Abstract TP249: From Thick to Hyperfine: Evaluating Portable MRI Against CT for Subdural Hematoma Thickness

Background: Accurate assessment of subdural hematoma (SDH) thickness is critical for clinical decision-making. While non-contrast computed tomography (CT) remains the gold standard, Hyperfine portable low-field MRI offers key advantages by eliminating radiation exposure and can be performed at the bedside in both inpatient and outpatient settings. Methods: At our community based, university medical center, we retrospectively analyzed 15 patients with acute, subacute, and chronic convexity SDHs who underwent both non-contrast CT and Hyperfine MRI within a 3 day period. Maximum SDH thickness was measured in both the axial and coronal planes. Agreement between modalities was assessed using Bland–Altman analysis, and paired t-tests were performed to evaluate systematic differences. Results: A Bland–Altman analysis demonstrated good overall agreement between Hyperfine MRI and CT in measuring convexity SDH thickness. In the axial plane, Hyperfine measurements were on average 0.35 mm greater than CT (bias = +0.35 mm), with 95% limits of agreement ranging from –3.20 to +3.90 mm. In the coronal plane, Hyperfine measurements were on average 0.71 mm less than CT (bias = –0.71 mm), with wider 95% limits of agreement (–6.61 to +5.20 mm). Paired t-tests showed no statistically significant difference between modalities in either the axial (p = 0.47) or coronal (p = 0.38) views. Discussion: These findings indicate that portable low-field MRI provides comparable estimates of SDH thickness relative to non-contrast CT. The small mean differences suggest no systematic bias, and the lack of statistical significance reinforces that Hyperfine measurements are not meaningfully different from CT. Agreement was tighter in the axial plane, where differences generally remained within ±4 mm, whereas coronal measurements showed greater variability, extending to ±6 mm. From a clinical perspective, these differences are unlikely to alter decision-making in most cases, particularly for monitoring hematoma progression or stability. Importantly, Hyperfine MRI offers the advantages of avoiding radiation exposure and enabling bedside imaging, which may expand access to neuroimaging in settings where CT is less practical or safe.