Transport of intensity diffraction tomography with non-interferometric synthetic aperture for three-dimensional label-free microscopy.

We present a new label-free three-dimensional (3D) microscopy technique, termed transport of intensity diffraction tomography with non-interferometric synthetic aperture (TIDT-NSA). Without resorting to interferometric detection, TIDT-NSA retrieves the 3D refractive index (RI) distribution of biological specimens from 3D intensity-only measurements at various illumination angles, allowing incoherent-diffraction-limited quantitative 3D phase-contrast imaging. The unique combination of z-scanning the sample with illumination angle diversity in TIDT-NSA provides strong defocus phase contrast and better optical sectioning capabilities suitable for high-resolution tomography of thick biological samples. Based on an off-the-shelf bright-field microscope with a programmable light-emitting-diode (LED) illumination source, TIDT-NSA achieves an imaging resolution of 206 nm laterally and 520 nm axially with a high-NA oil immersion objective. We validate the 3D RI tomographic imaging performance on various unlabeled fixed and live samples, including human breast cancer cell lines MCF-7, human hepatocyte carcinoma cell lines HepG2, mouse macrophage cell lines RAW 264.7, Caenorhabditis elegans (C. elegans), and live Henrietta Lacks (HeLa) cells. These results establish TIDT-NSA as a new non-interferometric approach to optical diffraction tomography and 3D label-free microscopy, permitting quantitative characterization of cell morphology and time-dependent subcellular changes for widespread biological and medical applications.

In Situ Fabrication of Cs3Cu2I5: Tl Nanocrystal Films for High-Resolution and Ultrastable X-ray Imaging.

Cs3Cu2I5 nanocrystals (NCs) are considered to be promising materials due to their high photoluminescence efficiency and X-ray hardness. However, the present strategy depends on tedious fabrication with excessive chemical waste. The evasive iodide ion dissociation, inadaptable ligand system, low stability, and relatively low light yield severely impede their applications. Herein, we develop an in situ fabrication strategy for a flexible and large-area Tl-doped Cs3Cu2I5 NC-polymer composite scintillation film with a high light yield (∼48800 photons/MeV) and improved stability. Tween 80 and phosphinic acid successfully inhibit the oxidation of iodide ions, and the films can be stored for at least six months. As a result, a high spatial resolution of 16.3 lp mm-1 and a low detection limit of 305 nGyair s-1 were achieved. A radioluminescence intensity of >80% was maintained after a total irradiation dose of 604.8 Gy. These results indicate the promising application of these copper halide NCs in low-cost, flexible, and high-performance medical imaging.

Single-shot lensfree on-chip quantitative phase microscopy with partially coherent LED illumination.

We propose a single-shot lens-free phase retrieval (SSLFPR) method in a lens-free on-chip microscopy (LFOCM) system based on a partially coherent light emitting diode (LED) illumination. The finite bandwidth (∼23.95 nm) of LED illumination is divided into a series of quasi-monochromatic components according to the LED spectrum measured by a spectrometer. When the "virtual wavelength scanning" phase retrieval method is combined with the dynamic phase support constraint, the resolution loss caused by the spatiotemporal partial coherence of the light source can be effectively compensated. At the same time, the nonlinearity characteristics of the support constraint help to further improve the imaging resolution, accelerate the convergence of the iteration process, and greatly eliminate the artifacts. Based on the proposed SSLFPR method, we demonstrate that the phase information of samples (including phase resolution target and polystyrene microspheres) illuminated by a LED can be accurately retrieved based on one single diffraction pattern. The SSLFPR method has a half-width resolution of 977 nm across a large field-of-view (FOV) of 19.53 mm2, which is 1.41 × the resolution of the conventional approach. We also imaged living Henrietta Lacks (HeLa) cells cultured in vitro, further demonstrating the real-time single-shot quantitative phase imaging (QPI) capability of SSLFPR for dynamic samples. Given its simple hardware, high throughput, and single-frame high-resolution QPI capability, SSLFPR is expected to be adopted in a wide range of biological and medical applications.

Accurate quantitative phase imaging by the transport of intensity equation: a mixed-transfer-function approach: erratum.

