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首页> 外文期刊>IEEE Transactions on Medical Imaging >Self-Navigated Three-Dimensional Ultrashort Echo Time Technique for Motion-Corrected Skull MRI
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Self-Navigated Three-Dimensional Ultrashort Echo Time Technique for Motion-Corrected Skull MRI

机译：运动校正颅骨MRI的自化三维超短回声时间技术

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Ultrashort echo time (UTE) MRI is capable of detecting signals from protons with very short T-2 relaxation times, and thus has potential for skull-selective imaging as a radiation-free alternative to computed tomography. However, relatively long scan times make the technique vulnerable to artifacts from involuntary subject motion. Here, we developed a self-navigated, three-dimensional (3D) UTE pulse sequence, which builds on dual-RF, dual-echo UTE imaging, and a retrospective motion correction scheme for motion-resistant skull MRI. Full echo signals in the second readout serve as a self-navigator that yields a time-course of center of mass, allowing for adaptive determination of motion states. Furthermore, golden-means based k-space trajectory was employed to achieve a quasi-uniform distribution of sampling views on a spherical k-space surface for any subset of the entire data collected, thereby allowing reconstruction of low-resolution images pertaining to each motion state for subsequent estimation of rigid-motion parameters. Finally, the extracted trajectory of the head was used to make the whole k-space datasets motion-consistent, leading to motion-corrected, high-resolution images. Additionally, we posit that hardware-related k-space trajectory errors, if uncorrected, result in obscured bone contrast. Thus, a calibration scan was performed once to measure k-space encoding locations, subsequently used during image reconstruction of actual imaging data. In vivo studies were performed to evaluate the effectiveness of the proposed correction schemes in combination with approaches to accelerated bone-selective imaging. Results illustrating effective removal of motion artifacts and clear depiction of skull bone voxels suggest that the proposed method is robust to intermittent head motions during scanning.
机译：Ultrashort回波时间（UTE）MRI能够检测具有非常短的T-2松弛时间的质子的信号，因此具有颅骨选择性成像作为对计算机断层摄影的无辐射替代的潜力。然而，相对长的扫描时间使得该技术容易受到非自愿对象运动的伪影。在这里，我们开发了一种自行的三维（3D）UTE脉冲序列，它在双RF，双回声UTE成像和用于运动颅骨MRI的回顾性运动校正方案上构建。第二读数中的完整回声信号用作自导航器，产生质量中心的时间过程，允许自适应确定运动状态。此外，采用金属基于金属的k空间轨迹来实现对选集的所有数据的任何子集的球面k空间表面上的采样视图的准均匀分布，从而允许重建与每个运动有关的低分辨率图像后续估计刚性运动参数的状态。最后，用于使头的提取轨迹用于使整个K空间数据集进行运动 - 一致，导致运动校正的高分辨率图像。此外，如果未经校正，我们将其与硬​​件相关的k空间轨迹错误有关，导致骨骼对比度。因此，一次执行校准扫描一次以测量k空间编码位置，随后在实际成像数据的图像重建期间使用。进行体内研究以评估所提出的校正方案的有效性与加速骨选择性成像的方法组合。结果说明有效地去除运动伪影和颅骨骨体素的透明描绘表明，该方法在扫描过程中对间歇性的头部运动是鲁棒的。

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