An MD&DI July 1997 Column
In the past few years, the use of virtual reality in medicine has been a hot topic for research. All this interest has generated advances in hardware and software and the discovery of several new applications.
In a decade of technological wonders, virtual reality (VR) has captured the public's imagination. And just as the public has dreamed of VR as the entertainment of the future, researchers in a variety of industries have also looked to it as a harbinger of monumental change. In universities, government institutions, and large and small companies, a great deal of attention and resources have been devoted to finding practical applications for this fantastical technology.
The Boston Dynamics, Inc., surgical simulator, incorporating a Phantom force-feedback interface from SensAble Technologies, Inc., allows a physician to feel as well as see virtual surgery.
VR is particularly suited to medicine, which can require the communication of complex, interrelated information to physicians in remote locations. Interest in improving telemedicine has actually spurred much of the research into VR. Last month's R&D Horizons column in MD&DI discussed many of the recent advances in telemedicine (see the May issue, page 96). As that article pointed out, without realistic vision, hearing, and even touch sensations, a remote physician will always be at a tremendous disadvantage in attempting to diagnose or treat patients.
The appeal that VR holds for medical researchers can be illustrated simply by the amount of material that has been written on it. Although medical VR is a relatively new technology, one Web site (http://hitl.washington.edu/projects/knowledge_base/medvr/) is already able to offer a survey of the literature and available resources on this subject that is 57 pages long.
Medicine Meets Virtual Reality, an annual conference that is held in San Diego, was started five years ago to cover this subject. The conference's growth has mirrored the growth of VR in medicine itself. In 1992, it drew 275 attendees, in the past two years about 750. According to Karen Morgan, the conference organizer, the number and type of exhibitors have also changed over the years. "In 1992, there were just a few tabletop exhibits, but now there are full-blown exhibits of products that are actually being used," says Morgan, adding that a lot of major companies have begun sending representatives to the conference to establish partnerships with smaller start-up firms.
In February 1994, MD&DI featured an article on VR and medicine (page 42). It concluded that "so much is still unknown about virtual reality that to make predictions about even its near-term prospects is to risk both underselling and overselling its potential." Given the tremendous amount of research into medical VR that has taken place since the article was written, it is time to consider whether that statement is still true.
Much of the recent press on medical VR has been generated by the use of VR to actually treat various conditions. These VR success stories have helped to personalize and publicize the technology.
In 1996, for example, an arachnophobic patient--who was dubbed MM, or Miss Muffet, to protect her identity--was successfully treated for a 20-year phobia in just three months with VR therapy. When she was referred by her doctor to the Human Interface Technology Laboratory, a joint research unit of the Washington Technology Center and the University of Washington (Seattle), MM had become so fearful of spiders that she had arranged her entire life to lessen the chance of encountering them. The HIT Lab, which was formed in 1989 with the goal of developing VR technologies into commercially viable products, built a virtual kitchen with a virtual spider lurking in it for MM's treatment. Gradually, MM was able to enter the SpiderWorld for longer and longer periods, and eventually even held a palm-sized toy tarantula as she interacted with the virtual spider. After only three months of treating her, researchers reported that MM was able to lead a normal life. Although MM's case was successful, using VR to treat phobias of this kind is an ongoing research effort.
Also in 1996, this time at the Medicine Meets Virtual Reality conference, HIT Lab associate Dave Warner of California's Loma Linda Medical School conducted a dramatic and successful teleconsultation with a patient suffering from a form of vertigo. In this demonstration, called The Bridge, the patient wore a headset that enabled Warner to monitor eye movement, which is a distinguishing characteristic of the disorder, as he treated the patient.
SIMULATION AND TRAINING
For all the excitement generated by such VR cures, most of the advances in medical VR have been in developing realistic simulations of medical procedures for training physicians or for helping them plan and carry out difficult operations.
With accurate anatomical data, the Center for Human Simulation has been able to develop surgical simulations.
These VR simulations can benefit the medical community in many ways. For example, they can lower the cost of training doctors by providing reusable patients that can be operated on repeatedly. They can provide assistance to doctors in performing difficult or complex procedures. They can reduce the need for animal experimentation. They can make medical information more accessible for remote consultations.
The success of these types of applications depends not only on the latest VR hardware and software, but also on accurate and voluminous medical data. Researchers at several sites have been gathering and processing such data for years, and their efforts are helping to make medical VR possible. For example, the National Library of Medicine (NLM) in Bethesda, MD, has been gathering data for its Visible Human Project for nearly a decade. The data sets, which consist of thousands of magnetic resonance imaging or computed tomography scans of cross sections of male and female cadavers as well as rendered anatomical slices of the cadavers, have been used in many VR simulations. The Center for Human Simulation (CHS) at the University of Colorado Health Science Center's School of Medicine (Denver) created the electronic data sets for the NLM. The CHS is presently continuing to process more anatomical data and also working on using the data in surgical simulations.