In this erratum, we correct Fig. 4 of our Letter [Opt. Lett.46, 1740 (2021)OPLEDP0146-959210.1364/OL.422095]. This does not change the scientific conclusions of the original Letter.

Accurate quantitative phase imaging by the transport of intensity equation: a mixed-transfer-function approach.

As a well-established deterministic phase retrieval approach, the transport of intensity equation (TIE) is able to recover the quantitative phase of a sample under coherent or partially coherent illumination with its through-focus intensity measurements. Nevertheless, the inherent paraxial approximation limits its validity to low-numerical-aperture imaging and slowly varying objects, precluding its application to high-resolution quantitative phase imaging (QPI). Alternatively, QPI can be achieved by phase deconvolution approaches based on the coherent contrast transfer function or partially coherent weak object transfer function (WOTF) without invoking paraxial approximation. But these methods are generally appropriate for "weakly scattering" samples in which the total phase delay induced by the object should be small. Consequently, high-resolution high-accuracy QPI of "nonweak" phase objects with fine details and large phase excursions remains a great challenge. In this Letter, we propose a mixed-transfer-function (MTF) approach to address the dilemma between measurement accuracy and imaging resolution. By effectively merging the phases reconstructed by TIE and WOTF in the frequency domain, the high-accuracy low-frequency phase "global" profile can be secured, and high-resolution high-frequency features can be well preserved simultaneously. Simulations and experimental results on a microlens array and unstained biological cells demonstrate the effectiveness of MTF.

Wavelength-scanning lensfree on-chip microscopy for wide-field pixel-super-resolved quantitative phase imaging.

We propose a lensfree on-chip microscopy approach for wide-field quantitative phase imaging (QPI) based on wavelength scanning. Unlike previous methods, we found that a relatively large-range wavelength diversity not only provides information to overcome spatial aliasing of the image sensor but also creates sufficient diffraction variations that can be used to achieve motion-free, pixel-super-resolved phase recovery. Based on an iterative phase retrieval and pixel-super-resolution technique, the proposed wavelength-scanning approach uses only eight undersampled holograms to achieve a half-pitch lateral resolution of 691 nm across a large field-of-view of 29.85mm2, surpassing 2.41 times the theoretical Nyquist-Shannon sampling resolution limit imposed by the pixel size of the sensor (1.67 µm). We confirmed the effectiveness of this technique in QPI and resolution enhancement by measuring the benchmark quantitative phase microscopy target. We also showed that this method can track HeLa cell growth within an incubator, revealing cellular morphologies and subcellular dynamics of a large cell population over an extended period of time.

[Spatial and Temporal Distribution Characteristics and the Retention Effects of Nutrients in Xiangjiaba Reservoir].

After the construction of the Xiangjiaba Dam, the hydrodynamic conditions, nutrient distributions, and transport conditions of the Jinsha River were changed. Here, the nutrient distribution characteristics and retention effects of Xiangjiaba Reservoir were investigated according to the results of water quality monitoring from 2015 to 2016. Spatial and temporal variations in TN, TP, SiO32-Si, and other nutrients, and retention flux and retention rate were analyzed. The results showed that the nutrient mass concentration of TN, TP, and SiO32--Si was 0.905 mg·L-1, 0.034 mg·L-1, and 7.98 mg·L-1, respectively. The distribution of TN was affected by point sources and the concentration of TN was large in urban areas. This distribution of TP was mainly granular and the mass concentrations decreased along the river path. The mass concentration of SiO32--Si did not significantly vary over time and space. Furthermore, Xiangjiaba Reservoir had a persistent effect on nutrient salts; the average annual retention of TN, TP, and SiO32--Si was 2.30×104 t·a-1, 0.146×104 t·a-1, and -2.4×104 t·a-1, respectively. During different seasons, the retention of TN and SiO32--Si varied between positive or negative; however, TP appeared to be consistent. The average monthly retention efficiency of TN, TP, and SiO32--Si was 17.5%, 32.8%, and -2.14%, respectively. Overall, retention efficiencies were higher during the dry season than that wet season, and phosphorus retention was most pronounced. The retention of TN in the reservoir may be related to denitrification and the input of external load; the flux of SiO32--Si was mainly affected by runoff; and the particle morphology of phosphorus, as well as reservoir period, were the main factors affecting TP retention. There were no clear correlations between nutrient retention and the mass concentrations of TN and SiO32--Si, but the nutrient retention effect of Xiangjiaba Reservoir reduced TP concentrations along the river path and increased TP concentration with vertical depth.

