Jezzard P, Balaban R S
Laboratory of Cardiac Energetics, NHLBI, National Institutes of Health, Bethesda, MD 20892, USA.
Magn Reson Med. 1995 Jul;34(1):65-73. doi: 10.1002/mrm.1910340111.
A method is described for the correction of geometric distortions occurring in echo planar images. The geometric distortions are caused in large part by static magnetic field inhomogeneities, leading to pixel shifts, particularly in the phase encode direction. By characterizing the field inhomogeneities from a field map, the image can be unwarped so that accurate alignment to conventionally collected images can be made. The algorithm to perform the unwarping is described, and results from echo planar images collected at 1.5 and 4 Tesla are shown.
描述了一种校正回波平面图像中出现的几何失真的方法。几何失真在很大程度上是由静磁场不均匀性引起的，导致像素移位，特别是在相位编码方向上。通过从场图中表征场不均匀性，可以对图像进行去扭曲，从而能够与传统采集的图像进行精确对齐。描述了执行去扭曲的算法，并展示了在1.5特斯拉和4特斯拉下采集的回波平面图像的结果。
