Improved 3D cellular imaging by multispectral focus assessment

Abstract

Biological specimens are three-dimensional structures. However, when capturing their images through a microscope, there is only one plane in the field of view that is in focus, and out-of-focus portions of the specimen affect image quality in the in-focus plane. It is well-established that the microscope's point spread function (PSF) can be used for blur quantitation, for the restoration of real images. However, this is an ill-posed problem, with no unique solution and with high computational complexity. In this work, instead of estimating and using the PSF, we studied focus quantitation in multi-spectral image sets. A gradient map we designed was used to evaluate the sharpness degree of each pixel, in order to identify blurred areas not to be considered. Experiments with realistic multi-spectral Pap smear images showed that measurement of their sharp gradients can provide depth information roughly comparable to human perception (through a microscope), while avoiding PSF estimation. Spectrum and morphometrics-based statistical analysis for abnormal cell detection can then be implemented in an image database where the axial structure has been refined.

Biomedical Applications of Translational Optical Imaging: From Molecules to Humans

“…Given the amount and diversity of the data gathered, we also focused on machine vision and robotics issues [45][46][47], new types of image handling, from better remapping [44] and segmentation to machine learning and AI approaches [47,48], better 3D methods [49] and color/wavelength multiplexing (see Section 2.5 below). All major microscope manufacturers worked with us, and eventually added significant automation to their top-of-the-line instruments, thus adopting multi-mode microscopy.…”