Segmentation of Heterochromatin Foci Using a 3D Spherical Harmonics Intensity Model

We introduce a 3D model-based approach for automatic segmentation of 3D fluorescent heterochromatin foci from 3D microscopy images. The approach employs a new 3D parametric intensity model based on a spherical harmonics (SH) expansion and can represent foci of regular and highly irregular shapes. By solving a least-squares optimization problem, the model is directly fitted to the 3D image data, and the model parameters including the SH expansion coefficients are estimated. The approach has been successfully applied to real 3D microscopy image data. A visual comparison and a quantitative evaluation show that the new approach yields better results than previous approaches.