IEEE Trans Med Imaging. 2023 Sep;42(9):2706-2713. doi: 10.1109/TMI.2023.3263167. Epub 2023 Aug 31.
The advent of optically pumped magnetometers (OPMs) facilitates the development of on-scalp magnetoencephalography (MEG). In particular, the triaxial OPM emerged recently, making simultaneous measurements of all three orthogonal components of vector fields possible. The detection of triaxial magnetic fields improves the interference suppression capability and achieves higher source localization accuracy using fewer sensors. The source localization accuracy of MEG is based on the accurate co-registration of MEG and MRI. In this study, we proposed a triaxial co-registration method according to combined principal component analysis and iterative closest point algorithms for use of a flexible cap. A reference phantom with known sensor positions and orientations was designed and constructed to evaluate the accuracy of the proposed method. Experiments showed that the average co-registered position errors of all sensors were approximately 1 mm and average orientation errors were less than 2.5° in the X -and Y orientations and less than 1.6° in the Z orientation. Furthermore, we assessed the influence of co-registration errors on the source localization using simulations. The average source localization error of approximately 1 mm reflects the effectiveness of the co-registration method. The proposed co-registration method facilitates future applications of triaxial sensors on flexible caps.
光泵磁强计（OPM）的出现促进了头皮磁图仪（MEG）的发展。特别是三轴 OPM 的出现，使得对矢量场的所有三个正交分量进行同时测量成为可能。三轴磁场的检测提高了干扰抑制能力，并通过使用更少的传感器实现了更高的源定位精度。MEG 的源定位精度基于 MEG 和 MRI 的精确配准。在这项研究中，我们提出了一种基于组合主成分分析和迭代最近点算法的三轴配准方法，用于柔性帽。设计并构建了一个具有已知传感器位置和方向的参考体模，以评估所提出方法的准确性。实验表明，所有传感器的平均配准位置误差约为 1 毫米，在 X 和 Y 方向的平均方向误差小于 2.5°，在 Z 方向的平均方向误差小于 1.6°。此外，我们还通过模拟评估了配准误差对源定位的影响。平均约 1 毫米的源定位误差反映了配准方法的有效性。所提出的配准方法有助于未来在柔性帽上使用三轴传感器。
