By Aine Cryts

Getting an MRI can be a stressful experience. Joseph Rispoli, PhD, assistant professor at the Weldon School of Biomedical Engineering at West Lafayette, Ind.-based Purdue University, knows that personally. Rispoli admits that he tried to ramp up his marathon training too quickly, and it led to a stress fracture. That meant he had to get an MRI, which “highlighted the fracture clearly,” he tells AXIS Imaging News.

“Not as comfortable of an experience as it could be.” That’s how Rispoli describes his experience in the MRI gantry. That drove him to help develop with a team of Purdue University researchers the stretchable, wearable coils that make the experience easier on patients. AXIS Imaging News recently interviewed Rispoli about this technology, which is now in prototype form.

AXIS Imaging News: The material in the stretchable, wearable coils is similar to what’s used in the aerospace and defence industries. Tell us more.

Joseph Rispoli: The aerospace and defense industries have driven the development of a number of new materials to meet demanding electrical, thermal, and mechanical specifications. One such innovation is metal-clad fiber; take, for example, silver-coated yarn. In the aerospace industry, it’s compelling to weave these lightweight fibers into flexible braids; wrapped around electrical cables, these braids prevent electromagnetic interference.

Given the high-tensile strength—these fibers can be far stronger than steel or Kevlar—flexibility, and electrical conductivity, we realized these fibers could be used to make wearable electronics and, specifically, radiofrequency (RF) coils for MRI. Thus, while aerospace applications value the fibers’ light weight and flexibility, for MRI applications we appreciated the fibers’ suitability for precise sewing into nonconductive, wearable fabrics.

AXIS: What are the stretchable, wearable coils made of?

Rispoli: We utilize the silver-coated thread as the electrical conductor for the RF coil. Our initial prototypes were fabricated by sewing the conductive thread into stretchable athletic fabrics, such as spandex. We programmed a specific stitch pattern into a professional embroidery machine; the pattern geometry facilitates stretching the RF coil without compromising the performance and reliability of the underlying electrical circuit.

AXIS: Is this specifically for use in MRI or other imaging modalities, too?

Rispoli: At present, we have adapted this technology for MRI only. Notably, the challenges associated with adapting the fabrication technique to MRI surpass those of other wearable electronic applications. That’s because MRI circuitry operates in the radiofrequency band—at tens to hundreds of megahertz—as opposed to simpler, lower-frequency circuits that aren’t as affected by the conductor path or nearby environment.

AXIS: What does the patient experience look like? How is it different from the experience a patient typically has in the MRI gantry?

Rispoli: Usually when someone gets an MRI, a receive array RF coil is positioned near the anatomy being imaged. These array coils are typically rigid and of a fixed size. Of course, these RF coils are not one-size-fits-all, and extra space between the body and the circuitry actually reduces the image quality or lengthens the required scan time. Thus, our initial designs focused on improving the patient experience for two types of scans: breast and joint MRI.

Breast MRI, while tremendously valuable given its superior sensitivity and capacity to probe dynamic physiological processes, can be uncomfortable for the prone-lying patient. Breast RF coils typically include two openings to accommodate the pendant breasts, with built-in circuitry around those openings. Often, the coil shape is mismatched for the woman’s unique anatomy. We envision our technology to be wearable and integrated into clothing as comfortable as a sports bra, improving the patient experience as well as enhancing the imaging given the closer proximity of the RF coil to the breasts.

When imaging a musculoskeletal joint, such as an elbow, knee, or hip, MRI typically necessitates the patient remain in a specific pose. This can be uncomfortable. Our stretchable RF coil technology may be wrapped or worn around joints instead, and the patient can bend their joints to a comfortable or radiologist-recommended degree of flexion.

AXIS: How would the captured images be fed into a PACS where a radiologist could interpret them?

Rispoli: Images acquired with these coils can be fed into a PACS system or similar software solution just as they can be from any other RF coil. However, we’ve shown that the closer proximity of our coils to the anatomy of interest produces images of superior quality, or they can be employed to hasten the required scan time.

AXIS: When do you expect to have this technology ready for use in healthcare? What steps do you anticipate in that journey?

Rispoli: Currently, these coils are being used for research purposes, for MRI at both 3T and 7T. Also, in step with fabricating and testing prototypes, we’ve been running and analyzing computer simulations of the coils and their interplay with the RF electromagnetic fields inherent in MRI. For these simulations, we model the RF coil on a variety of patient body sizes and shapes. These simulations and accompanying validation measurements lay the groundwork for demonstrating safe use of our stretchable RF coils and will facilitate their ultimate translation into the clinical environment.

AXIS: What vendors are you working with to test the technology?

Rispoli: Testing of these coils has been performed at the Purdue MRI Facility, where we fortuitously have access to clinical scanners from both GE Healthcare and Siemens Healthineers. Already, one major healthcare partner has expressed interest in adopting our technology, and we’re extending the technology to high-channel-count RF array coils, so, with 16 and 32 receive channels.

Aine Cryts is a contributing writer for AXIS Imaging News.