As a result of the shallow depth of focus of the optical imaging system, the use of standard filtered back projection in optical projection tomography causes space-variant tangential blurring that increases with the distance to the rotation axis. We present a novel optical tomographic image reconstruction technique that incorporates the point spread function of the imaging lens in an iterative reconstruction. The technique is demonstrated using numerical simulations, tested on experimental optical projection tomography data of single fluorescent beads, and applied to high-resolution emission optical projection tomography imaging of an entire zebrafish larva. Compared to filtered back projection our results show greatly reduced radial and tangential blurring over the entire [Formula: see text] mm field of view, and a significantly improved signal to noise ratio.

In vivo imaging of small animals is of wide interest to the biomedical community studying biological disease and developmental processes. However, optical imaging deep in tissue is severely limited by light scattering, posing restrictions on the imaging depth, image contrast, and spatial resolution. We demonstrate optical coherence projection tomography (OCPT) as a fast three-dimensional optical imaging technique for ballistic, non-scattered light, deep-tissue imaging. OCPT is based on a novel scanning transmission sample arm to rapidly measure ballistic light projections of amplitude and phase through thick biological tissues. We demonstrate the strength of OCPT by imaging an adult zebrafish in a total volume of 1000 m m 3 acquired in 24 min. We achieve an unprecedented imaging depth of 4 mm in biological tissue without using optical clearing (up to 27 mean free paths of photon transport). A new way of analyzing optical tomographic imaging depth is demonstrated and applied to OCPT. It shows that the strong light scattering suppression in OCPT is pivotal to reach the SNR limited imaging depth. OCPT allows for a full quantitative assessment of tissue parameters, which is demonstrated by quantifying the attenuation coefficient, refractive index, surface area, and volume of various organs deep inside the zebrafish. Our work opens up the way for longitudinal in vivo small animal studies from the larval to the adult stages.

We present a comparison of image reconstruction techniques for optical projection tomography. We compare conventional filtered back projection, sinogram filtering using the frequency-distance relationship (FDR), image deconvolution, and 2D point-spread-function-based iterative reconstruction. The latter three methods aim to remove the spatial blurring in the reconstructed image originating from the limited depth of field caused by the point spread function of the imaging system. The methods are compared based on simulated data, experimental optical projection tomography data of single fluorescent beads, and high-resolution optical projection tomography imaging of an entire zebrafish larva. We demonstrate that the FDR method performs poorly on data acquired with high numerical aperture optical imaging systems. We show that the deconvolution technique performs best on highly sparse data with low signal-to-noise ratio. The point-spread-function-based reconstruction method is superior for nonsparse objects and data of high signal-to-noise ratio.

We present transmission optical coherence tomography (transmission OCT) as a versatile tool to measure optical material properties of turbid media. The transmission OCT signal is described in detail and it is demonstrated how the group refractive index (n(g)), group velocity dispersion (GVD) and optical attenuation can be determined from this signal. We experimentally validate the refractive index properties of glasses, liquids and glucose water solutions in terms of n(g) and GVD. Measurements of scattering coefficients are determined using transmission OCT for suspensions of silica particles. Quantitative agreement is obtained with a dependent scattering model, both for the average as well as the wavenumber resolved optical attenuation coefficient. Good agreement is observed between our measurements and literature values.

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