使用旋转笛卡尔 k 空间（ROCK）的呼吸运动分辨、自门控 4D-MRI
Respiratory motion-resolved, self-gated 4D-MRI using rotating cartesian k-space (ROCK).
作者信息
Han Fei, Zhou Ziwu, Cao Minsong, Yang Yingli, Sheng Ke, Hu Peng
机构信息
Department of Radiological Sciences, David Geffen School of Medicine, University of California, 300 UCLA Medical Plaza Suite B119, Los Angeles, CA 90095, USA.
Department of Bioengineering, University of California, 300 UCLA Medical Plaza Suite B119, Los Angeles, CA 90095, USA.
出版信息
Med Phys. 2017 Apr;44(4):1359-1368. doi: 10.1002/mp.12139. Epub 2017 Mar 11.
PURPOSE
To propose and validate a respiratory motion resolved, self-gated (SG) 4D-MRI technique to assess patient-specific breathing motion of abdominal organs for radiation treatment planning.
METHODS
The proposed 4D-MRI technique was based on the balanced steady-state free-precession (bSSFP) technique and 3D k-space encoding. A novel rotating cartesian k-space (ROCK) reordering method was designed which incorporates repeatedly sampled k-space centerline as the SG motion surrogate and allows for retrospective k-space data binning into different respiratory positions based on the amplitude of the surrogate. The multiple respiratory-resolved 3D k-space data were subsequently reconstructed using a joint parallel imaging and compressed sensing method with spatial and temporal regularization. The proposed 4D-MRI technique was validated using a custom-made dynamic motion phantom and was tested in six healthy volunteers, in whom quantitative diaphragm and kidney motion measurements based on 4D-MRI images were compared with those based on 2D-CINE images.
RESULTS
The 5-minute 4D-MRI scan offers high-quality volumetric images in 1.2 × 1.2 × 1.6 mm and eight respiratory positions, with good soft-tissue contrast. In phantom experiments with triangular motion waveform, the motion amplitude measurements based on 4D-MRI were 11.89% smaller than the ground truth, whereas a -12.5% difference was expected due to data binning effects. In healthy volunteers, the difference between the measurements based on 4D-MRI and the ones based on 2D-CINE were 6.2 ± 4.5% for the diaphragm, 8.2 ± 4.9% and 8.9 ± 5.1% for the right and left kidney.
CONCLUSION
The proposed 4D-MRI technique could provide high-resolution, high-quality, respiratory motion-resolved 4D images with good soft-tissue contrast and are free of the "stitching" artifacts usually seen on 4D-CT and 4D-MRI based on resorting 2D-CINE. It could be used to visualize and quantify abdominal organ motion for MRI-based radiation treatment planning.
目的
提出并验证一种呼吸运动分辨的自门控（SG）4D-MRI技术，以评估腹部器官的患者特异性呼吸运动，用于放射治疗计划。
方法
所提出的4D-MRI技术基于平衡稳态自由进动（bSSFP）技术和3D k空间编码。设计了一种新颖的旋转笛卡尔k空间（ROCK）重排序方法，该方法将重复采样的k空间中心线作为SG运动替代物，并允许基于替代物的幅度将回顾性k空间数据分箱到不同的呼吸位置。随后使用具有空间和时间正则化的联合并行成像和压缩感知方法重建多个呼吸分辨的3D k空间数据。使用定制的动态运动体模对所提出的4D-MRI技术进行了验证，并在六名健康志愿者中进行了测试，将基于4D-MRI图像的定量膈肌和肾脏运动测量结果与基于2D-CINE图像的测量结果进行了比较。
结果
5分钟的4D-MRI扫描可提供1.2×1.2×1.6 mm和八个呼吸位置的高质量容积图像，具有良好的软组织对比度。在具有三角运动波形的体模实验中，基于4D-MRI的运动幅度测量结果比真实值小11.89%，而由于数据分箱效应，预期差异为-12.5%。在健康志愿者中，基于4D-MRI的测量结果与基于2D-CINE的测量结果之间，膈肌的差异为6.2±4.5%，右肾和左肾的差异分别为8.2±4.9%和8.9±5.1%。
结论
所提出的4D-MRI技术可以提供高分辨率、高质量、呼吸运动分辨的4D图像，具有良好的软组织对比度，并且没有通常在基于2D-CINE重排的4D-CT和4D-MRI上看到的“拼接”伪影。它可用于可视化和量化基于MRI的放射治疗计划中的腹部器官运动。
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