MR imaging of the myocardium using nonionic contrast medium: signal-intensity changes in patients with subacute...

Gadodiamide injection (Omniscan, Sanofi Winthrop Pharmaceuticals, New York) is a new nonionic MR contrast medium that has been shown in animal studies to provide persistent differential enhancement of myocardial infarction. Because differential enhancement of normal and infarcted myocardium may be useful for the diagnosis and sizing of myocardial infarctions, we assessed the effectiveness of gadodiamide injection in enhancing signal-intensity differences between infarcted and normal myocardium on spin-echo T1-weighted images.

Signal intensity of normal and infarcted myocardium, contrast ratio, contrast-to-noise ratio, and signal-to-noise ratio were measured in 12 patients with subacute myocardial infarction (mean, 16 days after diagnosis) before and after injection of contrast medium. Precontrast T1-weighted and T2-weighted images were obtained with a 1.5-T MR imager. T1-weighted images were acquired 5, 15, and 30 min after gadodiamide injection (0.2 mmol/kg) and T1-weighted images with fat saturation were acquired 10 min after gadodiamide injection.

Gadodiamide injection significantly increased signal intensity of normal (34 +/- %) and infarcted (90 +/- %) myocardium compared with their signal intensities on precontrast T1-weighted images. The contrast ratio was significantly increased, and the augmented ratios persisted throughout the 45-min observation period. The contrast ratio on T2-weighted images was comparable to that on contrast-enhanced T1-weighted images (with or without the use of fat saturation). However, the signal-to-noise and contrast-to-noise ratios of T2-weighted images were significantly lower than those of contrast-enhanced T1-weighted images. The maximum contrast-to-noise ratio for visualizing myocardial infarction was achieved on contrast-enhanced T1-weighted images with fat saturation.

Improved and persistent contrast between infarcted and normal myocardium can be produced on MR images by injecting gadodiamide at a dose of 0.2 mmol/kg, which provides prolonged delineation of myocardial infarctions. Maximum contrast-to-noise ratios for detecting myocardial infarction can be produced by using fat-saturated T1-weighted imaging after a high dose of this nonionic contrast medium has been administered.