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

Aortic valve Agatston score (AVAS) at 70 keV decreased significantly with thinner CT sections.

• AVAS at 3-mm section: 2141 (95% CI: 1931, 2351)
• AVAS at 1-mm section: 1900 (95% CI: 1690, 2110)
• AVAS at 0.4-mm section: 1791 (95% CI: 1581, 2001)
• Difference across all section thicknesses was statistically significant (P < .001)
• Study included 84 patients with median age 84 years (IQR: 80–88 years), 58 female

Aortic valve calcium volume (AVCV) decreased significantly with thinner CT sections.

• AVCV at 3-mm section: 1806 mm³ (95% CI: 1640, 1972)
• AVCV at 1-mm section: 1496 mm³ (95% CI: 1330, 1661)
• AVCV at 0.4-mm section: 1373 mm³ (95% CI: 1207, 1538)
• Difference across all section thicknesses was statistically significant (P < .001)

Aortic valve calcium mass (AVCM) differed minimally across section thicknesses.

• AVCM at 3-mm section: 518 mg (95% CI: 452, 585)
• AVCM at 1-mm section: 525 mg (95% CI: 459, 592)
• AVCM at 0.4-mm section: 527 mg (95% CI: 461, 594)
• Differences were statistically significant overall (P < .001) except for the comparison between 1-mm and 0.4-mm sections (P = .24)
• AVCM was relatively stable compared to the larger changes seen in AVAS and AVCV

Use of thinner sections resulted in reclassification of aortic stenosis severity in 8–9% of patients compared to 3-mm sections.

• Seven of 84 patients (8.3%) were reclassified from CT-severe to CT-nonsevere at 1-mm versus 3-mm sections
• Eight of 84 patients (9.5%) were reclassified from CT-severe to CT-nonsevere at 0.4-mm versus 3-mm sections
• Reclassification difference was statistically significant (P < .001)
• Sex-specific AVAS thresholds were used: ≥2000 for male patients and ≥1300 for female patients

Regression-based equivalent AVAS thresholds for aortic stenosis severity classification were lower at thinner section thicknesses.

• At 1-mm sections, equivalent thresholds were 1770 for male patients and 1154 for female patients
• At 0.4-mm sections, equivalent thresholds were 1675 for male patients and 1087 for female patients
• These values are lower than the standard 3-mm thresholds of ≥2000 (male) and ≥1300 (female)
• Thresholds were derived from regression analyses comparing thin-section scores to the standard 3-mm reference