The Feasibility of Low Contrast Dose Dual-energy CT for Quantifying Myocardial Focal Scar via Extracellular Volume Fraction

Objective To explore the quantitative efficacy of low-contrast-agent-dose dual-energy CT (DECT) myocardial extracellular volume (ECV) for myocardial focal scar (MFS). Methods 33 patients with confirmed old myocardial infarction (OMI) were prospectively enrolled. All underwent DECT late iodine enhancement (LIE), cardiac magnetic resonance(CMR) late gadolinium enhancement (LGE), native and enhanced T1 mapping. DECT-LIE-ECV and CMR-ECV were measured in 1–16 myocardial segments of the left ventricle. Additionally, with reference to the CMR-LGE images, DECT-LIE-ECV and CMR-ECV of the MFS and the remote myocardium at a same slice were measured. Quantitative performance was assessed via Spearman correlation, Bland-Altman analysis, ROC curves, and DeLong's tests. Results A total of 438 myocardial segments from 28 patients were analyzed (including 101 MFS-positive, 337 MFS-negative). (2) MFS-positive segments showed higher ECV than MFS-negative (CMR: 41% vs. 29%; DECT: 33% vs. 25%). DECT-LIE-ECV correlated weakly with CMR-ECV (r = 0.21, p < 0.001) but had moderate agreement (mean bias: 0.8%). Diagnostic accuracy was lower for DECT (AUC: 0.711) than CMR (AUC: 0.892; p < 0.001). (3) Lesion-level: MFS regions had higher ECV than remote myocardium (CMR: 57% vs. 27%; DECT: 48% vs. 25%). DECT-LIE-ECV correlated strongly with CMR-ECV (r = 0.76, p < 0.001) and showed moderate agreement (mean bias: 0.8%). Both methods had near-perfect diagnostic accuracy (DECT AUC: 0.989; CMR AUC: 0.985; p = 0.720). Conclusion Low-contrast DECT-LIE-ECV accurately quantifies MFS when targeting scar regions directly, offering a promising supplementary tool for myocardial scar quantification, especially for patients with contraindications to CMR.