Much of the research in medical VR interfaces is taking place at universities and is being funded by the Department of Defense's Advanced Research Project Agency (DARPA). Research has also led to the development of several start-up firms. For inventors and individual entrepreneurs, VR offers tremendous opportunities as the demand for improvements in hardware and software grows. For larger manufacturers with investment capital, the technology offers an opportunity to buy licenses to mass produce what may prove to be the best-selling devices of the future.
With all this research, VR interfaces are rapidly becoming more realistic. The look of VR is constantly improving with advances in graphics and displays, as is its "feel" with the development of new force-feedback, or haptic, technology. It may not be very long before even the smell of medicine can be reproduced in a virtual environment.
One of the most promising new VR technologies involves the use of haptic interfaces, which have actually been studied on their own for decades, in conjunction with sight and sound VR stimuli. Touch is one of the most important cues for a physician; in fact, surgery is often conducted more by touch than by sight. In training, then, it is very important for a doctor to learn how an operation will feel.
One haptic interface that is gaining the attention of many in the medical industry is the Phantom, which was first developed as a senior thesis at MIT in 1993. The Phantom is a product of SensAble Technologies, Inc., and the software that controls it is produced by Boston Dynamics, Inc. (both of Cambridge, MA). It allows users to feel the physical properties of virtual objects while manipulating them to perform typical surgical operations, such as suturing broken tube structures in the body.
To use this device, a physician inserts his or her fingers into thimbles that are attached to a robotic arm, and then interacts with a virtual anatomy that is displayed on a computer monitor. The computer interprets the finger positions in 3-D space and returns the appropriate resisting force based on the physical properties of the virtual anatomy. Finger position is updated approximately 1000 times per second.
The Phantom can simulate not only resisting force but also smooth or textured surfaces, complex curves or sharp corners, and friction. The device provides feedback on the user's performance, measuring such variables as the amount of force applied or amount of contact between the physician's fingers and the patient's tissue.
The Phantom is already being used by several organizations to train physicians in some techniques. According to Thomas Krummel, MD, chairman of the department of surgery at Penn State (Hershey, PA), the Phantom will be used not only to train physicians, but also to test surgeons for certifications. The university has already purchased two of the devices.
Virtual retinal display eyeglasses from Microvision, Inc., will project images directly onto the back of the eye.
Using the Phantom, the Mitsubishi Electric Research Laboratory (MERL) in Cambridge, MA, along with Brigham and Women's Hospital, Carnegie Mellon University, and MIT, is developing a simulation of arthroscopic knee surgery. The system will include a computer model of the knee, a force-feedback device for haptic or tactile sensing of the virtual model, and real-time rendering of the knee model.
THE SIGHTS AND SMELLS OF THE FUTURE
The 3-D display technology used in virtual reality is also constantly being improved, as is the processing capability of the computers used to render the VR data.
Head-mounted displays are making it easier for a physician to observe VR while conducting operations. For example, the CardioView headset, produced by Vista Medical Technologies, Inc. (Carlsbad, CA), gives physicians data and ultrasound images of a patient's heart as they perform cardiac surgery.
An even more cutting-edge VR display is under development at Microvision, Inc. (Seattle). In this technology, called virtual retinal display (VRD), images are scanned directly onto the back of the eye with red, green, and blue streams of light. The user sees a 3-D image that appears to float a few feet away. The goal of the project, which was begun in 1993, is to develop a VRD that can be incorporated into a pair of eyeglasses (as shown above).
This new display, according to researchers, allows 20/20 vision, and is brighter than images created with other displays. It can even be seen by patients with some forms of partial vision loss.
As they create truly realistic VR, researchers are even taking the sense of smell into account. Smell can be an important part of diagnostics. For example, some mice have been able to smell a tumor-producing virus in patients even before tumor growth. Also, breath odor has been used to detect particular bacteria. In one project presently being funded by DARPA, the Artificial Reality Corp. (Vernon, CT) is attempting not only to study the effect of smell in surgical training, but also to develop a delivery system for virtual odors.
THE VIRTUAL HOSPITAL
As researchers keep finding practical applications for VR in medicine, it is becoming clear that this technology will be a major part of the hospitals of the future. In fact, some hospitals of the future may exist only in VR.
In this HIT Lab's virtual emergency room, the physician can customize the placement of patient data in 3-D space.
Researchers at the HIT Lab, for example, are developing a virtual emergency room that will be used for training physicians. This virtual world is based on the trauma center at Harborview Medical Center in Seattle. HIT Lab researchers are using photographs of the trauma center to develop the 3-D world for this project, which is called the Laboratory for Integrated Medical Interface Technology (LIMIT).
In this environment, patient data float freely, allowing the physician to customize his or her view for maximum convenience. For example, the doctor can drag a window over any part of the patient's body to immediately see an x-ray image of that area. Other vital charts can hang anywhere in the room.
At Children's Hospital in Boston, MERL is developing a virtual environment in which young patients can lessen their fears by taking virtual tours of the hospital or even the human body.
These projects are in relatively early stages of development, and completion will require a great deal of work. Although these virtual hospitals are not yet a reality, the popularity of medical VR as a research subject promises that advances in the technology will continue, and such futuristic applications may soon be realized.