CMR Imaging of Edema in Myocardial Infarction Using Cine Balanced Steady-State Free Precession

Abstract

The aim of this study was to investigate the capabilities of balanced steady-state free precession (bSSFP) cardiac magnetic resonance imaging as a novel cine imaging approach for characterizing myocardial edema in animals and patients after reperfused myocardial infarction. Current cardiac magnetic resonance methods require 2 separate scans for assessment of myocardial edema and cardiac function. Mini-pigs (n = 13) with experimentally induced reperfused myocardial infarction and patients with reperfused ST-segment elevation myocardial infarction (n = 26) underwent cardiac magnetic resonance scans on days 2 to 4 post-reperfusion. Cine bSSFP, T2-weighted short TI inversion recovery (T2-STIR), and late gadolinium enhancement were performed at 1.5-T. Cine bSSFP and T2-STIR images were acquired with a body coil to mitigate surface coil bias. Signal, contrast, and the area of edema were compared. Additional patients (n = 10) were analyzed for the effect of microvascular obstruction on bSSFP. A receiver-operator characteristic analysis was performed to assess the accuracy of edema detection. An area of hyperintense bSSFP signal consistent with edema was observed in the infarction zone (contrast-to-noise ratio: 37 ± 13) in all animals and correlated well with the area of late gadolinium enhancement (R = 0.83, p < 0.01). In all patients, T2-STIR and bSSFP images showed regional hyperintensity in the infarction zone. Normalized contrast-to-noise ratios were not different between T2-STIR and bSSFP. On a slice basis, the volumes of hyperintensity on T2-STIR and bSSFP images correlated well (R = 0.86, p < 0.001), and their means were not different. When compared with T2-STIR, bSSFP was positive for edema in 25 of 26 patients (96% sensitivity) and was negative in all controls (100% specificity). All patients with microvascular obstruction showed a significant reduction of signal in the subendocardial infarction zone compared with infarcted epicardial tissue without microvascular obstruction (p < 0.05). Myocardial edema from ST-segment elevation myocardial infarction can be detected using cine bSSFP imaging with image contrast similar to T2-STIR. This new imaging approach allows evaluation of cardiac function and edema simultaneously, thereby reducing patient scan time and increasing efficiency. Further work is necessary to optimize edema contrast in bSSFP images.