Quantitative assessment of bioprosthetic heart valve calcification using photon-counting CT

Background Valve replacement is the standard treatment for severe valvular heart disease, with bioprosthetic heart valves (BHVs) increasingly favored due to lower thrombogenicity and improved hemodynamics. Despite advances in biomaterials, BHVs remain susceptible to structural valve degeneration (SVD), largely driven by calcification. While coronary calcium scoring is standardized, there is no validated quantitative approach for assessing native or bioprosthetic valvular calcification. Conventional CT provides limited material characterization. Photon-counting computed tomography (PCCT), with improved spatial resolution, reduced artifacts, and spectral material discrimination capabilities, offers a promising platform for quantitative assessment of BHV degeneration. Purpose To evaluate the feasibility of PCCT and its spectral imaging techniques for quantitative characterization of BHV calcification and structural valve degeneration. Methods 11 calcified BHV explants were obtained from our Biobank. Valves were positioned in a plastic phantom and suspended in 9 mg/mL iodine solution. Imaging was performed using the NAEOTOM Alpha PCCT system (Siemens Healthineers) with a 140 kV Ultra High-Resolution Quantum Plus protocol (reconstruction: iMAR 0.40 mm, Qr40, QIR 3). DICOM datasets were processed in 3D Slicer to segment regions containing calcium. Calcium density for each segmented voxel was calculated using an adapted virtual unenhanced workflow on Siemens Syngo Via VB60. Low and high energy images were generated from spectral datasets. Maximum intensity projection (MIP) maps were created to visualize the spatial distribution and concentration of calcification. Results Among the 11 explanted valves, 8 were from the aortic position and 3 from the mitral position. Mean age of patients at explantation was 70.82 ± 5.06 years. Mean implantation duration was 9.91 ± 4.21 years (maximum 17 years). Segmented calcium volume ranged widely from 4.27 mm³ to 889.82 mm³, reflecting heterogeneous degeneration patterns. The mean low-to-high energy ratio was 1.74 ± 0.24. Calculated calcium densities ranged from 360.10 to 763.87 mg/mL (mean 590.05 ± 131.47 mg/mL). Maximum intensity projection maps demonstrated heterogeneous spatial distribution of calcification within valve leaflets (Figure 1). Conclusion PCCT enables high-resolution, quantitative assessment of bioprosthetic valve calcification, providing both volumetric and density-based characterization beyond conventional CT capabilities. PCCT-based calcium mapping may represent a novel imaging biomarker for early detection and monitoring of BHV degeneration. Furthermore, quantitative characterization of leaflet calcification could support procedural planning and risk stratification in transcatheter valve-in-valve interventions. These findings highlight the potential of PCCT to bridge the current gap between structural imaging and mechanistic understanding of bioprosthetic valve failure.