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

BACKGROUND AND PURPOSE To 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. METHODS Two 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. RESULTS One-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. CONCLUSIONS Carotid 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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by National Health Commission Capacity Building and Continuing Education Center, grant number GWJJ2021100203, Natural Science Foundation of Fujian Province (Grant No. 2022J01123138). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The ethics committee of Zhangzhou Affiliated Hospital of Fuiian Medical UniversityZhangzhou Municipal Hospital Ethics Committee I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The data that support the findings of this study are available on request from the corresponding author.