Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland. Center for Medical Image Analysis & Navigation, University of Basel, Allschwil, Switzerland.
Phys Med Biol. 2018 Jul 16;63(14):145015. doi: 10.1088/1361-6560/aaca1d.
We present an ultrasound-driven 4D magnetic resonance imaging (US-4DMRI) method for respiratory motion imaging in the thorax and abdomen. The proposed US-4DMRI comes along with a high temporal resolution, and allows for organ motion imaging beyond a single respiratory cycle. With the availability of the US surrogate both inside and outside the MR bore, 4D MR images can be reconstructed for 4D treatment planning and online respiratory motion prediction during radiotherapy. US-4DMRI relies on simultaneously acquired 2D liver US images and abdominal 2D MR multi-slice scans under free respiration. MR volumes are retrospectively composed by grouping the MR slices corresponding to the most similar US images. We present two different US similarity metrics: an intensity-based approach, and a similarity measure relying on predefined fiducials which are being tracked over time. The proposed method is demonstrated on MR liver scans of eight volunteers acquired over a duration of 5.5 min each at a temporal resolution of 2.6 Hz with synchronous US imaging at 14 Hz-17 Hz. Visual inspection of the reconstructed MR volumes revealed satisfactory results in terms of continuity in organ boundaries and blood vessels. In quantitative leave-one-out experiments, both US similarity metrics reach the performance level of state-of-the-art navigator-based approaches.
我们提出了一种基于超声的 4D 磁共振成像（US-4DMRI）方法，用于胸部和腹部的呼吸运动成像。所提出的 US-4DMRI 具有高时间分辨率，并允许在单个呼吸周期之外进行器官运动成像。由于在 MR 孔径内外都可以使用 US 替代物，因此可以重建 4DMR 图像，以便在放射治疗期间进行 4D 治疗计划和在线呼吸运动预测。US-4DMRI 依赖于在自由呼吸下同时采集的 2D 肝脏 US 图像和腹部 2D MR 多切片扫描。通过将与最相似的 US 图像相对应的 MR 切片分组，MR 体积可以被回溯性地构建。我们提出了两种不同的 US 相似度度量：一种基于强度的方法，和一种依赖于随时间跟踪的预定义基准的相似度度量。所提出的方法在八位志愿者的 MR 肝脏扫描上进行了演示，每个志愿者的扫描持续时间为 5.5 分钟，时间分辨率为 2.6Hz，同时以 14Hz-17Hz 的频率进行同步 US 成像。对重建的 MR 体积进行视觉检查，结果显示在器官边界和血管的连续性方面令人满意。在定量的 leave-one-out 实验中，两种 US 相似度度量都达到了基于导航仪的最新方法的性能水平。
