“Stealth” technology could bring benefits of MRI to patients with medical implants

Researchers at the Martinos Center for Biomedical Imaging at Massachusetts General Hospital (MGH) have used a “cloaking” technique to redesign the wires within the cores of medical implant leads to reduce the dangers of heat-related injury from MRI in affected patients, according to a paper published online in Scientific Reports.

Radiofrequency energy resulting from MRI increases the electrical current induced in traditional metallic wires contained within many medical device leads, which can damage tissues with excess heat at the site of stimulation. While the FDA has approved several “MR conditional” devices, they are limited to use in low-power scanners that provide imaging quality far below that of traditional MRI, says lead author Peter Serano, MD, and his colleagues at MGH. “Approximately 300,000 patients with implanted or partially implanted medical devices are denied MRI each year because of safety concerns,” wrote Serano et al. “The lack of access to MRI is expensive to society because patients are denied the benefits of screening and accurate diagnosis.”

The researchers used resistive tapered stripline (RTS) technology to disrupt the increased current caused by radiofrequency energy, a technique similar to that used in stealth military aircraft technology. “After calculating the features required to produce an RTS lead that would minimize heat generation, the investigators designed and tested a deep-brain stimulation device with such a lead in a standard system used for MRI testing of medical implants—a gel model the size of an adult human head and torso. Compared with a commercially available lead, the RTS lead generated less than half the heat produced by exposure to a powerful MRI-RF field, a result well within current FDA limits,” read a news release from MGH.

Unlike CT imaging, MRI would allow doctors of patients with deep-brain stimulation implants to more accurately ensure that the stimulation signal is delivered to the appropriate tissues in the correct areas of the brain. But the technology doesn’t just impact deep-brain implants—it would also apply to any type of medical implant including pacemakers, defibrillators and spinal cord stimulators, according to Serano and his colleagues.  “[The RTS prototype] may easily replace any wire currently used in commercially available implant leads,” they wrote. “The results shown suggest the proposed design may allow a significant increase in the number of patients with medical implants having safe access to the diagnostic benefits of MRI.”