Measuring B1 distributions by B1 phase encoding.
Measuring B1 distributions by B1 phase encoding.
复制标题
通过B1相编码测量B1分布。
DOI：
10.1002/mrm.26114
复制
发表时间：
2017-01
影响因子：
3.3
通讯作者：
Kerr AB
中科院分区：
文献类型：
--
作者：
Jordanova KV;Nishimura DG;Kerr AB
我们提出了一种通过在 B1 而不是图像空间中编码来获取 B1 分布图的方法。使用该方法，以不同于传统空间B1映射的方式获取B1数据，并且可以快速测量高动态范围B1数据。为了在 B1 中进行编码，我们获取切片的多个投影，每个投影都沿着相同的方向，但对 B1 使用不同的相位灵敏度。使用凸优化公式，我们重建切片的 B1 分布估计的直方图。我们通过将测量的分布与使用地球移动器距离 (EMD) 从参考空间 B1 地图计算的分布进行比较来验证体内 B1 分布测量。使用表面线圈的体模测量表明，对于增加的空间 B1 变化，使用所提出的方法测量的 B1 分布比低分辨率空间 B1 图更准确地估计分布，从而在使用较少测量的情况下使 EMD 降低 37%。我们提出并验证了一种无需获取空间 B1 地图即可直接获取 B1 分布信息的方法的性能。该方法可以为不需要空间 B1 定位的应用提供 B1 场的更快估计，例如扫描仪的发射增益校准，特别是对于高动态 B1 范围。
We propose a method to acquire B1 distribution plots by encoding in B1 instead of image space. Using this method, B1 data is acquired in a different way from traditional spatial B1 mapping, and allows for quick measurement of high dynamic range B1 data. To encode in B1, we acquire multiple projections of a slice, each along the same direction, but using a different phase sensitivity to B1. Using a convex optimization formulation, we reconstruct histograms of the B1 distribution estimates of the slice. We verify in vivo B1 distribution measurements by comparing measured distributions to distributions calculated from reference spatial B1 maps using the Earth Mover’s Distance (EMD). Phantom measurements using a surface coil show that for increased spatial B1 variations, measured B1 distributions using the proposed method more accurately estimate the distribution than a low-resolution spatial B1 map, resulting in a 37% EMD decrease while using fewer measurements. We propose and validate the performance of a method to acquire B1 distribution information directly without acquiring a spatial B1 map. The method may provide faster estimates of a B1 field for applications that do not require spatial B1 localization, such as the transmit gain calibration of the scanner, particularly for high dynamic B1 ranges.