Dual effects of gadodiamide injection in depiction of the region of myocardial ischemia

The high safety index of the nonionic magnetic resonance (MR) contrast agent gadodiamide injection permits a wide dose range without induction of hemodynamic effects. The wide dose range might confer a diagnostic advantage by providing both T1 enhancing and magnetic susceptibility effects for demarcating pathologic regions. The dual utility of this contrast agent for T1 and T2 enhancement in creating differential contrast between normal and acutely ischemic myocardium was explored. MR imaging was initiated 20-40 minutes after occlusion of the left coronary artery in two groups of rats: Group 1 (n = 8) received 0.3 mmol/kg gadodiamide injection before and after acquisition of T1-weighted images; group 2 (n = 10) received 0.5 mmol/kg before and after acquisition of T2-weighted images. Postcontrast T1-weighted images showed clear delineation of the ischemic region as a relatively low-signal-intensity area for 15 minutes. On postcontrast T2-weighted images, the ischemic region appeared as a relatively high-signal-intensity area for 60 minutes. These effects were obtained with doses of gadodiamide injection that have safety indexes greater than those of gadopentetate dimeglumine.