REGIONAL MYOCARDIAL BLOOD-VOLUME AND FLOW - FIRST-PASS MR-IMAGING WITH POLYLYSINE-GD-DTPA

The authors investigated the utility of an intravascular magnetic reso nance [MR] contrast agent, poly-L-lysine-gadolinium diethylenetriamine pentaacetic acid (DTPA), for differentiating acutely ischemic from nor mally perfused myocardium with first-pass MR imaging. Hypoperfused reg ions, identified with microspheres, on the first-pass images displayed significantly decreased signal intensities compared with normally per fused myocardium (P < .0007). Estimates of regional myocardial blood c ontent, obtained by measuring the ratio of areas under the signal inte nsity-versus-time curves in tissue regions and the left ventricular ch amber, averaged 0.12 mL/g +/- 0.04 (n = 35), compared with a value of 0.11 mL/g +/- 0.05 measured with radiolabeled albumin in the same tiss ue regions. To obtain MR estimates of regional myocardial blood flow, in situ calibration curves were used to transform first-pass intensity -time curves into content-time curves for analysis with a multiple-pat hway, axially distributed model. Flow estimates, obtained by automated parameter optimization, averaged 1.2 ml/min/g +/- 0.5 (n = 29), compa red with 1.3 ml/min/g +/- 0.3 obtained with tracer microspheres in the same tissue specimens at the same time. The results represent a combi nation of T1-weighted first-pass imaging, intravascular relaxation age nts, and a spatially distributed perfusion model to obtain absolute re gional myocardial blood flow and volume.