MRI FOR THE EVALUATION OF REGIONAL MYOCARDIAL PERFUSION IN AN EXPERIMENTAL ANIMAL-MODEL

Myocardial perfusion was assessed in nine pigs using ultrafast gradien t-echo MRI (.5 T, 15-mT/m gradients) at different levels of myocardial blood flow (range,.005-1.84 ml/min/g), generated either by adenosine infusion or by a mechanical occluder, and measured independently using radiolabeled microspheres, Sixty-four consecutive, EGG-triggered, dia stolic, short axis images of the left ventricle were obtained during i ntravenous bolus injections (n = 30) of .05 mmol/kg of gadopentetate d imeglumine, Relative changes in peak intensity, time to peak intensity , washin slope, correlation coefficient, and cross-correlation coeffic ient were computed from the time-intensity curves obtained from four r egions of interest, namely septal, anterior, lateral, and inferior wal ls, The values from the inferior wall acted as reference for evaluatin g relative changes in the other three regions, The cross-correlation c oefficient (P < .001, rho = .60) and the peak intensity (P <,001, r =. 72) showed the best correlation with myocardial blood now, The washin slope showed a weak positive trend (P <.05), but the low value of r (r =.28) indicated that the use of this parameter to predict now was inv alid; the correlation coefficient and time to peak intensity were not correlated (P = ns), In conclusion, this study shows that it is possib le to evaluate relative myocardial perfusion after the first pass of a an intravenously injected bolus of gadopentetate dimeglumine, using d ynamic MRI on a conventional medium held MRI system. The cross-correla tion coefficient and the peak intensity resulted in more efficient par ameters to evaluate relative inhomogeneity of regional myocardial perf usion.