FAST MULTISLICE B1 MAPPING: MRI

简介：所施加的B1场的不均匀性 MR测量的准确性。 不均匀性取决于 RF线圈、负载和观察对象的特性[1]。 一 B1字段的映射可以解释和纠正 与RF不均匀性相关的问题，如图像伪影 或不精确的量化。 方法：在我们的方法中， 回波序列（STE）被修改为额外的非选择性 脉搏了 由于观察到的信号与 额外脉冲的翻转角θ，我们可以很好地估计 B1. 在1.5-T GE Signa系统上测量多层B1图，使用 标准的圆极化头部线圈 一个直径28厘米的球体 将含有掺杂水的混合物放置在RF线圈的中心。 四 在标称θ设定为0，100， 200到300度。 总成像时间为2：20 min。结果： 多层定量B1图从模型和正常获得 志愿者 这些图证实了头部的预期B1变化 线圈 结论：RF的快速定量体积估计 可以使用修改后的 受激回波序列

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.