ABSTRACT NUMBER: ESOC2026A188 SPECTRAL PHOTON-COUNTING DETECTOR CT FOR COMPREHENSIVE EVALUATION OF CAROTID PLAQUE AND STENOSIS

Abstract Background and aims Conventional CT is limited in differentiating soft-plaque components due to overlapping attenuation values and is frequently affected by calcification-related blooming artifacts that obscure vessel lumen and may overestimate stenosis. Photon-counting detector CT (PCD-CT) can provide enhanced spatial resolution or spectral discrimination compared with conventional energy-integrating CT, potentially improving carotid plaque characterization and mitigating artifact-related limitations. This study systematically evaluated image quality and plaque and stenosis assessment across spectral PCD-CT reconstructions. Methods We retrospectively included patients who underwent PCD-CT for carotid stenosis assessment. Four monoenergetic (ME; 40-55-70-85 keV), pure lumen (PL), and virtual non-contrast (VNC) reconstructions were analyzed. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), edge sharpness, plaque area, degree of NASCET stenosis, and attenuation of plaque components (intraplaque hemorrhage, lipid-rich necrotic core, fibrotic tissue, calcification) were compared using repeated-measures ANOVA with Bonferroni correction. Results Our study included 27 patients (16 men, age: 74.5 ± 9.1 years) with 50 plaques. CNR and SNR decreased with increasing ME levels (P < 0.001), while noise increased. PL yielded CNR and sharpness comparable to ME55, whereas VNC exhibited near-zero lumen signal. Stenosis remained consistent across ME reconstructions (44-45%, P = 1.00), but significantly reduced for PL (38%, P < 0.001). Lower-energy reconstructions (ME40/ME55) improved separation of attenuation values between lumen and the various plaque components. Conclusions Low-energy PCD-CT reconstructions enhance CNR and sharpness without affecting plaque and stenosis measurements. The PL algorithm may improve calcified plaque assessment, where conventional reconstructions may overestimate stenosis. PCD-CT shows promise for advanced plaque composition evaluation but further validation against MRI and histology is warranted. Conflict of interest Juul Bierens: nothing to disclose, Jelske Kuijpers: nothing to disclose, Luca Saba: nothing to disclose, Luc J.M. Smits: nothing to disclose, Robert J. van Oostenbrugge: nothing to disclose, Thomas Flohr: nothing to disclose, M. Eline Kooi: nothing to disclose, Alida A. Postma: nothing to disclose. Figure 1 - belongs to Methods Figure 2 - belongs to Results