(NASA - May 31, 1996) A simple robot that can "learn" the physical characteristics of the brain soon may give surgeons finer control of surgical instruments during delicate brain operations.
In a new procedure being developed at NASA's Ames Research Center, Mountain View, CA, a robotic probe will "learn" the brain's characteristics by using neural net software, which is the same type of software technology that helps focus camcorders. The probe, equipped with a tiny pressure sensor, will enter the brain, gently locating the edges of tumors while preventing damage to critical arteries.
"Potentially, the robot will be able to 'feel' brain structures better than any human surgeon, making slow, very precise movements during an operation," said principal investigator Dr. Robert W. Mah of the NeuroEngineering Group at Ames. Brain tumors typically have a different density than normal brain tissue. This difference allows neurosurgeons to find the tumor's edge through experience.
"NASA's Neurosurgical Computational Medicine Testbed is a unique and essential element in our goal to improve the safety, accuracy and efficiency of neurosurgery," said Dr. Russell J. Andrews of the Veterans Affairs Palo Alto Health Care System and clinical associate professor of neurosurgery at Stanford University. "This collaboration is a good start toward meeting that goal." Mah has worked with Andrews since 1994 to develop the smart robot.
The probes used on the robot are much smaller than standard probes, and should further reduce potential brain damage. During standard brain surgery, the surgeon uses a magnetic resonance image [MRI] to guide placement of the probe in the brain. The physician samples the tumor by inserting a biopsy probe through an opening in the skull.
"A probe can be as large as 0.2 inches in diameter," Mah said. "As it enters the brain, there may be injury to brain tissue. If an artery is damaged as the doctor inserts the probe, the patient could bleed to death," Mah said.
In contrast, during the robotic neural net procedure, the speed and maximum pressure are controlled by a "smart" computer program that continues to learn as it gains more experience. If it hits an artery, the probe will stop before it penetrates. If the computer stops the probe, the surgeon can decide what to do next.
"Besides having robotic computer control, we have miniaturized everything. Instead of a probe that is almost 0.2 inches in diameter, all we need is a probe about one-third that size," Mah said. "That minimizes brain damage, too." A biopsy needle extracts a tissue sample through the probe.
Ames is developing robotic telepresence surgery to deal with medical emergencies that may occur during long-duration human space flights. "On a long-duration mission, there likely won't be a medical specialist on board to deal with a specific surgical problem," Mah said. "A surgeon on Earth could control the surgery by issuing high-level commands, such as 'start surgery' or 'take sample' to the robot. The computerized robot would go as far as it could within safe limits. Then it would wait for the next command from Earth."
During early tests, scientists used tofu, a food made from soybeans that has a consistency very similar to brain tissue, to model tissue types. "These tests were used to teach the neural net software what are normal brain tissues and arteries and what are not," Mah said.
The software learns to distinguish tumors from normal brain tissue by remembering the pressure signatures or profiles for each kind of tissue, and then making a model. Using traditional computer programming to do the brain modeling job is not practical. "It is very difficult to model the human brain. A human computer programmer would have to mathematically model each patient and each kind of tissue," Mah added.
A modified form of the brain surgery robot could be used for other kinds of surgery. "It could be used in the kinds of surgery that can use 'smart' sensors. Besides pressure sensors, there are sensors that can detect temperature, acidity and the amounts of various kinds of chemicals," he said.
Original file name: .CNI - Robot Brain Surgeon 6.3
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