Quantification of Myocardial Iron and Fat — An Experimental Study with Photon-Counting Detector CT

Objectives: To determine the feasibility and accuracy of photon-counting detector (PCD)-CT for iron and fat quantification in the myocardium. Materials and Methods: Cylindrical tubes were filled with porcine myocardium and iron-citrate with iron concentrations of 0-20mg Fe/g. Dilution series were prepared with myocardium and iron (no-fat probes) and with 5%-fat (fat probes). The tubes were positioned in a chest phantom and were scanned with a calcium-scoring protocol on a PCD-CT. A re-parameterized three-material decomposition was used to separate iron and fat from myocardium. Results: On virtual monoenergetic images, attenuation increased linearly with iron concentrations in both fat and no-fat probes. In no-fat probes, linear regression yielded a slope of 1.2HU/(mgFe/g) with an intercept of 35.8HU (R2=0.964). In the fat probes, the slope was similar at 1.1HU/(mgFe/g), while the regression line shifted downwards by 6.1HU with an intercept of 29.6HU (R2=0.985). Iron maps separated fat from iron with calculated median fat-fractions of 4.85 in the fat and 0.90 in the no-fat probes. In iron images, attenuation increased linearly with increasing iron concentrations, with similar slopes between fat and no-fat probes and negligible differences in the intercept. Conclusion: Experimental evidence indicates the feasibility and accuracy of PCD-CT for iron and fat quantification in the myocardium. Iron-specific three-material decomposition eliminates the confounding effect of fat on myocardial iron quantification. Advances in Knowledge This study highlights the value of dual-energy CT with three-material decomposition for quantifying iron and fat in the myocardium. Thus, CT could serve as alternative for the current reference standard MRI.