Polarization sensitivity error analysis and measurement of a greenhouse gas monitoring instrument.

Greenhouse gas monitoring instruments (GMI) are spatial heterodyne spectroscopy (SHS) sensors that monitor greenhouse gases (GHG) from space. Due to several kinds of polarization-sensitive optical elements in GMIs, to some extent, the instrument becomes a polarization-sensitive sensor. Its polarization sensitivity will reduce the radiometric accuracy and spectral inversion accuracy of GHG column concentration. Theoretical radiation response models for analyzing the polarization sensitivity of a GMI, which is mainly affected by a scanning mirror beam splitter and diffraction gratings, are presented in this paper. Based on these models and the polarization performance testing, the theoretical and experimental results of the main spectral band of a GMI, covering the wavelength range of 1.568-1.583 µm for carbon dioxide (CO2) detection, have been given. The result shows that the linear polarization sensitivity is less than 0.65% and 1.32% in the nadir (45°, 0°) and in the oblique view direction (45±20°, ±31°), respectively, and that it meets the qualification requirement for an absolute radiometric calibration accuracy better than 5%. The absolute radiometric calibration accuracy directly affects the accuracy of GHG concentration retrieval.

Magnetic and fluorescent Gd2O3:Yb3+/Ln3+ nanoparticles for simultaneous upconversion luminescence/MR dual modal imaging and NIR-induced photodynamic therapy.

The development of upconversion nanoparticles (UCNs) for theranostics application is a new strategy toward the accurate diagnosis and efficient treatment of cancer. Here, magnetic and fluorescent lanthanide-doped gadolinium oxide (Gd2O3) UCNs with bright upconversion luminescence (UCL) and high longitudinal relaxivity (r1) are used for simultaneous magnetic resonance imaging (MRI)/UCL dual-modal imaging and photodynamic therapy (PDT). In vitro and in vivo MRI studies show that these products can serve as good MRI contrast agents. The bright upconversion luminescence of the products allows their use as fluorescence nanoprobes for live cells imaging. We also utilized the luminescence-emission capability of the UCNs for the activation of a photosensitizer to achieve significant PDT results. To the best of our knowledge, this study is the first use of lanthanide-doped Gd2O3 UCNs in a theranostics application. This investigation provides a useful platform for the development of Gd2O3-based UCNs for clinical diagnosis, treatment, and imaging-guided therapy of cancer.

A computer-aided diagnosis system for dynamic contrast-enhanced MR images based on level set segmentation and ReliefF feature selection.

This study established a fully automated computer-aided diagnosis (CAD) system for the classification of malignant and benign masses via breast magnetic resonance imaging (BMRI). A breast segmentation method consisting of a preprocessing step to identify the air-breast interfacing boundary and curve fitting for chest wall line (CWL) segmentation was included in the proposed CAD system. The Chan-Vese (CV) model level set (LS) segmentation method was adopted to segment breast mass and demonstrated sufficiently good segmentation performance. The support vector machine (SVM) classifier with ReliefF feature selection was used to merge the extracted morphological and texture features into a classification score. The accuracy, sensitivity, and specificity measurements for the leave-half-case-out resampling method were 92.3%, 98.2%, and 76.2%, respectively. For the leave-one-case-out resampling method, the measurements were 90.0%, 98.7%, and 73.8%, respectively.

Toxicity evaluation of Gd2O3@SiO2 nanoparticles prepared by laser ablation in liquid as MRI contrast agents in vivo.

Poor toxicity characterization is one obstacle to the clinical deployment of Gd2O3@ SiO2 core-shell nanoparticles (Gd-NPs) for use as magnetic resonance (MR) imaging contrast agents. To date, there is no systematic toxicity data available for Gd-NPs prepared by laser ablation in liquid. In this article, we systematically studied the Gd-NPs' cytotoxicity, apoptosis in vitro, immunotoxicity, blood circulation half-life, biodistribution and excretion in vivo, as well as pharmacodynamics. The results show the toxicity, and in vivo MR data show that these NPs are a good contrast agent for preclinical applications. No significant differences were found in cell viability, apoptosis, and immunotoxicity between our Gd-NPs and Gd in a DTPA (diethylenetriaminepentaacetic acid) chelator. Biodistribution data reveal a greater accumulation of the Gd-NPs in the liver, spleen, lung, and tumor than in the kidney, heart, and brain. Approximately 50% of the Gd is excreted via the hepatobiliary system within 4 weeks. Furthermore, dynamic contrast-enhanced T1-weighted MR images of xenografted murine tumors were obtained after intravenous administration of the Gd-NPs. Collectively, the single step preparation of Gd-NPs by laser ablation in liquid produces particles with satisfactory cytotoxicity, minimal immunotoxicity, and efficient MR contrast. This may lead to their utility as molecular imaging contrast agents in MR imaging for cancer diagnosis.

Ligand-free gadolinium oxide for in vivo T1-weighted magnetic resonance imaging.

Gadolinium oxide (Gd2O3), which can be used as a T1-weighted magnetic resonance imaging (MRI) contrast agent, has attracted intense attention in recent years. In this paper, ligand-free monoclinic Gd2O3 nanocrystals of 7.1 nm in diameter are synthesized by a simple and green approach, namely microsecond laser ablation of a gadolinium (Gd) target in deionized water. These nanocrystals obtain high r1 relaxivity of 5.53 s(-1) mM(-1), and their low toxicity was demonstrated by the cell viability of S18 cells and apoptosis in RAW264.7 cells. In vitro and in vivo MR images show these particles to be good T1-weighted MRI contrast agents. Base on the experimental results and theoretical analysis, we suggest that the purity of the Gd2O3 contributes to its high r1 relaxivity value, while the low toxicity is due to its good crystallinity. These findings show that laser ablation in liquid (LAL) is a promising strategy to synthesize ligand-free monoclinic Gd2O3 nanocrystals for use as high efficient T1-weighted MRI contrast agents.

Structure and haemocompatibility of ZnO films deposited by radio frequency sputtering.

ZnO films were first deposited on silicon and glass substrates using radio frequency sputtering and then annealed in air at different temperatures from 300 to 700 degrees C. The microstructures, surface energy and optical properties of ZnO films were examined by x-ray diffraction, Raman spectroscopy, contact angle test and UV-visible optical absorption spectroscopy, respectively. Results show that a perfectly oriented ZnO (0 0 2) thin film is obtained in all ZnO samples. Raman spectroscopy, in combination with those derived by UV-visible optical absorption spectroscopy, provides us with an accurate description of ZnO nature, revealing that, after annealing, ZnO films exhibit better crystallinity and narrower optical energy gap. The contact angle test denotes that the adhesive work and polar component of the surface energy of ZnO films increase steadily with the annealing temperature, which leads to more active interaction between annealed ZnO films and blood plasma. The platelet adhesion experiment shows that there are fewer platelets adhered to the surface of ZnO films compared to the polyurethane (PU) used in clinical application, suggesting ZnO's better compatibility with blood. As the annealing temperature increases, the number of platelets adhered to ZnO films increases correspondingly, which we believe is due to the narrower optical energy gap. Therefore, the appropriate surface properties and the wide optical energy gap of ZnO thin films are believed to be the main factors responsible for the excellent haemocompatibility.