FAST MULTISLICE B1 MAPPING: MRI

攻略：B1场应用的不均一性妥协 磁共振测量的准确性。这种不均质性取决于 射频线圈、负载和被观测对象的特性[1]。一个 B1字段的映射使解释和更正成为可能 与射频不均匀性相关的问题，例如图像伪影 或者量化不准确。方法：在我们的方法中，一个受刺激的 回声序列(STE)被修改为附加的非选择性 脉搏。由于观察到的信号和 额外脉冲的翻转角，我们可以稳健地估计 B1.在1.5-T GE Signa系统上测量多层B1-MAP 标准圆极化磁头线圈。直径28厘米的球体 在射频线圈的中心放置含有掺杂的水。四 在名义theta设置为0,100的情况下，获取7个切片的集合， 200度和300度。总成像时间为2：20min。结果： 从模体和正常体模获得多层定量B1图 志愿者。这些图证实了预期的头部B1变异 线圈。结论：射频的快速定量容量估计 可以使用修改后的 刺激回声序列。

Introduction: Inhomogeneity of the applied B1 field compromises the accuracy of MR-measurements. The inhomogeneity depends on the RF-coil, the load, and characteristics of the observed object [1]. A map of the B1 field makes it possible to account for and correct problems associated with the RF-inhomogeneity, such as image artifacts or inaccurate quantization. Methods: In our method, a stimulated echo sequence (STE) is modified with an additional non-selective pulse. Due to the simple relationship between the observed signal and the flip angle, theta, of the extra pulse, we can robustly estimate B1. Multislice B1-maps were measured on a 1.5-T GE Signa system using the standard circularly polarized head coil. A 28-cm diameter sphere containing doped water was placed in the center of the RF-coil. Four sets of 7 slices were acquired with the nominal theta set to 0, 100, 200, and 300 degrees. Total imaging time was 2:20 min. Results: Multislice quantitative B1 maps were acquired from phantoms and normal volunteers. The maps confirm the exptected B1 variations of the head coil. Conclusions: Rapid quantitative volumetric estimates of RF profiles can be calculated from acquisitions with a modified stimulated-echo sequence.