Vascular-Augmented Two-Compartment Fitting Improves Model Performance for Intermittent Myocardial T1 Mapping

ObjectivesConventional gadolinium-enhanced cardiac magnetic resonance imaging (MRI) typically evaluates myocardial tissues at a single post-contrast time point. In contrast, dynamic T1 mapping enables the estimation of contrast agent concentrations and subsequent pharmacokinetic modeling. This study compared a normal composite two-compartment model incorporating myocardial vascular components with the conventional Brix model. Materials and MethodsThis retrospective study included 107 participants who underwent dynamic T1 mapping at 2, 5, 9, and 15 min after contrast administration. Exclusion criteria included contraindications to MR imaging, acute coronary syndrome, pregnancy, an estimated glomerular filtration rate < 30 mL/min/1.73 m2, claustrophobia, and known allergy to gadolinium-based contrast medium. Contrast agent concentrations derived from MOLLI-based T1 maps were fitted using the Brix and composite pharmacokinetic models. Model performance was assessed using the residual sum of squares (RSS), Akaike information criterion (AIC), and Bayesian information criterion (BIC). The myocardial blood fraction estimated by the composite model was compared with the extracellular volume (ECV). ResultsThe composite model exhibited significantly lower RSS, AIC, and BIC values than the Brix model (all p < 0.001). Absolute parameter estimation errors were reduced across all time points. The estimated myocardial blood fraction averaged 35.0% and demonstrated a positive correlation with the ECV (r = 0.61, p < 0.001). ConclusionsIn myocardial pharmacokinetic analysis using dynamic T1 maps, the composite model achieved superior fitting performance compared with the Brix model. Explicit incorporation of vascular kinetics improves the longitudinal characterization of contrast behavior and enhances quantitative assessment of myocardial tissue properties.