Abstract：
OBJECTIVE: Navigator-based correction of rigid-body motion reconciling high precision with minimal acquisition, minimal calibration and simple, fast processing.
METHODS: A short orbital navigator (2.3 ms) is inserted in a three-dimensional (3D) gradient echo sequence for human head imaging. Head rotation and translation are determined by linear regression based on a complex-valued model built either from three reference navigators or in a reference-less fashion, from the first actual navigator. Optionally, the model is expanded by global phase and field offset. Run-time scan correction on this basis establishes servo control that maintains validity of the linear picture by keeping its expansion point stable in the head frame of reference. The technique is assessed in a phantom and demonstrated by motion-corrected imaging in vivo.
RESULTS: The proposed approach is found to establish stable motion control both with and without reference acquisition. In a phantom, it is shown to accurately detect motion mimicked by rotation of scan geometry as well as change in global B0 . It is demonstrated to converge to accurate motion estimates after perturbation well beyond the linear signal range. In vivo, servo navigation achieved motion detection with precision in the single-digit range of micrometers and millidegrees. Involuntary and intentional motion in the range of several millimeters were successfully corrected, achieving excellent image quality.
CONCLUSIONS: The combination of linear regression and feedback control enables prospective motion correction for head imaging with high precision and accuracy, short navigator readouts, fast run-time computation, and minimal demand for reference data.
METHODS: A short orbital navigator (2.3 ms) is inserted in a three-dimensional (3D) gradient echo sequence for human head imaging. Head rotation and translation are determined by linear regression based on a complex-valued model built either from three reference navigators or in a reference-less fashion, from the first actual navigator. Optionally, the model is expanded by global phase and field offset. Run-time scan correction on this basis establishes servo control that maintains validity of the linear picture by keeping its expansion point stable in the head frame of reference. The technique is assessed in a phantom and demonstrated by motion-corrected imaging in vivo.
RESULTS: The proposed approach is found to establish stable motion control both with and without reference acquisition. In a phantom, it is shown to accurately detect motion mimicked by rotation of scan geometry as well as change in global B0 . It is demonstrated to converge to accurate motion estimates after perturbation well beyond the linear signal range. In vivo, servo navigation achieved motion detection with precision in the single-digit range of micrometers and millidegrees. Involuntary and intentional motion in the range of several millimeters were successfully corrected, achieving excellent image quality.
CONCLUSIONS: The combination of linear regression and feedback control enables prospective motion correction for head imaging with high precision and accuracy, short navigator readouts, fast run-time computation, and minimal demand for reference data.
摘要：
目的：基于Navigator的刚体运动校正，以最少的采集来协调高精度，最小的校准和简单，快速处理。
方法：将短轨道导航器（2.3ms）插入三维（3D）梯度回波序列中，用于人体头部成像。头部旋转和平移由线性回归确定，该回归基于从三个参考导航器或以无参考方式构建的复值模型。从第一个实际的导航员。可选地,通过全局相位和场偏移扩展模型。在此基础上的运行时间扫描校正建立了伺服控制,该伺服控制通过保持线性图像的扩展点在头部参考系中稳定来保持线性图像的有效性。该技术在体模中进行评估，并通过体内运动校正成像进行演示。
结果：发现所提出的方法可以在有和没有参考采集的情况下建立稳定的运动控制。在幻影中，它显示出准确地检测由扫描几何形状的旋转以及全局B0的变化所模仿的运动。已证明，在扰动远远超出线性信号范围后，可以收敛到准确的运动估计。在体内,伺服导航实现了在微米和毫度的一位数范围内精度的运动检测。成功纠正了几毫米范围内的非自愿和故意运动，实现卓越的图像质量。
结论：线性回归和反馈控制的结合使头部成像具有高精度和准确性的前瞻性运动校正，简短的导航读数，快速运行时计算，对参考数据的需求最小。
方法：将短轨道导航器（2.3ms）插入三维（3D）梯度回波序列中，用于人体头部成像。头部旋转和平移由线性回归确定，该回归基于从三个参考导航器或以无参考方式构建的复值模型。从第一个实际的导航员。可选地,通过全局相位和场偏移扩展模型。在此基础上的运行时间扫描校正建立了伺服控制,该伺服控制通过保持线性图像的扩展点在头部参考系中稳定来保持线性图像的有效性。该技术在体模中进行评估，并通过体内运动校正成像进行演示。
结果：发现所提出的方法可以在有和没有参考采集的情况下建立稳定的运动控制。在幻影中，它显示出准确地检测由扫描几何形状的旋转以及全局B0的变化所模仿的运动。已证明，在扰动远远超出线性信号范围后，可以收敛到准确的运动估计。在体内,伺服导航实现了在微米和毫度的一位数范围内精度的运动检测。成功纠正了几毫米范围内的非自愿和故意运动，实现卓越的图像质量。
结论：线性回归和反馈控制的结合使头部成像具有高精度和准确性的前瞻性运动校正，简短的导航读数，快速运行时计算，对参考数据的需求最小。
