We sought to determine performance of portable MRI (pMRI) on floor level Acute Ischemic Stroke (AIS) patients.

Portable MRI has practical advantages over high-field MRI (hMRI) in evaluating AIS. Prior studies only evaluated pMRI in the ICU setting, not on floor level patients. 

We retrospectively reviewed floor status AIS patients who had pMRI obtained during their hospitalization. We reviewed pMRI for its ability to visualize confirmed infarcts on hMRI (gold standard). Incomplete or technically limited scans were excluded. Our institutional pMRI (Hyperfine) is a 0.064 Tesla machine, with sequences including diffusion-weighted imaging (DWI), Apparent diffusion coefficient, and fluid-attenuated inversion recovery (scan time 24 minutes).  Infarct size was measured based upon maximum longitudinal axis on DWI.

Among 12 AIS patients, the mean age was 58.5 years (range, 25 to 88), and 7 (58.3%) were female. Mean time from hMRI to pMRI was 46.2 hours (range, -0.9 to 126.9 hrs).  Mean Time from Last Known Normal (LKN) to pMRI was 3.6 days (range, 0.87 to 7.8 days). In 9/12 (75%) patients, pMRI demonstrated acute infarcts (7/12 scans demonstrated all infarcts seen on hMRI, 2/12 scans identified some but not all infarcts). Three (25%) pMRI DWI were negative. 

On 12 hMRI scans, 15 infarct lesions were demonstrated.  Infarct distribution on hMRI showed: cortical (9), deep (1), medullary (1), thalamus (3), and cerebellar (1).  Among the 15 infarcts demonstrated on hMRI, 10/15 (67%) were also visible on pMRI. The mean size of infarcts that were not visible on pMRI was 7.7 mm, compared to visible infarcts which had a mean size of 21.7mm (p = 0.0436).  The smallest infarct that was visible on pMRI was 7.7mm.

pMRIs performed reasonably well on floor-level AIS patients and was able to detect a majority of acute infarcts seen on hMRI, with limitations on smaller sized infarcts.