Arterial brain calcium (ABC) volume - A novel radiological marker of atherosclerotic risk and future stroke risk on non-contrast CT.

BACKGROUND AND PURPOSE: Coronary calcium is a well-recognized marker of atherosclerotic risk. While intracranial carotid artery calcification has received some attention, calcific disease in other intracranial arteries is not well studied. In this pilot study, we sought to examine the whether the total volume of calcium in the intracranial arteries is associated with established markers of atherosclerosis and stroke risk.

METHODS AND METHODS: We examined a subset of 360 consecutive cases in a population-level cohort of 7,745 patients representing all patients diagnosed with ischemic stroke/TIA in an entire Canadian province (Alberta) from 1-April-2016 to 31-March-2017. Trained readers manually segmented visible calcifications in all intracranial arteries on non-contrast CT using ITKSnap. Volumetric data for all segmentations were combined to obtain the total Arterial Brain Calcium (ABC) volume. We related this volume to the total burden of vascular risk factors, number of vessels with intracranial atherosclerotic disease, atherosclerosis burden in different territories using ordinal logistic regressions adjusted for age and sex, and to the 5-year risk of recurrent events using Poisson regressions.

RESULTS: Among 360 cases (median age: 68 years, IQR:56-80), ABC volume (median:5.40 mL, 95 % CI:3.05-7.85 mL) increased with age (per-year increase: 66.5 mm3, 95 % CI:37.5-95.5 mm3) and was lower in females (4.22 mL, IQR:0.25-6.37 v/s 6.60 mL, IQR:0.35-8.33, p = 0.0004). ABC volume was independently associated with the burden of intracranial arterial (age/ sex-adjusted common odds-ratio [acOR] per mL increase:1.14, 95 %CI:1.04-1.26) and combined intracranial/carotid/ aortic/ coronary atherosclerosis (acOR:1.18, 95 %CI:1.10-1.27), and vascular risk factors (acOR:1.07, 95 %CI:1.01-1.13). Those with higher ABC volume had a higher risk of recurrent events (IRR:3.20, 95 % CI:1.24-8.25).

CONCLUSIONS: ABC volume derived from routine non contrast CT scan may be utilised as a novel imaging marker of atherosclerotic burden and merits further validation as a predictive tool in recurrent ischemic stroke/ TIA.