Portable Bedside Low-field MRI for Assessment of Ventricular Size.

Abstract

Background and purpose: Low-field portable MRI (pMRI) has been shown to be a useful alternative neuroimaging tool in the emergency department (ED) and intensive care unit (ICU), potentially addressing challenges associated with the transport of critically ill patients. We aimed to evaluate the intermodality reliability between low-field pMRI and conventional neuroimaging (CN) for assessment of ventricular size and hydrocephalus.

Materials and methods: This retrospective study included all patients who underwent point-of-care 64mT pMRI at a single tertiary hospital from March 30, 2022 to January 4, 2024, and had a follow-up CN, either CT or MRI, performed within 24 hours of the pMRI scan. Two raters independently evaluated pMRI images for presence of hydrocephalus while blinded to CN. Bifrontal diameter, maximum skull and Evans index were recorded. Interrater and intermodality agreement between pMRI and CN were evaluated by using the intraclass coefficient (ICC) and Cohen's kappa.

Results: Fifty-six patients (mean age of 53.5 (± 14.6) years, 61% male) were included in this study. Hydrocephalus was identified in 12 (21%) on pMRI and 13 (23%) on CN. Interrater agreement on pMRI was almost perfect for bifrontal diameter (ICC 0.94, 95% CI 0.89-0.97), Evans index (ICC 0.92, 95%CI 0.86-0.95) and substantial for determination of hydrocephalus (κ = 0.72), all p <0.01. Intermodality agreement between pMRI and CN was also near perfect for averaged measurements of bifrontal diameter (ICC 0.94, 95% CI 0.88-0.97), Evans index (ICC 0.95, 95%CI 0.92-0.97) and determination of hydrocephalus (κ = 0.95), all p<0.01. Using CN as reference standard, pMRI had sensitivity and specificity of 92% (95% CI 0.85-0.99) and 100% (95% CI 1.0-1.0), respectively on qualitative visual assessment, and 80% (95% CI 0.70-0.90) and 98% (95% CI 0.94-1.0), respectively on quantitative assessment using an Evans index cut off of 0.3.

Conclusions: Low-field pMRI demonstrated excellent interrater agreement and strong concordance with CN in assessing ventricular size, highlighting its potential as an effective point-of-care tool for neuro-critical care applications.

Abbreviations: pMRI= portable MRI; CN = conventional neuroimaging; ED= emergency department; ICU= intensive care unit; ICC= intraclass coefficient; pCT= portable CT; TCS = Transcranial Sonography.