Sugimura K, Kawamitsu H, Yoshikawa K, Yuasa K, Kasai T, Okizuka H
Department of Radiology, Shimane Medical University, Izumo, Japan.
Clin Radiol. 1994 Dec;49(12):871-3. doi: 10.1016/s0009-9260(05)82878-8.
ECG-gated spin-echo imaging can reduce vascular artefacts compared with spin-echo scans without gating. However, this method produces poor T1-weighted images because the repetition time (TR) is limited by the heart rate. We investigated the value of low flip angle spin-echo imaging for increasing T1-dependent contrast when using ECG gating. Using computer simulation, the predicted contrast increased with decreasing the flip angle, and the effect was almost saturated at a flip angle of around 40 degrees. With the application of this flip angle, the identical image contrast as a T1-weighted image (TR = 400 ms) can be obtained within the heart rate range of 65 to 75 beats/min. For clinical evaluation, the tissue contrast index values ((signal intensity in the lesion-signal intensity in the muscle)2 x 100/signal intensity in the muscle) obtained by conventional spin-echo and low flip angle spin-echo imaging were compared in 17 patients. The contrast index of low flip angle spin-echo images (74.0 +/- 52.0) was significantly higher than that of conventional spin-echo images (40.9 +/- 35.9). Thus, ECG-gated low flip angle spin-echo imaging provided better T1-dependent contrast than conventional ECG-gated spin-echo imaging. This method may be especially useful for Gd-DTPA-enhanced magnetic resonance imaging.
与非门控自旋回波扫描相比，心电图门控自旋回波成像可减少血管伪影。然而，这种方法产生的T1加权图像质量较差，因为重复时间（TR）受心率限制。我们研究了在使用心电图门控时，低翻转角自旋回波成像对于增加T1依赖性对比度的价值。通过计算机模拟，预测的对比度随着翻转角的减小而增加，并且在大约40度的翻转角时效果几乎达到饱和。应用这个翻转角，在心率范围为65至75次/分钟时，可以获得与T1加权图像（TR = 400毫秒）相同的图像对比度。为了进行临床评估，对17例患者通过传统自旋回波和低翻转角自旋回波成像获得的组织对比度指数值（（病变中的信号强度 - 肌肉中的信号强度）²×100/肌肉中的信号强度）进行了比较。低翻转角自旋回波图像的对比度指数（74.0±52.0）显著高于传统自旋回波图像的对比度指数（40.9±35.9）。因此，心电图门控低翻转角自旋回波成像比传统心电图门控自旋回波成像提供了更好的T1依赖性对比度。这种方法可能对钆喷酸葡胺增强磁共振成像特别有用。
