| Abstract: | The purpose of this study was (1) to monitor the dynamic effects Of T1 -enhancing and magnetic SUSCCPtibility contrast material on normal canine myocardium using inversion recovery (IR)- and driven equilibrium @E)-prepared fast gradient-recalled echo (GRE) sequences and (2) to determine the relative value of T1-enhancing and magnetic eusceptibflity contrast material in detecting regions of ischemia in the same animal. Normal dogs (n = 5) and dogs with acute occlusion of the left anterior descending (LAD] coronary artery [n = 11) were studied using a 1.5-T NIR imager. ECG-gated fast IR-prepared GRE images were acquired using TI/TR/TE of 700/7.0/2.9 msec and a flip angle of 7°. Fast DE-prepared GRE images were obtained using a flip angle of 12° and a DE delay /TR/TE of 60/10.2/4.2 msec. Sequential images were acquired to monitor transit of 0.06 mmol/kg gadodiamide injection and 0.2 and 0.4 mmol/kg sprodiamide injection. On slice-nonselective IR fast GRE images. gadodiamide caused signiflcant enhancement of the normal myocardium and the left ventricular (LV) chamber blood. In dogs with LAD occlusion, the ischemic region was defined as an area of low signal intensity (SI). On DE-prepared GRE sequences, administration of sprodiamide resulted in a substantial decrease in signal from normal myocardium and LV chamber blood in normal dogs. In animals subjected to LAD occlusion, this contrast medium produced a transient decrease in SI from normal myocardium [P <.06) and no signiflcant change in SI from ischemic myocardium. IR- and DE-prepared taet GRE imaging can be used to monitor the transit of Tl-enhancing and magnetic susceptibility contrast material in the heart. respectively. Cardiac image quality was much better when slice-nonselective IR-prepared fast GRE sequences were used rather than DE-prepared fast GRE. |