[Characteristics of Nitrogen Release at the Sediment-Water Interface in the Typical Tributaries of the Three Gorges Reservoir During the Sensitive Period in Spring].

Overlying water and sediment interstitial water samples were acquired to study the nitrogen release between sediments and water interfaces in Xiangxi Bay in April 2016 during the Sensitive Period in spring. The spatial distribution of different forms of nitrogen in the sediment was analyzed, the diffusion fluxes of different forms of nitrogen in the sediments and water systems were also measured, and a correlation analysis with environmental factors was conducted. The results show that overlying water and sediment interstitial water ρ(TN) ranges from 1.10 to 6.90 mg·L-1 and 6.19 to 32.57 mg·L-1 respectively; indicating the nitrogen concentrations in the overlying and interstitial water of sediments have a certain variation along the process and vertically. The interstitial water nitrogen concentrations in the upstream area are higher than those in the downstream area. The interstitial water ρ(NH4+-N) in the sediment is significantly larger than that in the overlying water, but the interstitial water ρ(NO3--N) in the sediment is slightly smaller than that in the overlying water. Xiangxi Bay sediment acts as a source of NH4+-N; however, for NO3--N it is a sink. The diffusive fluxes of NH4+-N range from 2.70 to 4.72 mg·(m2·d)-1; and the diffusive fluxes of NO3--N range from -1.61 to -0.62 mg·(m2·d)-1. Nitrogen is mainly present in the form of ammonium nitrogen in the sediment of Xiangxi Bay. The ρ(NH4+-N) in the sediment ranges from 69.97-1185.97 mg·kg-1, ρ(NO3--N) ranges from 2.78-38.17 mg·kg-1, and the ρ(NH4+-N) in sediments in the surface at 0-8 cm changes with the same trend.

Efficient quantitative phase microscopy using programmable annular LED illumination.

In this work, we present an efficient quantitative phase imaging (QPI) approach using programmable annular LED illumination. As a new type of coded light source, the LED array provides flexible illumination control for noninterferometric QPI based on a traditional microscopic configurations. The proposed method modulates the transfer function of system by changing the LED illumination pattern, which provides noise-robust response of transfer function and achieves twice resolution limit of objective NA. The quantitative phase can be recovered from slightly defocused intensity images through inversion of transfer function. Moreover, the weak object transfer function (WOTF) of axis-symmetric oblique source is derived, and the noise-free and noisy simulation results validate the predicted theory. Finally, we experimentally confirm accurate and repeatable performance of our method by imaging calibrated phase samples and cellular specimens with different NA objectives.

Extent of agreement between the body fluid model of Sysmex XN-20 and the manual microscopy method.

BACKGROUND: Although the correlations concerning cellular component analysis between the Sysmex XN-20 body fluid (BF) model and manual microscopy have been investigated by several studies, the extent of agreement between these two methods has not been investigated. METHODS: A total of 90 BF samples were prospectively collected and analyzed using the Sysmex XN-20 BF model and microscopy. The extent of agreement between these two methods was evaluated using the Bland-Altman approach. Receiver operating characteristic (ROC) curve analysis was employed to evaluate the diagnostic accuracy of high-fluorescence (HF) BF cells for malignant diseases. RESULTS: The agreements of white blood cell (WBC), red blood cell (RBC), and percentages of neutrophils, lymphocytes, and monocytes between the Sysmex XN-20 BF model and manual microscopy were imperfect. The areas under the ROC curves for absolute and relative HF cells were 0.67 (95% confidence interval [CI]: 0.56-0.78) and 0.60 (95% CI: 0.48-0.72), respectively. CONCLUSION: Due to the Sysmex XN-20 BF model's imperfect agreement with manual microscopy and its weak diagnostic accuracy for malignant diseases, the current evidence does not support replacing manual microscopy with this model in clinical practice.