Department of Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany.
Magn Reson Med. 2011 Aug;66(2):402-9. doi: 10.1002/mrm.22803. Epub 2011 Mar 4.
Parallel imaging based on generalized autocalibrating partially parallel acquisitions is widely used in the clinical routine. To date, no detailed analysis has been presented describing the dependence of the image quality on the reconstruction and acquisition parameters such as the number of autocalibration signal (ACS) lines NACS, the reconstruction kernel size (bx×by), and the undersampling factor R. To evaluate their influence on the performance of generalized autocalibrating partially parallel acquisitions, two phantom data sets acquired with 12-channel and 32-channel receive coils and three in vivo measurements were analyzed. Reconstruction parameters were systematically varied between R=2-4, NACS=4-64, bx=1-9, and by=2-10 to characterize their influence on image quality and noise. A main aspect of the analysis was to optimize the parameter set with respect to the effectively achieved net image acceleration. Selecting the undersampling factor R as small as possible for a given net acceleration yielded the best result in a clear majority of cases. For all data sets and coil geometries, the optimal kernel sizes and number of ACS lines were similar for a chosen undersampling factor R. In summary, the number of ACS lines should not be chosen below NACS=10-16. A robust choice for the kernel size was bx=9 and by=2-4.
基于广义自校准部分并行采集的并行成像广泛应用于临床常规。迄今为止，还没有详细的分析描述重建和采集参数（如自动校准信号 (ACS) 线数量 NACS、重建核大小 (bx×by) 和欠采样因子 R）对图像质量的依赖关系。为了评估它们对广义自校准部分并行采集性能的影响，分析了两个使用 12 通道和 32 通道接收线圈以及三个体内测量采集的体模数据集。在 R=2-4、NACS=4-64、bx=1-9 和 by=2-10 之间系统地改变重建参数，以表征它们对图像质量和噪声的影响。分析的一个主要方面是针对有效实现的净图像加速来优化参数集。在给定的净加速下，尽可能选择较小的欠采样因子 R 可在绝大多数情况下获得最佳结果。对于所有数据集和线圈几何形状，对于给定的欠采样因子 R，最佳核大小和 ACS 线数量相似。总之，ACS 线的数量不应低于 NACS=10-16。核大小的稳健选择是 bx=9 和 by=2-4。
