In vivo MRI measurement of blood oxygen saturation in children with congenital heart disease

Objective: The purpose of this prospective study was to measure in vivo blood oxygen saturation (%O₂) by MRI in children with congenital heart disease (CHD) using population-based values for T₂O (T₂ signal decay of fully oxygenated blood) and K (a parameter representing the deoxyhemoglobin effect) and compare the %O₂ with direct cardiac catheterization measurements. Background: MRI can determine %O₂ using in vivo measurement of signal decay (T₂) and an in vitro calibration curve relating T₂ and %O₂, based on the equation: 1/T₂=1/T₂O+K(1−%O₂/100)². Recent studies have correlated the T₂/%O₂ in children with CHD with the adult calibration statistics. Methods: A total of ten children (five male, five female) with single ventricle CHD (median age 4.8 months, range 2 months to 4.4 years) undergoing cardiac catheterization were included in the study. The blood T₂ measurements for each patient were performed in a 1.5 T GE CV scanner. The %O₂ was then calculated based on the equation using values of T₂O determined from individual hematocrits, and a population average value of K derived for children. The %O₂ values were compared with direct %O₂ measurements from cardiac catheterization. Results: The %O₂ values by MRI were strongly correlated with direct cardiac catheterization measurements (R=0.825; P<0.001). Conclusion: The study indicates that the noninvasive measurement of %O₂ by MRI can accurately measure oxygen saturation in children with complex CHD.