Portable MRI at Bedside Feasible for Detecting Stroke

LOS ANGELES — Neuroimaging of people with suspected stroke in an intensive care unit can help guide diagnosis and management, but often requires transporting patients to a CT or MRI scanner, which itself can be challenging.

Researchers decided to flip this scenario and evaluate stroke patients by bringing MRI technology to the point-of-care setting.

"We report here the first use of a portable, low-field MRI system to image stroke patients at the bedside. This early work suggests this approach is both safe and feasible in a complex clinical care environment," said lead author Bradley Cahn, BS, a researcher in the Department of Neurology at Yale School of Medicine in New Haven, Connecticut.

Cahn presented the findings here during at the 2020 International Stroke Conference (ISC).

Low-Field MRI Moving Toward Practicality

Neuroimaging is used extensively to diagnose, triage and, manage people who experience a stroke. Noncontrast CT and high-field MRI are the most common modalities. "MRI, in particular, allows for accurate and reliable detection of ischemia and hemorrhage," Cahn said.

Cost, availability, the need for shielded rooms, and trained technicians can be limitations to high-field MRI, he added.

"Recent improvements in hardware, software, and image reconstruction have made it possible to obtain clinically useful imaging at the point of care using a low-field magnet."

Using a point-of-care 1.5 Tesla MRI scanner, Cahn, senior author Kevin Sheth, MD, and colleagues assessed 96 adults in the neuroscience ICU. All participants presented with a clinical diagnosis of stroke or other brain injury between June 2018 and January 2020.

Stroke subtypes included acute ischemic stroke, subarachnoid hemorrhage and intracerebral hemorrhage. The average age was 63 years, 51% were women, and the mean NIH Stroke Scale score was 8 (range, 0 to 37).

Feasibility and Safety Outcomes

A majority, 87% of patients, successfully completed the entire exam at the bedside. The group that did not complete the imaging included 6 patients who experienced claustrophobia and 5 patients unable to fit comfortably in the scanner's 30 cm (11.8 in) opening. A full exam took an average of 29 minutes.

"The scanning did not interfere with any NICU [neurological intensive care unit] equipment in any clinically significant way," Cahn said.

The device can be plugged into a standard wall outlet and exams were performed successfully on both intubated and non-intubated patients.

No significant adverse events occurred during the study.

"It's important to note that hardware and software are continuously improving, yielding higher quality images," Cahn said.

The investigators plan to expand their research. "We recognize that this approach must be evaluated in the hyperacute setting and across a wide range of stroke characteristics," he added.

Ongoing projects for Cahn and colleagues include expanding enrollment to the emergency department, quantifying the image quality and signal intensities, and evaluating the scanner's sensitivity to specific stroke presentations.

Useful in Select Patients?

"There are some very specific diagnoses and management scenarios where this would be helpful," session moderator Justin F. Fraser, MD, director of cerebrovascular surgery in the Department of Neurological Surgery at University of Kentucky HealthCare in Lexington, told Medscape Medical News.

A patient on extracorporeal membrane oxygenation (ECMO) therapy, for example, could not be easily moved to an MRI scanner. A person with venous sinus thrombosis who is intubated or sedated would also present a challenge in this regard, Fraser said.

"We don't want to move them, but we want to know if they are experiencing more strokes from their venous sinus thrombosis," he added. CT can also give you that, but there are limits, he added.

Portable, bedside MRI "could be a very useful tool," he added, "but more than likely, it will be used selectively."

"Overall, I think what they intended to prove, they proved — that it was both feasible and safe to do in this limited, single-center population," Peter D. Panagos, MD, professor of emergency medicine, Washington University School of Medicine in St. Louis, Missouri, said in a video commentary accompanying the abstract.

"It's a fascinating abstract," added Panagos, who is also AHA/ASA Stroke Council Chair.

The study was funded by a collaborative science award from the American Heart Association and Hyperfine Research. Cahn received a research grant from Hyperfine Research. Fraser and Panagos have disclosed no relevant financial relationships.

International Stroke Conference (ISC) 2020: Abstract 57.
Presented February 19, 2020.

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