Measurement of the distribution volume of gadopentetate dimeglumine at echo-planar MR imaging to quantify myocardial infarction: comparison with 99mTc-DTPA autoradiography in rats.
OBJECTIVE
To measure the fractional distribution volume of gadopentetate dimeglumine in normal and reperfused infarcted myocardium at magnetic resonance (MR) imaging by using the fractional distribution volume of technetium 99m-diethylenetriaminepentaacetic acid (DTPA) as an independent reference.


METHODS
Rats were subjected to 1 hour of coronary artery occlusion and 1 hour of reperfusion before inversion-recovery echo-planar imaging or autoradiography. Regional change in relaxation rate (delta R1) ratios for myocardium over blood were compared with radioactivity ratios for myocardium over blood after the injection of 99mTc-DTPA.


RESULTS
Both delta R1 and radioactivity ratios demonstrated equilibrium distribution and hence represent partition coefficients (lambda). The fractional distribution volumes were greater in infarcted myocardium (0.90 +/- 0.05 for gadopentetate dimeglumine and 0.89 +/- 0.04 for 99mTc-DTPA) than in normal myocardium (0.23 +/- 0.02 for gadopentetate dimeglumine and 0.16 +/- 0.01 for 99mTc-DTPA). Area at risk at autoradiography was not significantly different from that at histomorphometry. The infarction size defined by using triphenyltetrazolium chloride was 13% +/- 4 smaller than that defined by using autoradiography.


CONCLUSIONS
The fractional distribution volumes of gadopentetate dimeglumine and 99mTc-DTPA are similar and indicate extracellular distribution in normal myocardium and intracellular as well as extracellular distribution in reperfused infarction. Because the failure of cells to exclude these agents is indicative of necrosis, contrast medium-enhanced MR imaging may be useful to quantify myocardial infarction.
Arheden
H
H
Department of Radiology, University of California San Francisco Medical Center 94143-0628, USA.
Saeed
M
M
Higgins
C B
CB
Gao
D W
DW
Bremerich
J
J
Wyttenbach
R
R
Dae
M W
MW
Wendland
M F
MF
D000818:Animals; D001345:Autoradiography; D003287:Contrast Media; D017352:Echo-Planar Imaging; D005260:Female; D019786:Gadolinium DTPA; D006321:Heart / Q000000981:diagnostic imaging; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000000981:diagnostic imaging; D009206:Myocardium / Q000473:pathology; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D051381:Rats; D017207:Rats, Sprague-Dawley; D016284:Technetium Tc 99m Pentetate
D003287:Contrast Media; D019275:Radiopharmaceuticals; D019786:Gadolinium DTPA; D016284:Technetium Tc 99m Pentetate