Diagnostic Value of Carotid Ring Sign in Predicting Internal Carotid True Occlusion

BACKGROUND AND PURPOSETo differentiate between pseudo-occlusion (PO) and true occlusion (TO) of internal carotid artery (ICA) is important in thrombectomy treatment planning for acute ischemic stroke (AIS) patients. Although delayed contrast filling has been differentiated carotid PO from TO, its application has been limited by the implementations of multiphasic computed tomography angiography (mCTA). In this study, we hypothesized that carotid ring sign, which is readily acquired from single-phasic CTA, can sufficiently differentiate carotid TO from PO. METHODSTwo hundred patients with non-visualization of the proximal ICA were included. Diagnosis of PO or TO of the cervical segment of ICA was made based on digital subtraction angiography. Diagnostic performances of carotid ring sign on arterial-phasic CTA and delayed contrast filling on mCTA were evaluated and compared. RESULTSOne-hundred-twelve patients had ICA PO and 88 had TO. Carotid ring sign was more common in TO patients (70.5% vs 6.3%, p<0.001), while delayed contrast filling was more common in PO (94.9% vs 7.7%, p<0.001). The sensitivity and specificity of carotid ring sign in diagnosing carotid TO was 0.70 and 0.94 respectively, while sensitivity and specificity of delayed contrast filling was 0.95 and 0.92 in judging carotid PO. CONCLUSIONSCarotid ring sign is a potent imaging marker in diagnosing ICA TO. Carotid ring sign could be complementary to delayed contrast filling sign in differentiating TO from PO, in particular in centers with only single-phasic CTA.