Utilization of Synthetic Hematocrit Derived from Cardiac MRI for Estimating Extracellular Volume

Objective: For a correct estimation of extracellular volume, patients’ blood samples must be taken at least within 24 hours after cardiac magnetic resonance imaging, which may cause problems in immediate or retrospective evaluation. The aim of this study is to demonstrate the applicability of synthetic hematocrit for the calculation of extracellular volume. Materials and Methods: Cardiac magnetic resonance images including T1 mapping were retrospectively reviewed. Medical records of each patient were also collected and patients who had blood samples including hematocrit values within 24 hours of cardiac magnetic resonance imaging were included in the study. Simple linear regression along with intraclass correlation coefficient were used to calculate the coefficient of determination and agreement between the two measurements of hematocrit and extracellular volume values. The compatibility of the synthetic extracellular volume with the native extracellular volume was analysed using “Kappa Analysis”. Results: Synthetic and native hematocrit values showed significant correlation (p<0.001). Synthetic hematocrit had a high intraclass correlation coefficient (0.833). Kappa analysis for each region (Apex κ=0.88, Mid κ=0.75, Basal κ=0.87) showed significant interobserver reliability (p<0.001). Conclusion: Synthetic hematocrit formulas for each vendor may help improve synthetic extracellular volume values without contrast administration.