Imaging microscopic objects, such as biological cells that are often semi-transparent, using conventional intensity-based light microscopy can be difficult due to lack of contrast between the sample and the environment. Quantitative phase microscopy (QPM) is an effective research tool often used to examine spatial and temporal properties of these semi-transparent samples, label-free, by measuring the optical path delays of light passing through the cells. In recent years, quantitative phase spectroscopy (QPS) was developed in our lab by combining QPM with a rapidly tunable broadband source that allowed accurate spectral signature measurements of the cells. Using this novel method, we were able to quantify the mass of hemoglobin by fitting nonlinear spectral features of individual cells in normal RBC (nRBC) and malaria parasite-infected RBC (iRBC) populations. QPS was also implemented to make morphological multiparametric characterization of nRBC and different stages of malaria parasite iRBC groups that allows population identification using machine learning algorithms.
In combination with microfluidics, quantitative phase imaging is used to monitor high throughput flowing cells. Our holographic cytometer provides well-rounded morphological profiles for different cell lines, including physical traits such as optical volume and area. The large volume of cell imaging data collected from the holographic cytometer serves as training data for logistic regression classifiers, demonstrating the device’s potential as a diagnostic tool. Figure from Park et. al. 2021.