A curved robotic needle that weaves its way through the brain in a needle-sized path may help combat one of the most lethal kinds of stroke, intracerebral hemorrhage.
Stroke is a killer, the second leading cause of death globally, and one of the leading causes of disability. Intracerebral hemorrhage, where leaked blood from a ruptured vessel pools in the brain, accounts for ten to twenty percent of all strokes and is especially deadly. Medical literature reports a 30-day mortality rate of 43 percent, with half of the deaths occurring during the acute phase.
Treating intracerebral hemmorage is dicey, as a neurosurgeon must open the skull and penetrate the brain to find and access the hematoma. It’s risky surgery, because healthy brain tissue may be destroyed in the process. Depending on the location in the brain, that could cause problems ranging from amnesia to loss or disruption of motor control.
Researchers at Vanderbilt University are working on an alternative, a curved robotic needle that weaves its way through the brain in a needle-sized path to the clot, where it can aspirate the hematoma. For greater accuracy, it is designed to work within a magnetic resonance imaging machine and allow a surgeon to guide the device to the clot using real-time imaging.
Working within an MRI machine is difficult because its strong magnetic force prevents the use of traditional metal tools or equipment. Yue Chen, a mechanical engineering doctoral student at Vanderbilt’s Medical Engineering and Discovery Lab and the Laboratory for Design and Control of Energetic Systems, and team members solved that problem by designing and manufacturing the device using plastic and materials that aren’t affected by the magnetic force.
“Most of it is plastic, with some aluminum [and brass] and it is MRI compatible,” says Yue. “Other metals are not safe.”
Yue says the device includes a robot that actuates the tubes with air pressure and an aiming device to point the robot in the proper direction. A tracking marker at the tip of the aspirating tube provides feedback on positioning during the operation. Using real-time images, the surgeon can direct the device through or around brain deformations and steer the needle to the clot. Upon arrival, the needle breaks up the hematoma and evacuates it.
Yue used a Stratasys 3D printer to fabricate the device, which includes what he says is a novel type of pneumatic Pelton turbine motor. Pneumatic systems are important for the application because they do not generate a magnetic field that would interfere with an MRI machine.
During tests with a bottle phantom, the device was connected to a control device in an adjoining room using an air hose and optical fibers. The positional accuracy of the needle tip corresponded with its kinematic model, and Yue says the device was used to successfully remove a clot in a sheep’s brain.
“The idea behind this is to try to deal with ICH in a different manner,” says Yue. “The conventional method is to open the skull. This is not beneficial to all patients, so we are proposing a noninvasive method accessing the brain through a two-millimeter-sized hole.”
More testing is needed—the next step is to use the robot on a cadaver—but that depends on winning more funding. Yue believes the device holds commercial promise for a couple of reasons: it is disposable and cheap, costing in the neighborhood of $50 to produce. The team has obtained patents on the mechanical design of the robot and the curved, hollow needle.
Yue’s device, developed under the direction of ME Associate Professor Robert Webster, is not the laboratory’s first effort. An earlier robot employs a bellows-type design with flexible actuators using a stepper mechanism. Eric Barth, an associate professor in the school’s DCES lab, says the “grasp and release” control sequence of the motor “has certain advantages such as being inherently safe and hermetically sealed.” The newer one is not in any sense better than the old and Barth says Yue’s design is his own, developed earlier at the University of Georgia under the guidance of Professor Zion Tsz Ho Tse.
The Vanderbilt lab also is using the curved needle concept in attempts to treat epilepsy, under the direction of Barth. Researchers note that medication fails to help some 30 percent of patients reduce or eliminate seizures. In some cases, surgeons open the skull and remove a lesion of the brain that is the source of the seizures. That brings the risk of impairment if too much tissue is removed.
Another treatment method has the surgeon drill a hole and, using magnetic resonance imaging, place a probe in the affected area and ablate it using a laser. But if the affected area is curved, there is still a chance that ablation will not cover the entire lesion.
Yue and the Vanderbilt team want to use the curved needle concept to deliver a probe, noting that its potential to follow a curved or winding path to the area promises greater success. “We’re trying to use helical ablation to destroy the cells in the hippocampus, using a one-millimeter needle,” says Yue.
He says the MRI machine provides a guide because the imaging will show how much tissue is being destroyed. “You use the image to tell how much tissue is cooking,” he says. “We don’t want to overcook.”
Yue says the device will be tested on a cadaver in a few months.
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