Abstract： Objective:To explore the value of quantitative parameters of dynamic CT myocardial perfusion imaging (CT-MPI) in evaluating coronary microcirculation dysfunction (CMD) in a porcine model.Methods:Ten Chinese miniature pig age of 5 to 8 months were randomly selected in this experimental study. After anesthesia, a micro guide wire was introduced via a percutaneous direct puncture through superficial femoral artery. Then 1 ml of microsphere mixture, which contained 0.5×10 5/0.5 ml of microsphere, was slowly injected into the distal of anterior descending artery to establish a CMD animal model. Resting and stress CT-MPI were performed 60 min before and 10 min after CMD. The quantitative parameters of dynamic CT-MPI including myocardial blood flow (MBF) and myocardial blood volume (MBV) were measured. Using the changes of MBF and MBV before and after CMD as self-references, a paired-sample t test was used to compare the differences of MBF and MBV of resting and stress CT-MPI before and after CMD. The animals were sacrificed for myocardial histopathological examination after the imaging examination. Results:Of the 10 experimental animals, two pigs died, and CMD model was successfully established in the other 8 pigs. The MBF and MBV of CMD myocardial segments in resting CT-MPI were (98.6±20.9) ml·100 ml -1·min -1 and (9.0±2.8) ml/100 ml, respectively. The MBF and MBV of CMD myocardial segments in stress CT-MPI were (87.6±14.6) ml·100 ml -1·min -1 and (8.0±1.8) ml/100 ml, respectively. Both of the MBF and MBV of CMD myocardial segments in resting CT-MPI were significantly reduced, compared with those of the normal myocardial segments ( P<0.001). HE staining showed myocardial infarcts interspersed with normal myocardial foci at low magnification. Pathological alterations, including myocardial cytoplasm cohesion, eosinophil level variations, stripe disappearance, nuclear relocation, and cardiomyocyte interstitial edema, were displayed at high-magnification by microscopy. Conclusions:In this experimental study of CMD animal models, MBF and MBV of dynamic CT-MPI were significantly decreased in CMD myocardial segments compared with those before CMD. The changes of MBF or/and MBV can be used as dynamic CT-MPI quantitative parameters for evaluation of CMD.