  There is an increasing need for label free methods that could reveal
intracellular structures and dynamics. In this context, we develop a new
optical tomography method working in transmission - Full-field optical
transmission tomography (FF-OTT). The method can measure the forward scattering
signals and reveal the metabolic time-dependent signals in living cells. FF-OTT
is a common path interferometer taking advantage of the Gouy phase shift - a
{\pi} phase shift that the light wave experiences around the focus. By
modulating position of the focus one can alter the phase of the scattered
light. Demodulation of images with different phases rejects the background and
enhances the light from the depth-of-focus, thus producing an optical section.
We test FF-OTT by imaging single-cell diatoms and ex vivo biological samples.
In fresh samples, we show that the intracellular motions create visible
intensity fluctuations in FF-OTT so that the method is able to reveal a
metabolic dynamic contrast. FF-OTT was found to be an efficient label free
technique that can be readily implemented thanks to a robust common-path
speckle-free interferometer design using an incoherent light source.
