Assessment of extracellular volume fraction using dual-energy CT in doxorubicin-induced dilated cardiomyopathy in a rabbit model : comparison with contrast-enhanced magnetic resonance imaging and histology

Abstract

Purpose: To assess the feasibility of extracellular volume (ECV) fraction using dual-energy computed tomography (CT) and to compare it with magnetic resonance imaging (MRI) T1 mapping and histologic findings.

Materials and methods: A dilated cardiomyopathy rabbit (DCR) model was made by injecting doxorubicin into the rabbits (adult male New Zealand white rabbits, 3-4 kg) at doses of 1.0 mg/kg twice a week. Every rabbit underwent both dual-energy CT and magnetic resonance imaging (MRI) within two hours with pre-/post-contrast T1 mapping using modified Look-Locker inversion recovery (MOLLI) sequence, late gadolinium enhancement (LGE), and cine MR on a clinical 3-T system. The rabbits underwent CT and MR examination before drug administration (control group) and DCR model at various post-modeling intervals (6 weeks, 12 weeks or 16 weeks after DCR modeling). CT ECV was quantitatively assessed by measuring Hounsfield units (HUs) in the septum in a cardiac short-axis view on iodine maps. MR ECV was assessed in the same area with CT. The left ventricle ejection fraction (LVEF) was obtained from the cine MR images using Simpson''s method.

Results: Fifteen rabbits were scanned prior to modeling, and then four controls were sacrificed for histology. The remaining eleven underwent DCR modeling and were scanned at various post-modeling intervals (Group I; 6-week modeling, n = 11: group II; 12-week modeling, n = 8: and group III; 16-week modeling, n = 5). The mean CT ECV values (%) of group I-III were significantly higher than control group (Control vs. group I vs. group II vs. group III; 28.5 (range, 25.9-31.3) vs. 35.3 (range, 30.2-40.1) vs. 41.9 (range, 35.6-44.1), vs. 42.1 (range, 39.2-46.4), p < 0.001) and there was a good correlation between CT ECV and MR ECV (r = 0.888, p < 0.001) and between CT ECV and degree of fibrosis (r = 0.811 p < 0.001)

Conclusion: ECV using dual-energy CT shows good correlation with MRI and histology. Noninvasive measurement of ECV in animals with doxorubicin-induced diffuse myocardial fibrosis is feasible with dual-energy CT without misregistration errors.