SFB Tomography across the scales: Optical Tomography of Trapped Objects

Optical and acoustical trapping has been established as a tool for holding and moving microscopic particles suspended in a liquid in a contact-free and non-invasive manner. Opposed to standard microscopic imaging where the probe is fixated, this technique allows imaging in a more natural environment.

In collaboration with the the Division for Biomedical Physics at the University of Innsbruck we aim to develop optical tomography techniques that deliver valuable quantitative information, useful for instance in the context of monitoring the development of cells in organoids, embryos, or tumors.

The major challenge in the given setting is that, in contrast to classical computerized tomography, the motion of the particle in the trap is irregular and has to be estimated in addition to the inner structure of the object. A main ingredient for our reconstruction of the motion is the common line method known for the determination of the relative orientations of different projection images as it is used, for example, in cryogenic electron microscopy. An infinitesimal version of this common line technique, allows us (after correcting for a potential translation by tracking the center of the images) to find at every time step the local angular velocity of the motion from an infinitesimally short observation time.

We have already obtained good results for simulated data and in the future, our motion estimation method will be tested on video data acquired from biological samples.

Image caption: Video frames from a video recorded of a pollen grain (Sansevieria trifasciata) rotating in an acoustic trap. Image Courtesy: Mia Kvåle Løvmo and Benedikt Pressl
Text by Denise Schmutz