McKenzie C A, Ohliger M A, Yeh E N, Price M D, Sodickson D K
Department of Medicine, Cardiovascular Division, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
Magn Reson Med. 2001 Sep;46(3):619-23. doi: 10.1002/mrm.1236.
The SiMultaneous Acquisition of Spatial Harmonics (SMASH) technique uses linear combinations of undersampled datasets from the component coils of an RF coil array to reconstruct fully sampled composite datasets in reduced imaging times. In previously reported implementations, SMASH reconstructions were designed to reproduce the images that would otherwise be obtained by simple sums of fully gradient encoded component coil images. This strategy has left SMASH images vulnerable to phase cancellation artifacts when the sensitivities of RF coil array elements are not suitably phase-aligned. In fully gradient encoded imaging schemes these artifacts can be eliminated using a variety of methods for combining the individual coil images, including matched filter combinations as well as sum of squares combinations. Until now, these reconstruction schemes have been unavailable to SMASH reconstructions as SMASH produced a final composite image directly from the raw component coil k-space datasets. This article demonstrates a modification to SMASH that allows reconstruction of a full set of accelerated individual component coil images by fitting component coil sensitivity functions to a complete set of spatial harmonics tailored for each coil in the array. Standard component coil combinations applied to the individual reconstructed images produce final composite images free of phase cancellation artifacts.
空间谐波同步采集（SMASH）技术利用射频线圈阵列各组成线圈欠采样数据集的线性组合，在更短的成像时间内重建全采样复合数据集。在先前报道的实现方法中，SMASH重建旨在重现通过对完全梯度编码的各组成线圈图像进行简单求和而获得的图像。当射频线圈阵列元件的灵敏度未进行适当的相位对齐时，这种策略会使SMASH图像容易出现相位抵消伪影。在完全梯度编码成像方案中，可使用多种组合单个线圈图像的方法消除这些伪影，包括匹配滤波器组合以及平方和组合。到目前为止，这些重建方案无法用于SMASH重建，因为SMASH是直接从原始组成线圈k空间数据集生成最终复合图像的。本文展示了对SMASH的一种改进，即通过将组成线圈灵敏度函数拟合到为阵列中每个线圈量身定制的一组完整空间谐波，来重建一组完整的加速单个组成线圈图像。应用于各个重建图像的标准组成线圈组合可生成无相位抵消伪影的最终复合图像。
