Direct comparison of an intravascular and an extracellular contrast agent for quantification of myocardial perfusion

A direct comparison of extracellular and intravascular contrast agents for the assessment of myocardial perfusion was carried out in a porcine model ( N = 5) with a flow-limiting occluder on the left anterior descending corona ry artery. Rapid imaging during the first pass of an extracellular or intra vascular contrast agent with a saturation-recovery-prepared TurboFLASH sequ ence showed comparable peak contrast-to-noise enhancements in myocardial ti ssue regions with flows averaging 1.1 +/- 0.2 at baseline to 4.8 +/- 0.6 ml /min/g during hyperemia. The coefficient of variation between the MR estima tes of blood flow with Gadomer-17 and the microsphere blood flow measuremen ts was 11 +/- 11, while the corresponding coefficient of variation for bloo d flow estimates with the extracellular CA was 23 +/- 11. Blood volume diff erences between rest and hyperemia observed with the intravascular tracer w ere significant (V-vasc(rest) = 0.078 +/- 0.013 ml/g, versus V-vasc(hyperem ia) = 0.102 +/- 0.019 ml/g; p < 0.05). The effects of water exchange were m inimized through the choice of pulse sequence parameters to provide blood v olume estimates consistent with the changes expected between rest and hyper emia. This study represents the first application of multiple indicators in first pass imaging studies for the assessment of myocardial perfusion. The use of an intravascular instead of an extracellular contrast agent allows a reduction of the degrees of freedom for modeling tissue residue curves an d results in improved accuracy of blood flow estimates.