MRI quantitative myocardial perfusion with compartmental analysis: A rest and stress study

K₁ [first-order transfer constant from arterial plasma to myocardium for Gd-DTPA) and Vd (distribution volume of Gd-DTPA in myocardium) were measured in vivo in a canine model (n = 5) using MRI-derived myocardial perfusion curves and a compartmental model. Perfusion curves were obtained after a bolus injection of Gd-DTPA (0.04 mM/kg) with an inversion-prepared fast gradient echo sequence. Myocardium and blood signal intensity were converted to a concentration of Gd-DTPA, according to a model appropriate for short (< 1 s) interimage intervals characteristic of cardiac-triggered acquisitions. Before dipyridamole-induced stress, K₁ and Vd, obtained from the fit of the MRI-derived perfusion curves, were 6.2± 1.4 (mHz) and 17.5 ± 4.2%, respectively. After dipyridamole infusion, a K₁ increase of a factor of 2.82 ± 0.72 was measured (P = 0.003). No change was observed in Vd (P = 0.98). These results suggest that the K₁ increase after dipyridamole reflects a flow-related effect that can be useful to quantify the MRI- derived perfusion curves.