A schematic diagram describing the measurement of pulmonary arterial compliance by MRI. Total pulmonary arterial compliance is the sum of arterial volume compliances in the main, right and left pulmonary arteries (CMPA, CRPA and CLPA, respectively). These, in turn, are computed from area compliances (CAMPA, CARPA and CALPA), respectively, multiplied by vessels’ lengths as reported in the literature.