We compared single-source cardiac CT (CCT) and cardiac MRI (CMR) measurements of right ventricular (RV) volumes and function in congenital heart disease (CHD) patients. CCT consistently measures higher RV volumes and lower ejection fraction (EF) compared to CMR, with the greatest difference between contours in the basal and mid-inferior RV segments. The findings suggest that CMR-derived pulmonary valve replacement (PVR) criteria, when applied to CCT, lead to earlier intervention. Adjusting CCT m…