Haeberlin Maximilian, Kasper Lars, Barmet Christoph, Brunner David O, Dietrich Benjamin E, Gross Simon, Wilm Bertram J, Kozerke Sebastian, Pruessmann Klaas P
Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.
Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.
Magn Reson Med. 2015 Sep;74(3):647-60. doi: 10.1002/mrm.25432. Epub 2014 Sep 12.
Sinusoidal gradient oscillations in the kilohertz range are proposed for position tracking of NMR probes and prospective motion correction for arbitrary imaging sequences without any alteration of sequence timing. The method is combined with concurrent field monitoring to robustly perform image reconstruction in the presence of potential dynamic field deviations.
Benchmarking experiments were done to assess the accuracy and precision of the method and to compare it with theoretical predictions based on the field probe's time-dependent signal-to-noise ratio. An array of four field probes was used to perform real-time prospective motion correction in vivo. Images were reconstructed based on both predetermined and concurrently measured k-space trajectories.
For observation windows of 4.8 ms, the precision of probe position determination was found to be 35 to 62 µm, and the maximal measurement error was 595 µm root-mean-square on a single axis. Sequence update per repetition time on this basis yielded images free of conspicuous artifacts despite substantial head motion. Predetermined and concurrently observed k-space trajectories yielded equivalent image quality.
NMR field probes in conjunction with gradient tones permit the tracking and prospective correction of rigid-body motion. Relying on gradient oscillations in the kilohertz range, the method allows for concurrent motion detection and image encoding.
提出在千赫兹范围内的正弦梯度振荡用于核磁共振（NMR）探头的位置跟踪以及对任意成像序列进行前瞻性运动校正，且无需改变序列定时。该方法与同步场监测相结合，以便在存在潜在动态场偏差的情况下稳健地进行图像重建。
进行了基准实验，以评估该方法的准确性和精确性，并将其与基于场探头随时间变化的信噪比的理论预测进行比较。使用一组四个场探头在体内进行实时前瞻性运动校正。基于预先确定的和同时测量的k空间轨迹重建图像。
对于4.8毫秒的观察窗口，发现探头位置确定的精度为35至62微米，在单轴上最大测量误差为均方根595微米。在此基础上，每个重复时间进行序列更新，尽管头部有大幅运动，仍能生成无明显伪影的图像。预先确定的和同时观察到的k空间轨迹产生了等效的图像质量。
NMR场探头与梯度音相结合可实现刚体运动的跟踪和前瞻性校正。该方法依赖于千赫兹范围内的梯度振荡，允许同时进行运动检测和图像编码。
