Chang Zheng, Xiang Qing-San, Ji Jim, Yin Fang-Fang
Department of Radiation Oncology, Duke University, Durham, North Carolina 27710, USA.
Magn Reson Med. 2009 Jan;61(1):229-33. doi: 10.1002/mrm.21809.
The fast MRI method of Skipped Phase Encoding and Edge Deghosting (SPEED) is further developed to accelerate multiple acquisitions. In a single acquisition, SPEED first acquires three sparse ghosted edge maps with an undersampling factor of N/3, which are modeled with a double-layer structure and described by three equations with two unknown ghosts, each with a unique ghost order index. By minimizing least-square-error, a pair of ghost order indexes is determined. Based on them, the two corresponding ghosts are resolved, leading to a deghosted image. In this case, three equations are needed to determine the ghost order index, while only two equations are required to resolve the two ghosts. This shows both inefficiency and potential. Multiple acquisitions often contain similar spatial information. The similarities can be used to improve efficiency by sharing the ghost order index among different acquisitions, leading to acceleration factors greater than that achievable with single acquisition.
跳跃相位编码和边缘去鬼影快速磁共振成像方法（SPEED）被进一步开发以加速多次采集。在单次采集中，SPEED首先以N/3的欠采样因子采集三张稀疏的带鬼影边缘图，这些图采用双层结构建模，并由三个包含两个未知鬼影的方程描述，每个鬼影都有一个独特的鬼影阶数索引。通过最小化最小二乘误差，确定一对鬼影阶数索引。基于这些索引，解析出两个相应的鬼影，从而得到去鬼影图像。在这种情况下，需要三个方程来确定鬼影阶数索引，而仅需两个方程来解析两个鬼影。这既显示出效率低下，也显示出潜力。多次采集通常包含相似的空间信息。这些相似性可通过在不同采集之间共享鬼影阶数索引来提高效率，从而实现比单次采集更高的加速因子。
