Label-free optical methods such as quantitative phase imaging (QPI) can be used to access mechanical properties and changes in (intra-)cellular morphology non-invasively. The measurements provide information about the local thickness and refractive index at high imaging speed. This allows e.g. long-term monitoring of cell dry mass, enabling measurements of cell growth rate and mass transport.
We are using quantitative phase retrieval by Fourier cut-off filtering of a partially coherent white-light trans-illumination image stack. In combination with multiplane imaging, we can acquire 3D QPI data only limited by the camera speed enabling measurements with a vast range of timescales from milliseconds to days.
