TROY, N.Y. — It's hard to stitch closed a wound for the first time.
It can take a few tries to stick the needle into the skin close enough to the injury.
And feeling the skin tug when you draw out your line is disconcerting — even if you're just manipulating a simulation on a computer screen, even if the “tug” is produced by a mechanical arm mimicking the springy resistance of flesh.
The stitch job described above took place in virtual reality, performed on a simulator being developed at the Rensselaer Polytechnic Institute. Surgical instruments move in 3-D on a computer screen, mirroring the movements of a stylus attached to the mechanical arm. Novices can experience what it's like to close a wound or use a scalpel, minus the risk of grave consequences.
Surgical simulators are commonly used in training already. But RPI professor Suvranu De said his prototype — in which the tactile qualities of organs are simulated in real time through mathematical equations and software — represents the next generation. With this technology, surgery could be practiced on home computers. Down the line, Mr. De hopes researchers in haptics — the science of touch — could also use the technology to create a “palpable human,” a database of the physical characteristics of every bone, joint and organ in our body.
“The technology we're using is far beyond what is out there,” said Mr. De, director of the Advanced Computational Research Lab at RPI.
For generations, medical students learned surgical techniques by observing and practicing on cadavers and animals. Over the past 15 years, those methods have been complemented more often by simulators that provide a way to teach procedures like catheterizing a vein or managing an airway.
Some training aids are mannequins that simulate the workings of the human body, complete with working airways and blood pressure. Others create a virtual reality; users look at a computer screen while working on a model.
Mr. De claims his simulator is better because there are no physical objects being sliced or poked. Plastic and springs simply can't reproduce the soft give of a lung or liver, nor can they reproduce the complicated interaction of internal organs when people breathe, he said.
“They'll be squishing against each other,” said Mr. De. “Nothing stays static when you're breathing.”
Mr. De is among the small group of researchers trying to represent the physical qualities of organs through algorithms. Once he crafted the equations, Mr. De's team methodically mapped the physical characteristics of internal organs, relying on data from cadavers and live pigs, which are frequently used in medical experiments.
The algorithms rule the reactions of the simulator's articulated arm, which looks a bit like a tiny desktop swivel lamp. Movements of the stylus — up, down, forward, backward, angled — are reproduced on the screen. Prod a bone, your stylus is stopped cold. Prod the adjacent muscle, you feel a springy resistance.
“It is the cutting edge of virtual simulation,” said Dr. Paul E. Phrampus, interim director of the Peter M. Winter Institute for Simulation, Education & Research at the University of Pittsburgh Medical Center.
Dr. Phrampus, who is not involved in the RPI project, said only a small number of researchers worldwide have demonstrated algorithm-dependent simulators. He said machines that reproduce the sense of touch are much more difficult to make than devices focused in re-creating a visual experience, like flight simulators.
David Hananel of METI, a simulator company collaborating with Mr. De, said there are relatively few algorithm-dependent simulators on the market now because of the tremendous amount of calculations required to give real-time feedback. Mr. De's algorithms are designed to draw less computational power.
Despite the difficulties, Dr. Phrampus expects the number virtual reality systems to grow because they can train doctors, combat medics and other medical professionals for less money. While mannequins can cost $40,000 to $250,000, software-based simulations should be inexpensive enough for a mass market, he said.
Mr. De hopes to create a simulator that would cost about $10,000.
Mr. De is the first year of a four-year $1.4-million grant from the National Institutes of Health. Residents at Albany Medical Center will begin testing the simulator this fall. Residents at Beth Israel Deaconess Medical Center in Boston also will soon be involved in testing, Mr. De said.
It will take considerably longer to create a “palpable human.” While there are detailed maps of what the body looks like inside thanks to MRI and CT scans, there is far less data on what our insides feel like or, more precisely, how they respond to touch.
Mr. De said such a database would be useful not only for training, but for surgical planning. Surgeons could test tricky procedures on the computer, perhaps seeing which artery graft works the best.
Dr. Phrampus is similarly bullish on virtual reality, believing that surgical procedures are likely to be simulated on devices similar to Playstations one day. But he doubts that it will ever entirely take the place of hands-on training.
“There are other things where you physically need to get your hands on two places in a physical space,” Dr. Phrampus said.
