Brain Atrophy and White Matter Changes Grading Agreement on NCCT and MRI in Ischemic Stroke

Brain frailty measures like atrophy and white matter changes (WMC) are becoming increasingly relevant in stroke outcome prediction but are conventionally thought to be best seen on MRI compared to CT. We assessed agreement between baseline CT vs follow-up MRI ratings for brain atrophy and WMC; and compared their discriminative ability for 90-day functional outcomes in acute ischemic stroke.

In this post-hoc, observational analysis of baseline CT and follow-up MRI data from the Alteplase compared to Tenecteplase (AcT) randomised-controlled trial, experts assessed brain atrophy, periventricular and deep WMC using established visual-rating scales. Binary agreement (none-mild vs. moderate-severe) and agreement across the full scores between atrophy and WMC measures on CT and MRI were calculated using Gwet's agreement coefficient (AC1). Logistic regression estimated discrimination for 90-day modified Rankin Scale (mRS) 0-1. Agreement of AUCs for CT and MRI models were compared using DeLong's test.

Among 1577 AcT participants, 491(31.1%) had interpretable CT and MRI. Binary agreement was substantial for periventricular (AC1 = 0.70) and total WMC (AC1 = 0.68) scores, Koedam scale (AC1 = 0.76) and frontal atrophy (AC1 = 0.80). Almost perfect agreement (AC1:0.81-0.97) was found for deep WMC (AC1 = 0.85), and the other atrophy scores (AC1 = 0.81-0.97). There was no significant difference between NCCT or MRI in discriminating 90-day mRS 0-1 for any measures.

CT ratings of brain atrophy and WMC by experts have substantial to almost-perfect agreement compared to MRI. Both achieve similar discrimination of 90-day functional outcomes. This implies the reasonable use of CT scans in evaluating brain frailty measures in clinical practice and stroke trials.