Irarrazabal P, Meyer C H, Nishimura D G, Macovski A
Department of Electrical Engineering, Stanford University, California, USA.
Magn Reson Med. 1996 Feb;35(2):278-82. doi: 10.1002/mrm.1910350221.
A fast and robust method for correcting magnetic resonance image distortion due to field inhomogeneity is proposed and applied to spiral k-space scanning. The method consists of acquiring a local field map, finding the best fit to a linear map, and using it to deblur the image distortions due to local frequency variations. The linear field map is determined using a maximum likelihood estimator with weights proportional to the pixel intensity. The method requires little additional computation and is robust in low signal regions and near abrupt field changes. Additionally, it can be used in combination with other deblurring methods. The application of this method is illustrated in conjunction with a multislice, T2-weighted, breath-held spiral scan of the liver.
提出了一种快速且稳健的方法来校正由于场不均匀性导致的磁共振图像失真，并将其应用于螺旋k空间扫描。该方法包括获取局部场图、找到与线性图的最佳拟合，并使用它来消除由于局部频率变化引起的图像失真。线性场图使用与像素强度成比例加权的最大似然估计器来确定。该方法几乎不需要额外的计算，并且在低信号区域和接近场突变处具有稳健性。此外，它可以与其他去模糊方法结合使用。结合肝脏的多层、T2加权、屏气螺旋扫描说明了该方法的应用。
