Spatiotemporal motion estimation for respiratory-correlated imaging of the lungs
Spatiotemporal motion estimation for respiratory-correlated imaging of the lungs
复制标题
DOI：
10.1118/1.3523619
复制
发表时间：
2011-01-01
期刊：
影响因子：
3.8
通讯作者：
Sarrut, David
中科院分区：
文献类型：
--
作者：
Vandemeulebroucke, Jef;Rit, Simon;Sarrut, David
目的：四维计算机断层扫描（4D CT）可以为放疗计划和放疗交付提供患者特有的运动信息。由于图像质量降低和伪影的存在，4D CT中的运动估计具有挑战性。我们的目标是通过使用全局问题公式和追求时空变形模型的限制性参数化，提高可变形配准应用于肺部呼吸相关成像的鲁棒性。方法：将基于自由变形的空间变换扩展到时域，利用基于b样条的循环时间模型对轨迹进行显式建模。全局配准准则允许同时考虑整个图像序列，并在整个呼吸周期中强制变形的时间相干性。为了确保参数化能够捕获呼吸运动的动力学，分别对时间维度进行了预研究。通过将时间参数拟合到大量患者的膈肌运动数据来调整时间参数。保留合适的属性并应用于4D CT数据的时空配准。注册结果使用大量的地标进行验证，并与连续的空间注册进行比较。为了说明时空方法的好处，我们还评估了在运动诱发伪影存在下的性能。结果：三次b样条作为低阶的拟合结果更好或相似，因为其固有的更强的正则化而被选择。随着时间控制点间距的增加，拟合和配准误差逐渐增加，这代表了可实现精度与对噪声和伪影的敏感性之间的权衡。一个分段平滑轨迹模型，允许在吸气末速度的不连续变化，被发现最适合解释在这个呼吸阶段运动的突然变化。时空建模允许减少45%的参数数量，同时保持0.1 mm以内的配准精度。该方法降低了对伪影的敏感性。结论：时空配准可以为4D CT提供准确的运动估计，提高对伪影的鲁棒性。(C) 2011年美国医学物理学家协会。(DOI: 10.1118/1.3523619)
Purpose: Four-dimensional computed tomography (4D CT) can provide patient-specific motion information for radiotherapy planning and delivery. Motion estimation in 4D CT is challenging due to the reduced image quality and the presence of artifacts. We aim to improve the robustness of deformable registration applied to respiratory-correlated imaging of the lungs, by using a global problem formulation and pursuing a restrictive parametrization for the spatiotemporal deformation model.Methods: A spatial transformation based on free-form deformations was extended to the temporal domain, by explicitly modeling the trajectory using a cyclic temporal model based on B-splines. A global registration criterion allowed to consider the entire image sequence simultaneously and enforce the temporal coherence of the deformation throughout the respiratory cycle. To ensure a parametrization capable of capturing the dynamics of respiratory motion, a prestudy was performed on the temporal dimension separately. The temporal parameters were tuned by fitting them to diaphragm motion data acquired for a large patient group. Suitable properties were retained and applied to spatiotemporal registration of 4D CT data. Registration results were validated using large sets of landmarks and compared to consecutive spatial registrations. To illustrate the benefit of the spatiotemporal approach, we also assessed the performance in the presence of motion-induced artifacts.Results: Cubic B-splines gave better or similar fitting results as lower orders and were selected because of their inherently stronger regularization. The fitting and registration errors increased gradually with the temporal control point spacing, representing a trade-off between achievable accuracy and sensitivity to noise and artifacts. A piecewise smooth trajectory model, allowing for a discontinuous change of speed at end-inhale, was found most suitable to account for the sudden changes of motion at this breathing phase. The spatiotemporal modeling allowed a reduction of the number of parameters of 45%, while maintaining registration accuracy within 0.1 mm. The approach reduced the sensitivity to artifacts.Conclusions: Spatiotemporal registration can provide accurate motion estimation for 4D CT and improves the robustness to artifacts. (C) 2011 American Association of Physicists in Medicine. [DOI: 10.1118/1.3523619]