Stanford University, David Packard Electrical Engineering 350 Serra Mall, Rm. 308, Stanford, California, USA.
Magn Reson Med. 2018 Jun;79(6):2944-2953. doi: 10.1002/mrm.26957. Epub 2017 Oct 10.
To mitigate artifacts from through-plane flow at the locations of steady-state stopbands in balanced steady-state free precession (SSFP) using partial dephasing.
A 60° range in the phase accrual during a TR was created over the voxel by slightly unbalancing the slice-select dephaser. The spectral profiles of SSFP with partial dephasing for various constant flow rates and during pulsatile flow were simulated to determine if partial dephasing decreases through-plane flow artifacts originating near SSFP dark bands while maintaining on-resonant signal. Simulations were then validated in a flow phantom. Lastly, phase-cycled SSFP cardiac cine images were acquired with and without partial dephasing in six subjects.
Partial dephasing decreased the strength and non-linearity of the dependence of the signal at the stopbands on the through-plane flow rate. It thus mitigated hyper-enhancement from out-of-slice signal contributions and transient-related artifacts caused by variable flow both in the phantom and in vivo. In six volunteers, partial dephasing noticeably decreased artifacts in all of the phase-cycled cardiac cine datasets.
Partial dephasing can mitigate the flow artifacts seen at the stopbands in balanced SSFP while maintaining the sequence's desired signal. By mitigating hyper-enhancement and transient-related artifacts originating from the stopbands, partial dephasing facilitates robust multiple-acquisition phase-cycled SSFP in the heart. Magn Reson Med 79:2944-2953, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
通过部分去相位来减轻稳态自由进动（SSFP）中的稳定静带位置的平面内流动伪影。
通过稍微不平衡切片选择去相器，在 TR 期间在体素中创建 60°的相位积累范围。模拟具有部分去相位的 SSFP 的光谱曲线，用于各种恒定流速和脉动流，以确定部分去相位是否在保持共振信号的同时减少源自 SSFP 暗带附近的平面内流动伪影。然后在流动体模中验证了模拟结果。最后，在六个对象中分别采集了具有和不具有部分去相位的相位循环 SSFP 心脏电影图像。
部分去相位降低了在静带处的信号对平面内流速的依赖性的强度和非线性。因此，它减轻了来自切片外信号贡献的超增强以及在体模和体内由可变流动引起的与瞬变相关的伪影。在六个志愿者中，相位循环心脏电影数据集中的所有部分去相位都明显降低了伪影。
部分去相位可以减轻平衡 SSFP 中静带处的流动伪影，同时保持序列所需的信号。通过减轻源自静带的超增强和与瞬变相关的伪影，部分去相位有助于在心脏中进行稳健的多采集相位循环 SSFP。磁共振医学 79：2944-2953，2018。© 2017 国际磁共振学会。
