Single-phase CT angiography: collateral grade is independent of scan weighting

Collateral grading may vary on single-phase CTA (sCTA) depending on whether the CTA is arterial (A), arteriovenous (AV), or venous (V) weighted. We studied the impact of sCTA weighting on collateral grading using the Tan, MAAS, and Menon methods, and their ability to predict infarct and clinical outcome hypothesizing that AV-weighted sCTA should better predict these outcomes.

Multicenter retrospective analysis of 212 patients undergoing baseline CTP/sCTA. sCTA weighting was determined by comparing ICA to torcula AV ratios with those from concomitant CTP time-density curves at peak arterial or venous contrast attenuation. A generalized linear mixed model investigated the predictive value for infarct volume or 90-day mRS of the three collateral scores stratified by sCTA weighting and adjusting for age, sex, clot burden score (CBS), and NIHSS. Bayesian information criterion (BIC) differences were calculated between the null and fitted models.

Mean age, baseline median NIHSS, ASPECTS, and onset to treatment time were 69.89 ± 14.45, 13 (6-18), 10 (8-10), and 128 (66-181) minutes. sCTA scans were AV-weighted in 137/212 (65%) and A-weighted in 73 (34%). No association was demonstrated between sCTA weighting, hospital site, and sCTA technique. All collateral scores were related to infarct volume irrespective of sCTA weighting, with greatest fit with the regional leptomeningeal score (BIC 18.29, p = 0.0001). No association was shown between sCTA weighting, collateral grade, and clinical outcome.

sCTA weighting did not significantly impact collateral grade using three common collateral scores or their ability to predict final infarct.