标题： 图像空间栅格化用于非刚性运动校正的MR图像重建 显示英文标题

标题： Image-Space Gridding for Nonrigid Motion-Corrected MR Image Reconstruction

摘要： 运动仍然是磁共振（MR）成像中的一个主要挑战，特别是在自由呼吸心脏MR成像中，数据是在多个心跳周期、不同呼吸阶段采集的。 我们采用基于模型的方法进行非刚性运动校正，解决两个挑战：（a）运动表示和（b）运动估计。 对于运动表示，我们通过适应非均匀快速傅里叶变换（NUFFT）推导出图像空间网格，以表示和计算非刚性运动，这提供了一个精确的前向伴随线性算子对。 然后我们引入非刚性SENSE算子，将非刚性运动纳入多线圈MR采集模型。 对于运动估计，我们使用低分辨率三维图像导航器（iNAVs）和高分辨率三维自导航图像导航器（self-iNAVs）。 在每个心跳期间，数据沿两种非笛卡尔轨迹采集：一种是稀疏覆盖三维k空间的高分辨率轨迹的子集，接着是一条完整的低分辨率轨迹。 我们使用完整的低分辨率数据重建每个心跳的三维iNAVs，这些数据随后用于估计整体运动并识别每个心跳的呼吸相位。 通过结合同一呼吸相位内多个心跳的数据，我们重建高分辨率三维自iNAVs，从而估算非刚性呼吸运动。 对于每个呼吸相位，我们构建非刚性SENSE算子，将非刚性运动校正重建重新表述为标准的正则化逆问题。 在初步研究中，所提出的方法增强了冠状动脉的清晰度，并改善了非心脏区域的图像质量，优于平移运动校正重建。 显示英文摘要

摘要： Motion remains a major challenge in magnetic resonance (MR) imaging, particularly in free-breathing cardiac MR imaging, where data are acquired over multiple heartbeats at varying respiratory phases. We adopt a model-based approach for nonrigid motion correction, addressing two challenges: (a) motion representation and (b) motion estimation. For motion representation, we derive image-space gridding by adapting the nonuniform fast Fourier transform (NUFFT) to represent and compute nonrigid motion, which provides an exact forward-adjoint pair of linear operators. We then introduce nonrigid SENSE operators that incorporate nonrigid motion into the multi-coil MR acquisition model. For motion estimation, we employ both low-resolution 3D image-based navigators (iNAVs) and high-resolution 3D self-navigating image-based navigators (self-iNAVs). During each heartbeat, data are acquired along two types of non-Cartesian trajectories: a subset of a high-resolution trajectory that sparsely covers 3D k-space, followed by a full low-resolution trajectory. We reconstruct 3D iNAVs for each heartbeat using the full low-resolution data, which are then used to estimate bulk motion and identify the respiratory phase of each heartbeat. By combining data from multiple heartbeats within the same respiratory phase, we reconstruct high-resolution 3D self-iNAVs, allowing estimation of nonrigid respiratory motion. For each respiratory phase, we construct the nonrigid SENSE operator, reformulating the nonrigid motion-corrected reconstruction as a standard regularized inverse problem. In a preliminary study, the proposed method enhanced sharpness of the coronary arteries and improved image quality in non-cardiac regions, outperforming translational motion-corrected reconstruction.