麻豆传媒

LOS ANGELES -- An investigational low-power MRI scanner appeared safe and feasible for use at the bedside in a standard neuroscience ICU, researchers reported.

The required no shielding, no special power supply, no changes to the equipment used in the patient's room, and no precautions for ferrous metal, Bradley Cahn, BS, of Yale University School of Medicine in New Haven, Connecticut, and colleagues reported here at the .

Among 96 stroke patients scanned non-acutely (minimum 9 hours post-onset, mean 87 hours), there were no "significant" adverse events. Overall, 87% of participants completed the full exam: six participants experienced claustrophobia, and five didn't fit head and shoulders comfortably into the 30-cm opening.

Acquisition times were about 7.5 minutes for T2-weighted scans, 9.5 for FLAIR, 9.8 for diffusion-weighted imaging, and just shy of 29 minutes for a full exam.

Portable CT machines are already in clinical use for stroke, notably in mobile stroke units, noted Ralph Sacco, MD, chairman of neurology at the University of Miami and past president of the American Heart Association.

"If we could get MRI as quickly as CT scanning, some of us would prefer MRI over CT," he said in an interview.

MRI is a more sensitive indicator of brain injury and can pick up ischemia much earlier in the process when CT might still give a false negative, he noted.

The bulky machines needed to generate high-powered 3- and even 7-T MRI, risk posed by stray metal, as well as the wait and acquisition times have been hurdles, though, Sacco added.

"We have this incredibly safe technology, MRI, and we've put it in depths of the hospital's basement where you have to travel with the patient to get to it," said Cahn. "We've flipped that and brought the magnet into the patient's room."

There are plenty of other possible useful applications, though, said Cahn. Availability in the emergency room and ambulance "would be huge."

However, 28 minutes -- while fast for MRI -- might be just too long to consider overthrowing CT as the standard for urgent diagnosis in most circumstances, said ISC session moderator Justin Fraser, MD, of the University of Kentucky in Lexington. But it could be particularly useful for posterior circulation strokes, to determine futility of thrombectomy, he suggested.

The device still needs to be tested in the acute setting, though, Cahn noted.

"I think what they intended to prove, they proved that it was both feasible and safe to do in this limited, single-center population," commented Peter Panagos, MD, of Washington University School of Medicine in St. Louis, and American Heart Association/American Stroke Association Stroke Council Chair.

The study included both intubated and non-intubated adults in the neuroscience ICU who needed imaging as standard of care. Those with contraindications to 1.5-T MRI were excluded.

In theory, the device should be compatible with MR-compatible pacemakers and similar devices, but that hasn't been tested yet either, noted Cahn. "We just don't know how the low field strength interacts with devices like that. For example, some devices [that] are safe at 3 T may not be at 7 T and vice versa."

Nor were any scans done with contrast administration. Those studies will come, Cahn said, and the device continues to be iteratively improved.

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