Conventional high resolution versus fast T-2-weighted MR imaging of the heart: assessment of reperfusion induced myocardial injury in an animal model

Cardiac image quality in terms of spatial resolution and signal contrast wa s assessed for conventional and newly developed T-2-weighted fast spin-echo imaging with high k-space segmentation. The capability in revealing region al myocardial edema and cellular damage was examined by a porcine model usi ng histopathologic correlation. Twelve porcine hearts were excised from sla ughtered animals and instantly perfused with 1000 mL cold cardioplegic solu tion. After 4 h of cold ischemia the hearts were reperfused for one hour us ing a "Langendorff" perfusion model followed by MR imaging at 1.5 Tesla. Th ree additional pig hearts served as controls and were studied by MR directl y after harvesting. Histopathological analysis of regional tissue changes w as performed macro- and microscopically. Short axis T-2-weighted (3000/45 a nd 90) high quality fast spin-echo (FSE) images were recorded without cardi ac action and signal intensity was correlated with histology. These images also served as gold standard for evaluation of newly developed faster seque nces allowing measuring times shorter than 20 s. Fast T-2-weighted imaging comprised single-slice fast spin echo (moderate echo train length of 23 ech oes, FSEm), and multi-slice single-shot half-Fourier fast spin-echo (71 ech oes, FSEHASTE) sequences, supplemented by versions with inversion recovery preparation (FSEmIR and FSEHASTEIR). Systolic function after reperfusion wa s restored in 10 porcine hearts. Tissue alterations included myocardial ede ma and contraction band necrosis which was found to be most severe in myoca rdium with maximum T2SI. Especially FSEm and FSEmIR sequences allowed diffe rentiation of all categories of tissue damage on a high level of significan ce. In contrast, single-shot FSEHASTE and FSFHASTEIR sequences did not prov ide sufficient image quality to discriminate moderate and severe myocardial damage (p > 0.05). Different degrees of myocardial injury after ischemia a nd reperfusion can be staged by MR imaging, especially using conventional h igh resolution T-2-weighted FSE sequences. The animal study indicates that fast T-2-weighted FSEm and FSEmIR sequences lead to superior image quality and diagnostic accuracy compared to FSEHASTE and FSEHASTEIR imaging. (C) 20 00 Elsevier Science Inc. All rights reserved.