Fast and tissue-optimized mapping of magnetic susceptibility and T2* with multi-echo and multi-shot spirals.
Fast and tissue-optimized mapping of magnetic susceptibility and T2* with multi-echo and multi-shot spirals.
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DOI：
10.1016/j.neuroimage.2011.07.019
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发表时间：
2012-01-02
期刊：
影响因子：
5.7
通讯作者：
Liu, Chunlei
中科院分区：
文献类型：
--
作者：
Wu, Bing;Li, Wei;Avram, Alexandru Vlad;Gho, Sung-Min;Liu, Chunlei
共振频移和T2* 值的磁共振回波MRI表现出独特的组织对比度，并提供相关的生理信息。然而，对于高空间分辨率和全脑覆盖的常规成像，使用标准扰相梯度回波（SPGR）序列采集3D相位图像和T2* 图[A1]的时间较长。此外，对于标准SPGR序列，给定其分布的共振频率和T2* 值，不能针对每种组织类型实现最佳信噪比（SNR）。为了解决这两个问题，提出并实现了具有螺旋堆叠采集的SNR优化的多回波序列，用于实现图像相位和T2* 图的快速和同时采集。相位SNR的分析行为是作为谐振频率、T2* 和回波时间的函数导出的。该关系用于通过组合具有不同回波时间的相位图像来实现组织优化的SNR。模拟和体内实验的设计，以验证理论预测。使用多回波螺旋采集，可以在2.5分钟内实现1 mm各向同性分辨率的全脑覆盖，将扫描时间缩短8倍。得到的多回波相位图显示出与标准SPGR相似的SNR。可以通过非笛卡尔并行成像进一步加速采集。该技术可以很容易地扩展到其他多炮读出轨迹除了螺旋。它可以提供一个实用的采集策略，高分辨率和同时三维映射的磁化率和T2*。
Gradient-echo MRI of resonance-frequency shift and T2* values exhibits unique tissue contrast and offers relevant physiological information. However, acquiring 3D-phase images and T2* maps [A1] with the standard spoiled gradient echo (SPGR) sequence is lengthy for routine imaging at high-spatial resolution and whole-brain coverage. In addition, with the standard SPGR sequence, optimal signal-to-noise ratio (SNR) cannot be achieved for every tissue type given their distributed resonance frequency and T2* value. To address these two issues, a SNR optimized multi-echo sequence with a stack-of-spiral acquisition is proposed and implemented for achieving fast and simultaneous acquisition of image phase and T2* maps. The analytical behavior of the phase SNR is derived as a function of resonance frequency, T2* and echo time. This relationship is utilized to achieve tissue optimized SNR by combining phase images with different echo times. Simulations and in vivo experiments were designed to verify the theoretical predictions. Using the multi-echo spiral acquisition, whole-brain coverage with 1 mm isotropic resolution can be achieved within 2.5 minutes, shortening the scan time by a factor of 8. The resulting multi-echo phase map shows similar SNR to that of the standard SPGR. The acquisition can be further accelerated with non-Cartesian parallel imaging. The technique can be readily extended to other multi-shot readout trajectories besides spiral. It may provide a practical acquisition strategy for high resolution and simultaneous 3D mapping of magnetic susceptibility and T2*.
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影响因子：
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