Chapters authored
Cytopathology Using High Resolution Digital Holographic Microscopy
We summarize a study involving simultaneous imaging of cervical cells from Pap-smear samples using bright-field and quantitative phase microscopy. The optimization approach to phase reconstruction used in our study enables full diffraction limited performance from single-shot holograms and is thus suitable for reducing cost of a quantitative phase microscope system. Over 48000 cervical cells from patient samples obtained from three clinical sites have been imaged in this study. The clinical sites used different sample preparation methodologies and the subjects represented a range of age groups and geographical diversity. Visual examination of quantitative phase images of cervical cell nuclei show distinct morphological features that we believe have not appeared in the prior literature. A PCA based analysis of numerical parameters derived from the bright-field and quantitative phase images of the cervical cells shows good separation of superficial, intermediate and abnormal cells. The distribution of phase based parameters of normal cells is also shown to be highly overlapping among different patients from the same clinical site, patients across different clinical sites and for two age groups (below and above 30 years), thus suggesting robustness and possibility of standardization of quantitative phase as an imaging modality for cell classification in future clinical usage.
Part of the book: Augmented Reality and Its Application
Standardization Techniques for Single-Shot Digital Holographic Microscopy
Digital holographic microscopy (DHM) is a mature technology for quantitative phase imaging. Thousands of articles have been published on this topic over the last couple of decades. Our goal in this article is to emphasize that single-shot holographic microscopy systems offer several practical advantages and in principle capture the full diffraction-limited information of interest. Since phase cannot be measured directly, phase reconstruction is inherently a computational problem. In this context, we describe some traditional algorithmic ideas as well as newer sparse optimization-based methodologies for phase reconstruction from single-shot holograms. Robust operation of a DHM system additionally requires a number of auxiliary algorithms associated with fractional fringe detection, phase unwrapping, detection of focus plane, etc., that will be discussed in some detail. With the data-driven nature of applications of DHM being developed currently, the standardization or benchmarking of algorithmic ideas for DHM systems is important so that same sample imaged by different DHM systems provides the same numerical phase maps. Such uniformity is also key to establishing effective communication between DHM developers and potential users and thereby increasing the reach of the DHM technology.
Part of the book: Holography