Regional myocardial blood volume and flow: First‐pass MR imaging with polylysine‐Gd‐DTPA

The authors investigated the utility of an intra‐vascular magnetic resonance (MR) contrast agent, poly‐L‐lysine‐gadolinium diethylenetriaminepentaacetic acid (DTPA), for differentiating acutely ischemic from normally perfused myocardium with first‐pass MR imaging. Hypoperfused regions, identified with microspheres, on the first‐pass images displayed significantly decreased signal intensities compared with normally perfused myocardium (P < 0.0007). Estimates of regional myocardial blood content, obtained by measuring the ratio of areas under the signal intensity‐versus‐time curves in tissue regions and the left ventricular chamber, 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 tissue 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‐pathway, axially distributed model. Flow estimates, obtained by automated parameter optimization, averaged 1.2 mL/min/g ±0.5 (n =29), compared 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 combination of T1‐weighted first‐pass imaging, intravascular relaxation agents, and a spatially distributed perfusion model to obtain absolute regional myocardial blood flow and volume.