Usage of the T1 effect of an iron oxide contrast agent in an animal model to quantify myocardial blood flow by MRI.
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.


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 T(1) effect of a superparamagnetic iron oxide-based contrast medium (Resovist) administered at a dose of 8 micromol/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 T(1) 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.
Lüdemann
Lutz
L
Department of Radiology and Nuclear Medicine, Charité-Universitätmedizin Berlin, Campus Virchow-Klinikum, Germany. lutz.luedemann@charite.de
Schmitt
Boris
B
Podrabsky
Petr
P
Schnackenburg
Bernhard
B
Böck
Johannes
J
Gutberlet
Matthias
M
D000241:Adenosine / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D021721:Balloon Occlusion / Q000009:adverse effects; D001783:Blood Flow Velocity / Q000187:drug effects; D003287:Contrast Media; D003326:Coronary Circulation / Q000187:drug effects; D023921:Coronary Stenosis / Q000209:etiology / Q000503:physiopathology; D004195:Disease Models, Animal; D005290:Ferric Compounds; D006352:Heart Ventricles / Q000187:drug effects / Q000503:physiopathology; D007089:Image Enhancement; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods; D008863:Microspheres; D009206:Myocardium / Q000473:pathology; D012107:Research Design; D013552:Swine; D013997:Time Factors; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D003287:Contrast Media; D005290:Ferric Compounds; D014665:Vasodilator Agents; C000499:ferric oxide; D000241:Adenosine