Low‐dose X‐ray computed tomography ( LDCT ) imaging is highly recommended for use in the clinic because of growing concerns over excessive radiation exposure. However, the CT images reconstructed by the conventional filtered back‐projection ( FBP ) method from low‐dose acquisitions may be severely degraded with noise and streak artifacts due to excessive X‐ray quantum noise, or with view‐aliasing artifacts due to insufficient angular sampling. In 2005, the nonlocal means ( NLM ) algorithm was introduced as a non‐iterative edge‐preserving filter to denoise natural images corrupted by additive Gaussian noise, and showed superior performance. It has since been adapted and applied to many other image types and various inverse problems. This paper specifically reviews the applications of the NLM algorithm in LDCT image processing and reconstruction, and explicitly demonstrates its improving effects on the reconstructed CT image quality from low‐dose acquisitions. The effectiveness of these applications on LDCT and their relative performance are described in detail.
Advanced oxidation protein products (AOPPs) as a novel marker of oxidative stress, are involved in a variety of diseases, including osteoporosis. Although a number of studies have shown the possible functions of AOPPs in biological processes, little is known about the role of AOPPs in the pathogenesis of osteoporosis. In this study, we aimed to investigate the effect of AOPPs on the proliferation and osteogenic differentiation of rat mesenchymal stem cells (MSCs). MSCs, isolated from bone marrow, were cultured in the absence or presence of AOPPs (50, 100, 200 and 400 mg/ml). MTT assay was used to determine the proliferative ability of the cells. Alkaline phosphatase (ALP) activity, the mRNA expression of ALP and collagen I and bone nodule formation were detected to assess osteogenic differentiation. Reactive oxygen species (ROS) generation was analyzed with the probe 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA). The expression of receptor of advanced glycation end-products (RAGE) at the mRNA and protein level was detected by real-time PCR and western blot analysis, respectively. Compared with the control group, AOPPs inhibited MSC proliferation in a dose- and time-dependent manner. Moreover, AOPPs induced a significant reduction in ALP activity, as well as a decrease in ALP and collagen I mRNA levels in the MSCs; bone nodule formation was also inhibited. Furthermore, AOPPs increased ROS generation in the MSCs, and upregulated the expression of RAGE at the mRNA and protein level. These results suggest that AOPPs inhibit the proliferation and osteogenic differentiation of MSCs, possibly through the AOPPs-RAGE-ROS pathway; this may be an important mechanism in the development of osteoporosis.
This work was to devise a comprehensive testing scheme to evaluate the geometric and dosimetric accuracy of the Edge accelerator gating with electromagnetic tracking (EMT) for its safety in clinical application. A CIRS thorax phantom was scanned with four-dimensional cone-beam CT (4D-CBCT) on an Edge accelerator while the simulated tumor was simultaneously tracked with an EMT system using Calypso. The geometric accuracy was validated by comparing the motion trajectories derived from Calypso and 4D-CBCT with the ground truth from motion control software. The two-dimensional and three-dimensional dynamic doses were measured with the Matrixx and ArcCHECK installed on a motion platform, both with and without EMT. For tumor motion with 5, 7.5 mm amplitudes, the average absolute differences of sample position between Calypso and the ground truth were 0.286±0.234 mm, 0.407±0.331 mm respectively. Dosimetric accuracy was validated with 3 mm/3% gamma criterion. The average gamma pass rates of 2D dynamic dose validation based on Matrixx were less than 46% without EMT, 97.3% using 2 mm gating limit, 96% using 3 mm gating limit and 93.4% using 5mm gating limit respectively. The mean 3D dynamic dose validation pass rates based on ArcCHECK were 65.9% without EMT, 96.2% using 3 mm gating limit, and 92.5% using 5 mm gating limit with EMT respectively. The geometric accuracy of the Calypso system in tracking the moving target area was stable at the submillimeter level. The dosimetric accuracy could be improved significantly with EMT using an appropriate gating limit.
