Quantification of myocardial iron and fat-an experimental study with photon-counting detector CT

To determine the feasibility and accuracy of photon-counting detector (PCD)-CT for iron and fat quantification in the myocardium.

Cylindrical tubes were filled with porcine myocardium and iron citrate with iron concentrations of 0-20 mg Fe g-1. 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 3-material decomposition was used to separate iron and fat from myocardium.

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 1.2 HU (mg Fe g-1)-1 with an intercept of 35.8 HU (R2 = 0.964). In the fat probes, the slope was similar at 1.1 HU (mg Fe g-1)-1, while the regression line shifted downwards by 6.1 HU with an intercept of 29.6 HU (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.

Experimental evidence indicates the feasibility and accuracy of PCD-CT for iron and fat quantification in the myocardium. Iron-specific 3-material decomposition eliminates the confounding effect of fat on myocardial iron quantification.

This study highlights the value of dual-energy CT with 3-material decomposition for quantifying iron and fat in the myocardium. Thus, CT could serve as alternative for the current reference standard MRI.