simulation technology, what is the state of medical simulation! Medical simulation-based training is a growth industry with many opportunities and a number of technical challenges.Work has been presented to date showing significant progress in a number of areas. This progress is benefiting from existing flight simulation technology as well as increased interest from traditional proPonents of simulation such as those involved in defense training. Surgical simulations, however, differ in significant ways from flight and vehicle simulators. In surgical simulation, the user is typically focusing on interacting with the objects in the simulation while parr of the objecuve OF flight and vehicle simulation users is to not contact other objects. The emphasis on interacting with a deformable environment in surgery, rather than navigating about in a rigid one in flying, requires very different mathematical modeling techniques from those used in previous simulators. Entities in flight and vehicle simulators are typically not interdependent while in surgical simulators they often are. For instance, when a plane has a malfunction it will usually affect only the plane itself and not the other planes in the same flight area. It is typical in a surgical simulator for the cucUng of tissue to have local or systemic effects which change both the current behavior and the possible response of other tissues to future user interaction. To make the simulations tractable, early commercial pioneers, such as HT Medical (formerly High Techsplanations), have focused on simplifications of procedures which can benefit from simulation-based training. These are primarily techniques which are performed with instruments and whose actions are viewed through a computer or television display. Simulation of these procedures allows the instrument actions to be sensed and sent to the simulation system which in turn renders the effect of the instrument on a computer display. In addition, the forces of tools on the anarorny are fed back to the simulation usecThus, to the user it can be a real procedure; the hand actions are the same, the feel is the same, and the visuals are the same. Nothing is different for them, but the patient is replaced with a simulation. In addition to these instrument and display intensive procedures, HT Medical has developed simulations that use physical models derived from medical scanner data to represent the external surface of a padent coupled with force feedback devices to render contact loads. This approach is ideal for simulating venous access, a typically two handed process where needles are placed into vasculature.These procedures focus as much on the feel of needle as it slides into place as they do on the selection of the site and proper needle orientation at insertion. Lastly, fully immersive, augmented reality simulations for battlefield trauma treatment training are under development.These combine tactilely realistic, physical models with tracking hardware and virtual studio technoleey to provide the trainee with hands-on experience in evaluating abdominal wounds. This combines a number of proven technologies in a unique manner yielding an environment which enables training for situations for which it has never been previously possible to train. Creation OF these medical procedural simulations requires more than the replication of the visual characteristics of anatomical structures.The physical response of tissue to instruments, such as deformation from being rasped by forceps or cutting of the tissue surface by a scalpel, must be modeled. Individual physical dssue behaviors must be ded to the surrounding tissues to properly model collateral effects. Physical modeling is also critical for correct visual and haptic response to user action. More important than these physical behaviors, there must exist a systemic control system which ties physiological reactions co local user actions, as well as autonomously initiamd activities to the simultaneous immediate and longer term responses of other bodily structures. The key component of the simulation beyond such modeling derails is that the content of the simulation must be developed in conjunction with experts in each surgical field to assure proper replication of the procedure.