Background: Inflammatory bowel disease (IBD) is a global gastrointestinal disease characterized by relapsing and remitting inflammatory conditions. Flos Puerariae (the flower of Pueraria lobata [Willd.] Ohwi and P. thomsonii Benth.) and Hovenia dulcis Thunb. (Rhamnaceae) are traditional Chinese medicines. This medicinal pair has been used to treat various diseases due to its excellent anti-oxidant and anti-inflammatory activity. However, the effects of extracts from these plants on dextran sulfate sodium (DSS)-induced colitis have not been investigated; further study is needed to improve the understanding of their mechanisms of action and potential applications. Methods: The chemical constitution of extracts from Flos Puerariae and Semen Hoveniae (PHE) was analyzed using UPLC-LTQ-Orbitrap-MS/MS. The protective effects of PHE on mice with DSS-induced colitis were evaluated through assessment of body weight loss, disease activity index (DAI) score, colon length shortening, and pathological changes. The levels of inflammatory cytokines were determined by ELISA and RT-qPCR. Biomarkers of oxidative stress (ROS, CAT, SOD, MDA, and T-AOC) were analyzed using biochemical kits. The expression of MAPK proteins was determined by Western blotting analysis. Gut microbiota were analyzed via 16S rRNA sequencing. Results: Chemical composition analysis indicated that PHE contains various bioactive compounds, including puerarin, kakkalide, tectoridin, and genistin. The findings from this study suggest that PHE could effectively modulate histopathological score, inflammatory cell infiltration, and inflammatory factor secretion. Notably, PHE ameliorated oxidative stress by inhibiting activation of the MAPK pathway, leading to decreased inflammatory mediators and restored antioxidant enzyme activity. Furthermore, PHE treatment regulated the composition of the gut microbiota by increasing the abundance of benign bacteria, such as Akkermansia, and reducing the abundance of harmful bacteria, such as Proteobacteria. Conclusion: The findings from this study demonstrate the mechanism underlying the amelioration of DSS-induced intestinal oxidative stress by PHE and its positive impact on the restoration of the composition of gut microbiota.
Four Dimensional Cone-Beam Computed Tomography (4D-CBCT) imaging is important in upper abdomen tumor radiation treatment as it can obtain the tumor motion information immediately prior to treatment.However, the number of projections at a single phase for 4D-CBCT imaging is very small, and the CT images reconstructed by using conventional algorithms will be contaminated by view aliasing artifacts and noises.In order to address this problem, we propose a framework to jointly estimate and compensate the inter-phase motion for 4D-CBCT image reconstruction.Specifically, by introducing the intensity-based optical flow (OF) constraint into the reconstruction framework, the model can deal with the inter-frame displacements and improve the image quality simultaneously.The primal-dual algorithm method was used to optimize the cost function of the proposed model.Experiments on physical phantoms and patient data show that the proposed approach can effectively reduce the noise and artifacts in 4D-CBCT images and achieve the inter-phase motion vector fields (MVFs).
Secondary bacterial lung infection (SBLI) is a serious complication in patients with H7N9 virus infection, and increases disease severity. The oropharyngeal (OP) microbiome helps prevent colonisation of respiratory pathogens. We aimed to investigate the OP microbiome of H7N9 patients with/without secondary bacterial pneumonia using 16S rRNA gene sequencing. OP swab samples were collected from 51 H7N9 patients (21 with SBLI and 30 without) and 30 matched healthy controls (HCs) and used for comparative composition, diversity and richness analyses of microbial communities. Principal coordinates analysis successfully distinguished between the OP microbiomes of H7N9 patients and healthy subjects, and the OP microbiome diversity of patients with SBLI was significantly increased. There was significant dysbiosis of the OP microbiome in H7N9 patients, with an abundance of Leptotrichia, Oribacterium, Streptococcus, Atopobium, Eubacterium, Solobacterium and Rothia species in patients with SBLI, and Filifactor, Megasphaera and Leptotrichia species in patients without SBLI, when compared with HCs. Importantly, Haemophilus and Bacteroides species were enriched in HCs. These findings revealed dysbiosis of the OP microbiota in H7N9 patients, and identified OP microbial risk indicators of SBLI, suggesting that the OP microbiome could provide novel and non-invasive diagnostic biomarkers for early microbiota-targeted prophylactic therapies for SBLI prevention.
