CTA-based imaging parameters for differentiating tandem from isolated internal carotid artery occlusion: development of a multivariable prediction model.

OBJECTIVE: Differentiating tandem from isolated internal carotid artery (ICA) occlusion is important for guiding treatment to achieve the best outcomes, as tandem lesions are associated with more complex strategies and potentially worse outcomes. Although computed tomography angiography (CTA) is widely used, diagnostic challenges such as pseudo-occlusions-false-positive imaging findings-limit reliability. This study evaluates whether quantitative imaging parameters can support the distinction. METHODS: This retrospective, single-center study included 71 patients diagnosed with ICA occlusion between 2020 and 2024. 35 patients in the tandem group and 36 in the isolated ICA occlusion group were included. The demographic information (age, sex, occlusion etiology, and comorbidity) and CTA-based imaging parameters were collected. Predictors were selected among candidates using univariate, penalized regression, and pairwise Pearson correlation analyses. The primary three-predictor model was estimated using Firth penalized logistic regression and evaluated using internal validation and calibration. RESULTS: Demographic data were comparable among study groups, except age. Following the multistep predictor-selection process, the mean density of the occluded ICA pre-occlusion (Mean_Occl_ICA_pre), the mean densities of the thrombus permeability ratio (Thrm_Perm_Ratio_Mean), and the gradient ratio of the occluded ICA post-occlusion (GR_Occl_ICA_post) were included in the final model. The model showed a bootstrap optimism-corrected AUC of 0.713. CONCLUSION: The combination of CTA-derived attenuation parameters showed modest discrimination between tandem and isolated ICA occlusion. These parameters may provide complementary diagnostic information, but validation in larger independent cohorts is required.