Photon-Counting Detector CT Improves Visualization of the Normal Carotid Body Compared with Energy-Integrating Detector CT

BACKGROUND AND PURPOSE: The carotid bodies are small chemoreceptor organs at the carotid bifurcation. Their depiction on conventional CT angiography is inconsistent, with reported detection rates on energy-integrating detector CT (EID-CT) of 62% to 91%. This study evaluates whether photon-counting detector CT (PCD-CT) improves carotid body visualization and describes their normal imaging appearance. MATERIALS AND METHODS: This retrospective study included 37 patients who underwent both PCD-CT and EID-CT head and neck angiography, yielding 74 carotid bifurcations. Two neuroradiologists, reading in consensus, recorded whether each carotid body was definitively identifiable on each modality and rated relative image quality on a 5-point comparative Likert scale. Morphologic measurements were obtained from PCD-CT. Likert scores were analyzed with a linear mixed-effects model with a random intercept for patient; identification was compared with the McNemar test. RESULTS: Reader preference strongly favored PCD-CT (median Likert score, 5.0 [IQR, 4.0-5.0]; mixed-effects mean, 4.6; 95% CI, 4.4-4.8; P < .001). Carotid bodies were identified in all 74 bifurcations (100%) on PCD-CT versus 58 of 74 (78.4%) on EID-CT (P < .001); at least one was missed on EID-CT in 12 of 37 patients (32%). Carotid bodies were ellipsoid in 71 of 74 (95.9%), with mean anteroposterior, transverse, and superoinferior dimensions of 2.0 ± 0.7, 2.1 ± 0.7, and 2.9 ± 1.1 mm, and a median volume of 5.9 mm³ (IQR, 3.8-8.5). CONCLUSIONS: PCD-CT reliably visualizes normal carotid bodies that are frequently missed on conventional EID-CT. Familiarity with their normative appearance may reduce mischaracterization as early paraganglioma and provides a foundation for volumetric research into the carotid body's role in systemic disease.