Discrepancies in Vessel Diameter Measurements Between CTA and DSA in MCA M1 Occlusions: An Interobserver Study

Accurate vessel measurement is essential in endovascular thrombectomy (EVT) for acute ischemic stroke. Discrepancies between computed tomography angiography (CTA) and digital subtraction angiography (DSA) may impact procedural planning and device selection. This study compares vessel diameter measurements from CTA and DSA in patients with middle cerebral artery (MCA) M1 occlusions.

In this single-center retrospective study, 90 consecutive patients who underwent EVT for MCA M1 occlusions between February 2020 and March 2024 were included. Vessel diameters were independently measured by 3 neuroradiologists using CTA and DSA (pre- and post-intervention). Statistical analysis included Wilcoxon signed-rank tests, intraclass correlation coefficient (ICC), and Bland-Altman analysis.

CTA consistently overestimated vessel diameter compared to DSA. The mean M1 diameter was 2.29 ± 0.27 mm on CTA and 2.16 ± 0.30 mm on pre-EVT DSA (P < .001), with a median difference of 0.4 mm (IQR: 0.2-0.6 mm). In 70% of cases, CTA values exceeded DSA. Bland-Altman analysis confirmed a mean difference of +0.13 mm (limits of agreement: -0.25 to +0.51 mm). No significant change was observed between pre- and post-EVT DSA measurements (P = .103). Clot-side M1 segments were significantly smaller than contralateral measurements on CTA (P = .003). Inter-rater agreement was good (ICC = .785).

CTA overestimates MCA M1 diameter relative to DSA. While the discrepancy is modest, it may influence device selection in borderline cases. Awareness of this variability is important, and further research is warranted to explore its clinical implications.