Usage of the T1 effect of an iron oxide contrast agent in an animal model to quantify myocardial blood flow by MRI
Received 28 July 2006; received in revised form 30 November 2006; accepted 1 December 2006.
Abstract
Background
To present a new method for fully quantitative analysis of myocardial blood flow (MBF) using magnetic resonance imaging. The first pass of an intravascular iron oxide contrast medium can be used to quantify myocardial perfusion. The technique was validated in an animal model using colored microspheres.
Materials and methods
In six pigs, a tracking catheter was positioned in the left anterior descending artery (LAD). Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was performed on a 1.5-T scanner using a hybrid gradient-echo/echoplanar imaging (GRE-EPI) sequence. Regional myocardial blood flow (rMBF) was altered by either inducing vasodilatation with adenosine or creating coronary artery obstruction. The T1 effect of a superparamagnetic iron oxide-based contrast medium (Resovist®) administered at a dose of 8μmol/kg was used. Upslope, time-to-peak and peak intensity were calculated from the signal intensity–time curves and absolute rMBF using the Kety–Schmidt equation; results were compared to those obtained using colored microspheres.
Results
The mean rMBF calculated by MRI was 1.49 (±6.91, quartile width) ml/min/g versus 3.21 (±1.61) ml/min/g measured by means of microspheres under resting conditions. rMBF increased to a mean of 6.21 (±2.83) ml/min/g versus 4.22 (±1.70) ml/min/g under adenosine and was reduced to zero flow in total occlusion. Linear regression showed the best correlation for upslope (R=0.714), time-to-peak (R=0.626) and the Kety–Schmidt equation (R=0.584).
Conclusions
The T1 effect of an iron oxide-based contrast medium allows determination of rMBF when using the Kety–Schmidt equation. The results are similar to those obtained with the standard of reference, colored micropheres, but not better than the results of the semiquantitative approach.
ABSTRACT