The Laboratory of biological electron microscopy and structural biology

(dr. fei sun’s lab)

 
 

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In electron tomography, alignment accuracy is critical for high-resolution reconstruction. However, the automatic alignment of a tilt series without fiducial markers remains a challenge. Here, we propose a new alignment method based on Scale-Invariant Feature Transform (SIFT) for marker-free alignment. The method covers the detection and localization of interest points (features), feature matching, feature tracking and optimization of projection parameters. The proposed method implements a highly reliable matching strategy and tracking model to detect a huge number of feature tracks. Furthermore, an incremental bundle adjustment method is devised to tolerate noise data and ensure the accurate estimation of projection parameters. Our method was evaluated with a number of experimental data, and the results exhibit an improved alignment accuracy comparable with current fiducial marker alignment and subsequent higher resolution of tomography.


Reference:

Han R., Zhang F., Wan X., Fernandez J.J., Sun F. and Liu Z. (2014). A marker-free automatic alignment method based scale-invariant features. Journal of Structural Biology, 186 : 167-180. doi: 10.1016/j.jsb.2014.02.011. (The program AtomAlign can be downloaded from http://ear.ict.ac.cn/)

(In collaboration with Prof. Fa Zhang, Institute of Computation Technology, CAS)

A marker-free automatic alignment method based on scale-invariant features

Comparison of two tomograms reconstructed from the same tilt series but aligned differently. (a) and (c) The alignment made by IMOD using the cross-correlation method. (b) and (d) The alignment made by AtomAlign using the scale-invariant feature. All the tomograms were reconstructed using WBP method in IMOD.