Effect of CT Section Thickness on Aortic Valve Calcium Scoring via Photon-counting Detector CT

Purpose To evaluate the effect of section thickness on aortic valve calcification quantification via photon-counting detector (PCD) CT. Materials and Methods This retrospective study included patients who underwent electrocardiography-gated PCD CT from March 2023 to October 2024. The aortic valve Agatston score (AVAS), aortic valve calcium volume (AVCV), and aortic valve calcium mass (AVCM) were measured at 3-mm, 1-mm, and 0.4-mm sections. Linear mixed model and regression analyses were performed. Sex-specific AVAS thresholds were used for aortic stenosis (AS) severity classification (≥2000 for male patients, ≥1300 for female patients). Results Eighty-four patients (median age: 84 years [IQR: 80-88 years], 58 female) were included. AVAS at 70 keV decreased with thinner sections: 3-mm section, 2141 (95% CI: 1931, 2351); 1-mm section, 1900 (95% CI: 1690, 2110), and 0.4-mm section, 1791 (95% CI: 1581, 2001) (<i>P</i> < .001). AVCV decreased similarly: 1806 mm³ (95% CI: 1640, 1972), 1496 mm³ (95% CI: 1330, 1661), and 1373 mm³ (95% CI: 1207, 1538) (<i>P</i> < .001). AVCM differed minimally: 518 mg (95% CI: 452, 585), 525 mg (95% CI: 459, 592), and 527 mg (95% CI: 461, 594) (<i>P</i> < .001 except for 1 mm vs 0.4 mm, <i>P</i> = .24). Compared with 3-mm sections, seven of 84 (8.3%) and eight of 84 (9.5%) patients were reclassified from CT-severe to CT-nonsevere with 1- and 0.4-mm sections, respectively (<i>P</i> < .001). Regression-based equivalent thresholds were 1770 (male patients) and 1154 (female patients) at 1 mm and 1675 (male patients) and 1087 (female patients) at 0.4 mm. Conclusion Thin-section PCD CT decreased AVAS and AVCV, resulting in AS severity reclassification in 8%-9% of patients. <b>Keywords:</b> Applications-CT, CT-Photon Counting, Cardiac, Aortic Valve, Calcifications/Calculi <i>Supplemental material is available for this article.</i> © RSNA, 2026.