Detsky J S, Stainsby J A, Vijayaraghavan R, Graham J J, Dick A J, Wright G A
Department of Imaging Research, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
Magn Reson Med. 2007 Aug;58(2):365-72. doi: 10.1002/mrm.21291.
Delayed-enhancement magnetic resonance imaging (DE-MRI) can be used to visualize myocardial infarction (MI). DE-MRI is conventionally acquired with an inversion-recovery gradient-echo (IR-GRE) pulse sequence that yields a single bright-blood image. IR-GRE imaging requires an accurate estimate of the inversion time (TI) to null the signal from the myocardium, and a separate cine acquisition is required to visualize myocardial wall motion. Simulations were performed to examine the effects of a steady-state free precession (SSFP) readout after an inversion pulse in the setting of DE-MRI. Using these simulations, a segmented IR-SSFP sequence was optimized for infarct visualization. This sequence yields both viability and wall motion images over the cardiac cycle in a single breath-hold. Viability images at multiple effective TIs are produced, providing a range of image contrasts. In a study of 11 patients, IR-SSFP yielded infarct sizes and left ventricular ejection fractions (LVEFs) similar to those obtained by IR-GRE and standard SSFP, respectively. IR-SSFP images yielded improved visualization of the infarct-blood border because of the simultaneous nulling of healthy myocardium and blood. T(1) (*) recovery curves were extracted from IR-SSFP images and showed excellent qualitative agreement with theoretical simulations.
延迟增强磁共振成像（DE-MRI）可用于观察心肌梗死（MI）。传统上，DE-MRI是通过反转恢复梯度回波（IR-GRE）脉冲序列采集的，该序列可生成单幅亮血图像。IR-GRE成像需要准确估计反转时间（TI）以消除心肌信号，并且需要单独进行电影采集以观察心肌壁运动。进行了模拟，以研究在DE-MRI设置中反转脉冲后稳态自由进动（SSFP）读出的效果。利用这些模拟，优化了用于梗死灶可视化的分段IR-SSFP序列。该序列在一次屏气过程中可在心动周期内生成存活心肌和心肌壁运动图像。可生成多个有效TI下的存活心肌图像，提供一系列图像对比度。在一项对11名患者的研究中，IR-SSFP得出的梗死灶大小和左心室射血分数（LVEF）分别与IR-GRE和标准SSFP获得的结果相似。由于健康心肌和血液同时被消除信号，IR-SSFP图像改善了梗死灶与血液边界的可视化。从IR-SSFP图像中提取了T(1)*恢复曲线，结果显示与理论模拟具有良好的定性一致性。
