Myocardial Extracellular Volume Fraction with Dual-Energy Equilibrium Contrast-enhanced Cardiac CT in Nonischemic Cardiomyopathy: A Prospective Comparison with Cardiac MR Imaging

Purpose: To evaluate the feasibility of equilibrium contrast material-enhanced dual-energy cardiac computed tomography (CT) to determine extracellular volume fraction (ECV) in nonischemic cardiomyopathy (CMP) compared with magnetic resonance (MR) imaging. Materials and Methods: This study was approved by the institutional review board; informed consent was obtained. Seven healthy subjects and 23 patients (six with hypertrophic CMP, nine with dilated CMP, four with amyloidosis, and four with sarcoidosis) (mean age 6 standard deviation, 57.33 years +/- 14.82; 19 male participants [63.3%]) were prospectively enrolled. Twelve minutes after contrast material injection (1.8 mL/kg at 3 mL/sec), dualenergy cardiac CT was performed. ECV was measured by two observers independently. Hematocrit levels were compared between healthy subjects and patients with the Mann-Whitney U test. In per-subject analysis, interobserver agreement for CT was assessed with the intraclass correlation coefficient (ICC), and intertest agreement between MR imaging and CT was assessed with Bland-Altman analysis. In per-segment analysis, Student t tests in the linear mixed model were used to compare ECV on CT images between healthy subjects and patients. Results: Hematocrit level was 43.44% +/- 1.80 for healthy subjects and 41.23% +/- 5.61 for patients with MR imaging (P = .16) and 43.50% +/- 1.92 for healthy subjects and 41.35% +/- 5.92 for patients with CT (P = .15). For observer 1 in per-subject analysis, ECV was 34.18% +/- 8.98 for MR imaging and 34.48% +/- 8.97 for CT. For observer 2, myocardial ECV was 34.42% +/- 9.03 for MR imaging and 33.98% +/- 9.05 for CT. Interobserver agreement for ECV at CT was excellent (ICC = 0.987). BlandAltman analysis between MR imaging and CT showed a small bias (-0.06%), with 95% limits of agreement of -1.19 and 1.79. Compared with healthy subjects, patients with hypertrophic CMP, dilated CMP, amyloidosis, and sarcoidosis had significantly higher myocardial ECV at dual-energy equilibrium contrast-enhanced cardiac CT (all P < .01) in per-segment analysis. Conclusion: Myocardial ECV with dual-energy equilibrium contrast-enhanced CT showed good agreement with MR imaging findings, suggesting the potential of myocardial tissue characterization with CT. (C) RSNA, 2016