Purpose: Commonly used diffusion weighted (DW) imaging such as DW spin echo (SE) type echo planar imaging (DW-SE-EPI) is known to be a snapshot-like acquisition and to have a relatively high signal-to-noise ratio. Spi...Purpose: Commonly used diffusion weighted (DW) imaging such as DW spin echo (SE) type echo planar imaging (DW-SE-EPI) is known to be a snapshot-like acquisition and to have a relatively high signal-to-noise ratio. Spiral MRI sequence (SPIRAL) has characteristics similar to these of EPI, but it has rarely been used for diffusion-weighted imaging (DWI). In vivo DW-SPIRAL of the rat brain has almost never been reported. Our purpose in this study was to examine the potential of SE-type two-dimensional (2D) multi-shot spiral acquisition MRI for apparent diffusion coefficient (ADC) mapping of the rat brain in vivo. Materials and Methods: We made an SE-type DW-2D-spiral MRI sequence (DW-SPIRAL) which was prepared on a 2.0-T animal-experiment MR scanner. Comparing the phantom experimental result of DW-SPIRAL with the phantom experimental result of DW SE-type echo-planar imaging (DW-SE-EPI) and conventional DW spin echo imaging (DW-SE), we estimated the characteristics of DW-SPIRAL and assessed the clinical application of DW-SPIRAL in an animal experiment on the rat brain. Results: There was not much difference between the calculated water/glycerol phantom diffusion coefficient of DW-SPIRAL and the calculated diffusion coefficient of DW-SE. This result shows that the DW-SPIRAL sequence is appropriate for use in diffusion weighted imaging. There were fewer phantom image distortions and ghosting artifacts with DW-SPIRAL than with DW-SE-EPI, and this tendency was similar in the animal experiment on the rat brain. Conclusion: The DW-SPIRAL sequence had been successfully tested in phantom experiments and rat brain experiments. It has been demonstrated that the DW-SPIRAL sequence is capable of producing in vivo rat brain DWI.展开更多
目前,人脑认知功能研究广泛使用平面回波成像(EPI)来快速扫描全脑。然而,EPI采用笛卡尔轨迹覆盖k空间,其读出持续时间较长,对运动的敏感性高。该文介绍另外一种快速成像技术——螺旋成像(spiral imaging)。Spiral用阿基米德或类似轨迹覆...目前,人脑认知功能研究广泛使用平面回波成像(EPI)来快速扫描全脑。然而,EPI采用笛卡尔轨迹覆盖k空间,其读出持续时间较长,对运动的敏感性高。该文介绍另外一种快速成像技术——螺旋成像(spiral imaging)。Spiral用阿基米德或类似轨迹覆盖k空间,其读出持续时间短,对运动的敏感性低。Spiral有望突破EPI在脑认知功能研究中的瓶颈,具体表现为内、外螺旋(spiral-in/out)能够在减少磁敏感性脑区信号衰减的同时增加磁敏感性均匀脑区的信噪比,变化密度螺旋(variable density spiral)可以在保持信噪比的条件下实现单次激发Spiral的高时空分辨扫描。展开更多
文摘Purpose: Commonly used diffusion weighted (DW) imaging such as DW spin echo (SE) type echo planar imaging (DW-SE-EPI) is known to be a snapshot-like acquisition and to have a relatively high signal-to-noise ratio. Spiral MRI sequence (SPIRAL) has characteristics similar to these of EPI, but it has rarely been used for diffusion-weighted imaging (DWI). In vivo DW-SPIRAL of the rat brain has almost never been reported. Our purpose in this study was to examine the potential of SE-type two-dimensional (2D) multi-shot spiral acquisition MRI for apparent diffusion coefficient (ADC) mapping of the rat brain in vivo. Materials and Methods: We made an SE-type DW-2D-spiral MRI sequence (DW-SPIRAL) which was prepared on a 2.0-T animal-experiment MR scanner. Comparing the phantom experimental result of DW-SPIRAL with the phantom experimental result of DW SE-type echo-planar imaging (DW-SE-EPI) and conventional DW spin echo imaging (DW-SE), we estimated the characteristics of DW-SPIRAL and assessed the clinical application of DW-SPIRAL in an animal experiment on the rat brain. Results: There was not much difference between the calculated water/glycerol phantom diffusion coefficient of DW-SPIRAL and the calculated diffusion coefficient of DW-SE. This result shows that the DW-SPIRAL sequence is appropriate for use in diffusion weighted imaging. There were fewer phantom image distortions and ghosting artifacts with DW-SPIRAL than with DW-SE-EPI, and this tendency was similar in the animal experiment on the rat brain. Conclusion: The DW-SPIRAL sequence had been successfully tested in phantom experiments and rat brain experiments. It has been demonstrated that the DW-SPIRAL sequence is capable of producing in vivo rat brain DWI.
文摘目前,人脑认知功能研究广泛使用平面回波成像(EPI)来快速扫描全脑。然而,EPI采用笛卡尔轨迹覆盖k空间,其读出持续时间较长,对运动的敏感性高。该文介绍另外一种快速成像技术——螺旋成像(spiral imaging)。Spiral用阿基米德或类似轨迹覆盖k空间,其读出持续时间短,对运动的敏感性低。Spiral有望突破EPI在脑认知功能研究中的瓶颈,具体表现为内、外螺旋(spiral-in/out)能够在减少磁敏感性脑区信号衰减的同时增加磁敏感性均匀脑区的信噪比,变化密度螺旋(variable density spiral)可以在保持信噪比的条件下实现单次激发Spiral的高时空分辨扫描。
