Ultra-high-resolution Photon-Counting CT for Leaflet-Specific Evaluation of Fibrosis and Calcification in Aortic Stenosis

Objectives

Ultra-high-resolution photon-counting detector (PCD)-CT may enable leaflet-specific analysis of aortic valve fibrosis and calcification, providing insights into early aortic stenosis (AS) disease progression. This study aimed to investigate how PCD-CT leaflet-specific calcific and fibrotic volumes influence cardiovascular magnetic resonance (CMR) leaflet mobility.

Materials and methods

Participants with moderate aortic AS prospectively underwent both PCD-CT (n=80) and CMR (n=58). Using PCD-CT, calcific and fibrotic volumes were segmented for right (RCC), left (LCC), and non-coronary cusps (NCC) and indexed to the aortic annulus area (ICV and IFV). CMR-derived leaflet mobility index (LMI) was assessed. Two raters compared image quality using a Likert-scale (1=poor to 5=excellent) and distinguishability of individual leaflets in PCD-CT with EID-CT (n=82).

Results

PCD-CT analysis showed that calcification was higher in males (e.g., ICV _RCC : 15±16 vs. 4±7 µL/cm ² ;p<0.001) while fibrosis was higher in females (e.g., IFV _LCC ; 47±18 vs. 34±15 µL/cm ² ;p=0.004) across all leaflets. Fibrocalcific ratio was higher in LCC (53±276) compared to RCC (19±48;p<0.001) and NCC (13.5±34;p<0.001). LMI of RCC was higher in females compared to men (0.66±0.21 vs. 0.38±0.33;p=0.008). LMI _LCC and LMI _NCC showed no sex differences.

LMI _RCC negatively correlated with ICV _RCC (ρ=-0.64[-0.77, −0.46];p<0.001) and LMI _NCC with ICV _NCC (ρ=-0.69[-0.80, −0.53];p<0.001), whereas LMI _LCC negatively correlated with IFV _LCC (ρ=-0.35[-0.56,-0.10];p=0.007), particularly in females (ρ=-0.70[-0.89, −0.31];p = 0.003). PCD-CT yielded higher image quality (5[IQR4–5] vs. 3[3–4];p<0.001) and leaflet distinguishability (79/80[99%] vs. 42/82[51%];p<0.001) than EID-CT.

Conclusions

Ultra-high-resolution PCD-CT allows for leaflet-specific quantification of indexed fibrotic and calcific volume. These volumes demonstrate sex- and leaflet-specific differences that may distinctly contribute to AS pathophysiology.

Key Points

Detailed leaflet-level characterization of fibrotic and calcific remodeling in aortic stenosis remains limited with energy integrating CT.

Photon-counting CT enabled reliable leaflet-specific quantification of fibrosis and calcification, identified sex-related tissue distribution patterns, and demonstrated associations between calcification and impaired leaflet mobility.

Leaflet-specific photon-counting CT assessment may enhance our understanding of aortic stenosis progression and support more individualized imaging evaluation through improved differentiation of fibrotic and calcific valvular remodeling.

Clinical Trials Registration

NCT05851209