Hybrid algorithm based on radial symmetry and weighted least-square ellipse fitting for three-dimensional nanometer particle localization

Abstract

Choosing the localization algorithm in superresolution microscopy is an important factor in determining the resolution in such a modality. The point spread function (PSF) in defocused images has ring structures that can be used to localize the three-dimensional (3-D) position of single particles by calculating the ring center (x and y) and radius (z). As there is no well-developed mathematical model for a defocused PSF, it is difficult to perform a fitting-based algorithm in such images. A particle localization algorithm based on radial symmetry and ellipse fitting is developed to localize the centers and radii of defocused PSFs. Our method can localize the 3-D position of a fluorophore within 20-nm precision in three-dimensions in a range of 40 mu m in z-dimension from defocused two-dimensional (2-D) images. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)