arXiv:2507.14924cs.CV2025-07

提出新方法提升低温电镜三维重构精度,解决低信噪比下的姿态与偏移误差问题。

3-Dimensional CryoEM Pose Estimation and Shift Correction Pipeline

  • 基于多维缩放和共线几何,用鲁棒优化估计粒子旋转轴与平面向量
  • 在低信噪比下相比传统方法提升欧拉角精度与三维重建保真度
  • 适合从事低温电镜图像处理、结构生物学研究者参考

由于低温电镜投影图像信噪比极低,准确的姿态估计与偏移校正成为关键挑战,直接影响三维重构质量。本文提出一种基于多维缩放(MDS)技术的冷冻电镜姿态估计方法,通过二面角对估计每个粒子的3D旋转矩阵,将旋转矩阵表示为旋转轴与垂直于轴的单位向量。该方法利用3D重构中的共线概念,但因低信噪比导致共线估计误差大。为此,引入两个互补模块:(i) 基于ℓ₁范数的联合优化框架,通过投影坐标下降法精确满足单位长度与正交性约束,同时估计旋转轴与平面向量;(ii) 迭代式偏移校正算法,通过全局最小二乘法估计一致的平面平移。相较以往依赖ℓ₂目标函数且近似满足几何约束的方法,本方案避免误差累积,在傅里叶壳相关(FSC)指标上持续优于先前方法,显著提升低信噪比条件下的重建精度。

原文摘要 · Abstract (English)

Accurate pose estimation and shift correction are key challenges in cryo-EM due to the very low SNR, which directly impacts the fidelity of 3D reconstructions. We present an approach for pose estimation in cryo-EM that leverages multi-dimensional scaling (MDS) techniques in a robust manner to estimate the 3D rotation matrix of each particle from pairs of dihedral angles. We express the rotation matrix in the form of an axis of rotation and a unit vector in the plane perpendicular to the axis. The technique leverages the concept of common lines in 3D reconstruction from projections. However, common line estimation is ridden with large errors due to the very low SNR of cryo-EM projection images. To address this challenge, we introduce two complementary components: (i) a robust joint optimization framework for pose estimation based on an $\ell_1$-norm objective or a similar robust norm, which simultaneously estimates rotation axes and in-plane vectors while exactly enforcing unit norm and orthogonality constraints via projected coordinate descent; and (ii) an iterative shift correction algorithm that estimates consistent in-plane translations through a global least-squares formulation. While prior approaches have leveraged such embeddings and common-line geometry for orientation recovery, existing formulations typically rely on $\ell_2$-based objectives that are sensitive to noise, and enforce geometric constraints only approximately. These choices, combined with a sequential pipeline structure, can lead to compounding errors and suboptimal reconstructions in low-SNR regimes. Our pipeline consistently outperforms prior methods in both Euler angle accuracy and reconstruction fidelity, as measured by the Fourier Shell Correlation (FSC).

低温电镜姿态估计三维重构图像处理

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