Spectral Photon-Counting Detector CT for Comprehensive Evaluation of Carotid Plaque and Stenosis

Background – Conventional energy-integrating detector (EID) CT is limited in differentiating soft-plaque components due to overlapping attenuation values and is frequently affected by calcification-related blooming artifacts that obscure the vessel lumen and may overestimate stenosis. Photon-counting detector CT (PCD-CT) can provide enhanced spatial resolution and spectral discrimination compared with conventional EID-CT, potentially improving carotid plaque characterization and mitigating artifact-related limitations. This study systematically evaluated image quality, plaque component attenuation, and stenosis visualization across spectral PCD-CT reconstructions. Methods – We retrospectively included patients who underwent PCD-CT for carotid stenosis assessment. Four monoenergetic (ME 40, 55, 70, and 85 keV), PureLumen (PL), and virtual noncontrast (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 y) with 50 plaques. CNR, SNR, and noise decreased with increasing ME levels (P<0.001). PL yielded CNR and sharpness comparable to ME55, whereas VNC exhibited a near-zero lumen signal. Stenosis remained consistent across ME reconstructions (44% to 45%, P=1.00), but significantly reduced for PL (38%, P<0.001). Lower-energy reconstructions (ME40/ME55) improved the separation of attenuation values between the lumen and the various plaque components. Conclusion – Low-energy PCD-CT reconstructions enhance CNR and sharpness while maintaining consistent plaque and stenosis measurements. The PL algorithm may improve the assessment of calcified plaques, where conventional reconstructions may overestimate stenosis. PCD-CT shows promise for advanced plaque composition evaluation, but further validation against MRI and histology is warranted.