Last fall, Dr. Aviva Abosch, associate professor in neurosurgery in the CU School of Medicine, had a problem. She found that while preparing for deep brain stimulation (DBS) surgery on patients who suffer from tremors, whether from Parkinson’s disease or other causes, it was difficult to get a good, quality image during a preoperative MRI or CT scan. She approached Christopher Yakacki, assistant professor in mechanical engineering, for a solution.
“Dr. Abosch asked if we could design and manufacture an adjustable adapter that attaches to the MRI table and secures the head frame on the patient to prevent any movement caused by tremors,” says Yakacki, whose research focuses on smart materials for biomedical devices. “Currently, no manufacturer produces this type of adapter.”
According to Abosch, DBS has become the standard of care for the treatment of movement disorders such as Parkinson’s disease. DBS surgery involves the implantation of an electrode into a precise target in the brain that serves as a node in the control of function—for example, the control of movement in the case of Parkinson’s disease. These targets are very small, measuring less than 1 cm in diameter, and they are situated approximately 9 cm from the brain’s surface.
Because of the complex location of these targets, surgeons use a technique known as stereotaxy to determine the placement of the node. Stereotaxy is based on the premise that all points in three-dimensional space can be defined by an x, y and z coordinate.
To prepare for DBS, a head frame, which serves as a coordinate system, is attached to the patient. Then, through an MRI or a CT scan, imaging of the patient’s brain in this frame is obtained and the x, y, and z coordinates of the target structure are determined. These coordinates allow the neurosurgeon to place the tip of the DBS electrode into the brain target. To achieve the best image possible, the patients need a head restraint during the MRI or CT scan—something to connect the existing brace to the table.
“Any movement of the patient’s head during stereotactic imaging, i.e., an MRI and CT of the brain in the head frame, can lead to inaccuracies of the target coordinates,” says Abosch. “This, in turn, results in the DBS electrode being placed in the wrong location in the brain, resulting in side effects or diminished efficacy.” The development of this new adapter would greatly reduce the chance for movement during the imaging process.
“When Dr. Abosch and I first discussed this project, I estimated that it would take approximately three to four months to complete,” says Yakacki. “However, she explained there was an immediate need for the device and would like it in three to four weeks.” To complete this project so quickly, Yakacki turned to two mechanical engineering students for help: Eric Losty, a senior, and Sean McDonough, a graduate student.
“I chose Eric and Sean for their individual strengths and skill sets,” says Yakacki. “Sean does really well with design, and Eric has great machining skills.”
Losty and McDonough met with Abosch and her team to get measurements of the MRI table and the existing head frame. They used rapid prototyping techniques, such as laser cutting and three-dimensional printing, to test their designs quickly.
“We started with one design, but had to make minor changes once we began machining the parts,” says McDonough. “We went with a modular design that breaks down into pieces,” adds Losty. “That way, it’s easier to machine, test and iterate on the design, if needed.”
Because of the nature of the imaging process, there were some limitations and challenges to developing a solution.
“MRIs use magnetic waves, which limits the materials that can be used for such an apparatus,” says Losty. “The final product is made with aircraft-grade aluminum, titanium and brass.” Other challenges included creating a system that was lightweight yet robust enough to prevent movement in a patient with a significant head tremor. The students were able to perform stress analysis tests through their SolidWorks design software.
The project took just over 100 hours to complete, and was finished within a month. The adapter has been used successfully in more than a dozen DBS cases to date. In January, the University of Colorado Technology Transfer Office filed a patent application for the adapter designs. In February, Losty and McDonough also designed and built a similar adapter for the CT scan table, and those concepts are also covered in the patent application filed by the university.
Abosch and Yakacki plan to continue their collaboration and develop solutions for pediatric DBS. “Projects like these are great opportunities to build relationships with the CU School of Medicine,” Yakacki says. “They also enable our students to work on interdisciplinary projects in a way that advances their education beyond the classroom.”
Yakacki believes this project is a prime example of CU Denver becoming a premier institution. “The rate at which this project was completed is unprecedented in my experience,” says Yakacki. “I don’t think that there is a group in America, either in academia or industry, that could design and manufacture a medical device faster than we did.”
Editor’s note: In March, Children’s Hospital Colorado approved a one-year stipend for Sean McDonough to continue making these devices, and potentially more, for pediatric deep brain stimulation cases.