Intestinal flora provides an important contribution to the development of pulmonary tuberculosis (PTB). We performed a cross-sectional study in 52 healthy controls (HCs) and 83 patients with untreated active PTB to assess the differences in their microbiomic and metabolic profiles in faeces via V3-V4 16S rRNA gene sequencing and gas chromatography-mass spectrometry. Patients with PTB had considerable reductions in phylogenetic alpha diversity and the production of short-chain fatty acids, dysbiosis of the intestinal flora and alterations in the faecal metabolomics composition compared with HCs. Significant alterations in faecal metabolites were associated with changes in the relative abundance of specific genera. Our study describes the imbalance of the gut microbiota and altered faecal metabolomics profiles in patients with PTB; the results indicate that the gut microbiota and faecal metabolomic profiles can be used as potential preventive and therapeutic targets for PTB.
Abstract The relationship between gut microbes and COVID-19 or H1N1 flu is not fully understood. Here, we compared gut mycobiota of 67 COVID-19 patients, 35 H1N1 patients and 48 healthy controls (HCs) using internal transcribed spacer (ITS) 3-ITS4 sequencing. Fungal richness decreased in COVID-19 and H1N1 patients compared to HCs, but fungal diversity decreased in only H1N1 patients. Fungal mycobiota dysbiosis in both COVID-19 and H1N1 patients was mainly characterized by depletions of fungi such as Aspergillus , Penicillium , but several fungi, such as Candida parapsilosis , and Malassezia yamatoensis , were enriched in H1N1 patients. The altered fungal taxa were strongly associated with clinical features such as the incidence of diarrhoea, albumin. Gut mycobiota between COVID-19 patients with mild and severity symptoms are not different, as well as between COVID-19 patients in and out hospital. Therefore, gut mycobiota dysbiosis occur in covid-19 or H1N1 patients and do not improve until discharge.
Adiponectin has been proposed to have an essential role in the regulation of insulin sensitivity and metabolism, but previous studies on levels of adiponectin in prediabetes remain inconsistent. The present study aimed to assess the differences of adiponectin levels between prediabetes patients and healthy controls by carrying out a meta-analysis.We carried out a systematic literature search of PubMed, EMBASE, and other databases for case-control studies and cohort studies measuring adiponectin levels in serum or plasma from prediabetes patients and healthy controls. The pooled weighted mean difference (WMD) and 95% confidence interval (CI) were used to estimate the association between adiponectin levels and prediabetes.Three cohort studies and 15 case-control studies with a total of 41,841 participants were included in the meta-analysis. The results showed that circulating adiponectin levels in prediabetes patients were significantly lower than that of healthy controls (WMD -1.694 μg/mL; 95% CI -2.151, -1.237; P < 0.001). Subgroup analysis showed more significant differences between prediabetes patients and healthy controls when the ratio of the homeostatic model assessment of insulin resistance was >2.12 (WMD -2.95 μg/mL; 95% CI -4.103, -1.806; P < 0.001) and average age was >60 years (WMD -2.20 μg/mL; 95% CI -3.207, -1.201; P < 0.001). Additionally, WMD in adiponectin showed a trend of direct correlation in subgroups of homeostatic model assessment of insulin resistance ratio, body mass index and age.The present meta-analysis supports adiponectin levels in prediabetes patients being lower than that of healthy controls,indicating that the level of circulating adiponectin decreases before the onset of diabetes.
Dynamic positron emission tomography (PET) imaging provides important quantitative information of physiological and biochemical processes in humans and animals. However, due to short-time acquisitions to obtain a time sequence of images for parametric imaging, the signal-to-noise ratio of measurement data in each time frame is often very low, which leads the dynamic PET image reconstruction to be a challenging task. And some noticeable errors are inevitable transferred to the voxel-wise kinetic parameter imaging from the associative noisy TAC measurements. To tackle this problem, maximum a posteriori (MAP) statistical reconstruction methods are widely used by incorporating some prior information. Conventional priors focus on local neighborhoods in individual image frames and subsequently penalize inter-voxel intensity differences through different penalty functions such as the quadratic membrane smoothing prior and non-quadratic edge-preserving prior, failing to explore the temporal information of dynamic PET data. In this paper, we design a spatial-temporal edge-preserving (STEP) prior model under the framework of bilateral filter by considering both the spatial local neighborhoods and the temporal kinetic information. Experimental results via a computer simulation study demonstrate that the present dynamic PET reconstruction method with the STEP prior can achieve noticeable gains than the conventional Huber prior in term of signal-to-noise and bias-variance evaluations for the parametric images.
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