Quantification of three-dimensional (3D) refractive index (RI) with sub-cellular resolution is achieved by digital holographic microtomography (DHμT) using quantitative phase images measured at multiple illumination angles. The DHμT system achieves sensitive and fast phase measurements based on iterative phase extraction algorithm and asynchronous phase shifting interferometry without any phase monitoring or active control mechanism. A reconstruction algorithm, optical diffraction tomography with projection on convex sets and total variation minimization, is implemented to substantially reduce the number of angular scattered fields needed for reconstruction without sacrificing the accuracy and quality of the reconstructed 3D RI distribution. Tomogram of a living CA9-22 cell is presented to demonstrate the performance of the method. Further, a statistical analysis of the average RI of the nucleoli, the nucleus excluding the nucleoli and the cytoplasm of twenty CA9-22 cells is performed.

We demonstrate a common-path tomographic diffractive microscopy technique for three-dimensional (3D) refractive-index (RI) imaging of unstained living cells. A diffraction grating is utilized to generate a reference beam that traverses a blank region of the sample in a common-path off-axis interferometry setup. Single-shot phase images captured at multiple illumination angles are used for 3D RI reconstruction based on optical diffraction tomography. The common-path configuration shows lower temporal phase fluctuations and better RI resolution than a Mach-Zehnder configuration. 3D subcellular RI distributions of live HeLa cells are quantified.

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The scattering properties and refractive indices (RI) of tissue are important parameters in tissue optics. These parameters can be determined from quantitative phase images of thin slices of tissue blocks. However, the changes in RI and structure of cells due to fixation and paraffin embedding might result in inaccuracies in the estimation of the scattering properties of tissue. In this study, three-dimensional RI distributions of cells were measured using digital holographic microtomography to obtain total scattering cross sections (TSCS) of the cells based on the first-order Born approximation. We investigated the slight loss of dry mass and drastic shrinkage of cells due to paraformaldehyde fixation and paraffin embedding removal processes. We propose a method to compensate for the correlated changes in volume and RI of cells. The results demonstrate that the TSCS of live cells can be estimated using restored cells. The percentage deviation of the TSCS between restored cells and live cells was only −8%. Spatially resolved RI and scattering coefficients of unprocessed oral epithelium ranged from 1.35 to 1.39 and from 100 to 450 cm−1, respectively, estimated from paraffinembedded oral epithelial tissue after restoration of RI and volume.

Mitigation of bioaerosol emissions from concentrated animal feeding operations (CAFOs) demands knowledge of bioaerosol concentrations feeding into an end-of-pipe air treatment process. The aim of this preliminary study was to measure total endotoxin and (1!3)-b-glucan concentrations at the air exhaust of 18 commercial CAFOs and to examine their variability with animal operation type (swine farrowing, swine gestation, swine weaning, swine finishing, manure belt laying hen, and tom turkey) and season (cold, mild, and hot). The measured airborne concentrations of total endotoxin ranged from 98 to 23,157 endotoxin units (EU)/m 3 , and the airborne concentrations of total (1!3)-b-D-glucan ranged from 2.4 to 537.9 ng/m 3 . Animal operation type in this study had a significant effect on airborne concentrations of total endotoxin and (1!3)-b-D-glucan but no significant effect on their concentrations in total suspended particulate (TSP). Both endotoxin and (1!3)-b-D-glucan attained their highest airborne concentrations in visited tom turkey buildings. Comparatively, season had no significant effect on airborne concentrations of total endotoxin or (1!3)-b-D-glucan. Endotoxin and (1!3)-b-glucan concentrations in TSP dust appeared to increase as the weather became warmer, and this seasonal effect was significant in swine buildings. Elevated indoor temperatures in the hot season were considered to facilitate the growth and propagation of bacteria and fungi, thus leading to higher biocomponent concentrations in TSP.Implications: This study monitored total endotoxin and (1!3)-b-D-glucan concentrations at the air exhaust of 18 commercial animal buildings during multiple seasons. The airborne concentrations of total endotoxin and (1!3)-b-D-glucan differed significantly with animal operation type but showed no significant effect by season. Given that animal buildings in general have the highest ventilation rates in summer, these findings suggest that endotoxin and (1!3)-b-D-glucan may attain their maximum emission rates in summer. It is therefore recommended that particular attention should be paid to further investigating summertime bioaerosol emissions from animal feeding operations and the emissions' impact on neighboring communities.

The progression of epithelial precancers into cancer is accompanied by changes of tissue and cellular structures in the epithelium. Correlations between the structural changes and scattering coefficients of esophageal epithelia were investigated using quantitative phase images and the scattering-phase theorem. An ex vivo study of 14 patients demonstrated that the average scattering coefficient of precancerous epithelia was 37.8% higher than that of normal epithelia from the same patient. The scattering coefficients were highly correlated with morphological features including the cell density and the nuclear-to-cytoplasmic ratio. A high interpatient variability in scattering coefficients was observed and suggests identifying precancerous lesions based on the relative change in scattering coefficients.

The progression of epithelial dysplasia is accompanied by changes of sub-cellular structures which alter light scattering, particularly backscattering, properties of epithelial cells. In this study, we quantified the refractive index (RI) distributions of normal and cancerous epithelial cells of skin and oral cavity using digital holographic microtomography and investigated the backscattering characteristics of the cells using finite-difference time-domain simulations. The results show that cancerous cells present higher average values of nuclear and nucleolar RI and a higher standard deviation of cytoplasmic RI than normal cells. Both the total scattering and backscattering cross-sections of the cancerous cells are significantly higher than those of the normal cells.

Image reconstruction from limited-angle data is an important issue in diffraction tomography. The limitation of angular coverage usually occurs due to the physical constraints in measurement systems. Insufficient information will deteriorate the quality of reconstructed images. In our experimental setup, the angular range of the data scanning is limited. Here, we applied the iterative algorithm of total variation (TV) minimization to reconstruct the three-dimensional distribution of an object's refractive index from measured phase data. TV-minimization is an edge-preserving technique commonly used in image processing. It can smooth away the noisy textures while retaining sharp edges. Despite a full range of illumination is lacking, we have successfully reconstructed the refractive index distribution of objects numerically and experimentally by use of the TV-minimization algorithm.