Sieverding L, Jung W I, Klose U, Apitz J
Universitätsklinik, Abt. für pädiatrische Kardiologie, Universität Tübingen.
Z Kardiol. 1990 Nov;79(11):774-82.
Based on the phase difference method as described by Nayler et al., we developed a gradient-echo sequence, which refocuses flow-related phase shifts. With regard to the higher peak velocity and higher acceleration in infants, we reduced the echo time (TE) to 5 ms. This is effective in rephasing the flow signals even for faster heart rates. Phase shifts are further minimized by reducing the voxel size. The slice thickness down to 2 mm also improves anatomic resolution. A repetition time (TR) of 15 ms provides high temporal resolution for dynamic studies. Modification of the flow-rephasing gradient-echo sequence allows blood flow measurements in the great arteries and the calculation of blood flow volume to assess left and right ventricular stroke volume. This can also be achieved by calculating the ventricular volume from contiguous slices of the whole heart; however, it results in excessive measuring times. Compared with conventional spin-echo techniques, anatomical analysis is improved. The size of atrial septal defects (ASD) can be measured more exactly. Small atrial or ventricular septal defects (VSD), which are not detectable on spin-echo images, are demonstrated on the gradient-echo images and semi-quantitative estimation of the pressure in the right and left ventricle can be made. Pulmonary arteries and veins are clearly differentiated from bronchial structures and are traced to subsegmental levels. Without ECG-gating, contiguous slices of interesting parts of the cardiovascular system can be obtained and successfully used for secondary angiographic reconstructions.
基于纳勒等人描述的相位差法，我们开发了一种梯度回波序列，该序列可重新聚焦与血流相关的相移。考虑到婴儿较高的峰值速度和加速度，我们将回波时间（TE）缩短至5毫秒。即使对于更快的心率，这在重新调整血流信号的相位方面也是有效的。通过减小体素大小可进一步最小化相移。低至2毫米的层厚也提高了解剖分辨率。15毫秒的重复时间（TR）为动态研究提供了高时间分辨率。对血流重新调整梯度回波序列的修改允许测量大动脉中的血流并计算血流量，以评估左右心室的每搏输出量。这也可以通过从整个心脏的连续切片计算心室容积来实现；然而，这会导致测量时间过长。与传统的自旋回波技术相比，解剖分析得到了改善。房间隔缺损（ASD）的大小可以更精确地测量。自旋回波图像上无法检测到的小房间隔或室间隔缺损（VSD）在梯度回波图像上得以显示，并且可以对左右心室压力进行半定量估计。肺动脉和静脉与支气管结构明显区分，并可追踪到亚段水平。无需心电图门控，即可获得心血管系统感兴趣部位的连续切片，并成功用于二次血管造影重建。
