Detection method for unrecognized spatial disorientation based on optical flow stimuli.

BACKGROUND: Flight accidents caused by spatial disorientation (SD) greatly affect flight safety. OBJECTIVE: Few studies have been devoted to the evaluation of SD. METHODS: 10 pilots and 10 non-pilots were recruited for the experimental induction of SD. Videos for giving optical flow stimuli were played at two different flow speeds to induce SD. Subjective judgment and center of foot pressure (CoP) data were collected from the tests. The data were combined to determine the occurrence of SD and analyze the SD types. RESULTS: The number of self-reported SD events was slightly smaller in the pilots than in the non-pilots. The average upper bound of the confidence interval for the standard deviation of CoP was 0.32 ± 0.09 cm and 0.38 ± 0.12 cm in the pilots and non-pilots, respectively. This indicator was significantly lower in the pilots than in the non-pilots (P= 0.03). The success rate of the experimental induction of unrecognized SD was 26.7% and 45.0% in the pilots and non-pilots, respectively. CONCLUSION: The method offered a new to analyze unrecognized SD. We could determine the occurrence unrecognized SD. This is an essential means of reducing flight accidents caused by unrecognized SD.

3D directional gradient L0 norm minimization guided limited-view reconstruction in a dual-panel positron emission mammography.

BACKGROUND: Dual-panel PET is often used for local organ imaging, especially breast imaging, due to its simple structure, high sensitivity, good in-plane resolution, and straightforward fusion with other imaging modalities. Nevertheless, because of data loss caused by the dual-panel structure, using conventional image reconstruction methods results in limited-view artifacts and low image quality in dual-panel positron emission mammography (PEM), which may seriously affect the diagnosis. To mitigate the limited-view artifacts in the dual-panel PEM, we propose a 3D directional gradient L0 norm minimization (3D-DL0) guided reconstruction method. METHODS: The detailed derivation and reasonable simplification of the 3D-DL0 algorithm are given first. Using this algorithm, we then obtain a prior image with edge recovery but contrast loss. To limit the solution space, the 3D-DL0 prior is introduced into the Maximum a Posteriori reconstruction. Meanwhile, a space-invariant point spread function is also implemented to restore image contrast and boundaries. Finally, the reconstructed images with limited-view artifact suppression are obtained. The proposed method was evaluated using the data acquired from physical phantoms and patients with breast tumors on a commercial dual-panel PET system. RESULTS: The qualitative and quantitative studies for phantom data and the blind reader study for clinical data show that the proposed method is more effective in reaching a balance between artifact elimination and image contrast improvement compared with various limited-view reconstruction methods. In addition, the iteration process of the method is proved convergent numerically. CONCLUSIONS: The image quality improvement confirms the potential value of the proposed reconstruction algorithm to address the limited-view problem, and thus improve diagnostic accuracy in dual-panel PEM imaging.

DH-Mammo PET: a dual-head positron emission mammography system for breast imaging.

Objective. To develop a simultaneous positron emission tomography-Optical (OPET) breast imaging dual-head PET subsystem, called DH-Mammo PET, for accurate, early diagnosis and efficacy assessment of breast cancer with high resolution and sensitivity.Approach. We developed a breast-dedicated PET based on LYSO crystal, silicon photomultiplier array and multi-voltage threshold sampling technique. It consists of two detector heads, each with a detection area of 216 mm × 145.5 mm. The distance between the detector heads is fixed at 120 mm. In order to extract coincidences and correct data, GPU-based software coincidence processing, random, scatter, normalization, gap-filling and attenuation corrections were applied in turn. The images were reconstructed using maximum likelihood expectation maximization with depth of interaction (DOI) modeling. The performance of DH-Mammo PET was evaluated referring to NEMA NU 4-2008, NU 2-2007 and Chinese industry recommended standard YY/T 1835-2022. Besides, several clinical patient images of DH-Mammo PET were compared with those of a whole-body PET/CT.Main results. The energy resolution was 14.5%, and time resolution was < 1.31 ns. Indicated by the22Na point source imaging, its spatial resolution was 2.60 mm (5.40 mm), 1.00 mm (1.04 mm), and 0.96 mm (0.93 mm) in theX,YandZdirections, respectively, using the system response matrix with (without) DOI modeling. Indicated by the Derenzo phantom imaging, the spatial resolution was ∼3.0 mm, <1.2 mm, and <1.2 mm in theX,YandZdirections. The system sensitivity was 6.87%, 4.89% and 3.37% with an energy window of 100-800, 250-750 and 350-650 keV, respectively. The scatter fraction was 26.43%, and the peak NECR was 162.6 kcps at 24.1 MBq for the modified rat-like phantom. As for the recovery coefficients, they ranged from 0.15 to 1.04 for rods between 1 and 5 mm obtained with a NEMA image quality phantom. The spill-over ratio for the air-filled and water-filled chamber was 0.05 and 0.11, respectively. DH-Mammo PET can provide more image details in clinical experiments and fulfil a fast scan with 60-120 s acquisition time.Significance. Good spatial resolution and high sensitivity of DH-Mammo PET would enable fast and accurate PET imaging of the breast. Besides, combining the DH-Mammo PET with the diffuse optical tomography would make full use of tumor metabolic imaging and tissue endogenous optical imaging, which would improve the accuracy of early clinical diagnosis of small lesions of breast cancers.

Hybrid model of photon propagation based on the analytical and Monte Carlo methods for a dual-head PET system.

The construction of photon propagation has a close relationship with the quality of reconstructed images. The classical Monte Carlo (MC) based method can model the photon propagation precisely, but it is time-consuming. The analytical method can often quickly construct a model, but its precision is a problem. How to fully exploit the advantages of the MC simulation and analytical model is an open problem. Inspired by the characteristics of the depth of interaction (DOI) detectors, which can help confirm the deposited position of a photon with DOI-encoding technology, we virtually discretize each crystal into several subcrystals to obtain the statistical distribution by MC-based simulation. Then, the statistical distribution is combined with a spatially variant solid-angle model. This combination strategy provides a hybrid model to describe photon propagation with relatively high accuracy and low computational cost. Three discretization schemes are compared to optimize the constructed photon propagation model. Several experiments are carried out to evaluate the performance of the proposed hybrid method. The metrics of full width at half maximum (FWHM), contrast recovery (CR), and coefficient of variation (COV) are adopted to quantitate the imaging results. The classical MC-based method is compared as a gold-standard reference. When a crystal is divided into two discretized positions, the convergent tendencies of CRs and COVs are consistent with that based on MC simulation method, respectively. In terms of FWHMs, the resolutions of using the MC-based model and the proposed hybrid model are 0.71 mm and 0.68 mm in the direction parallel to the detector head, respectively. This indicates the potential of the proposed method in positron emission tomography imaging.

Design, Synthesis and Biological Evaluation of Anti-tuberculosis Agents based on Bedaquiline Structure.

BACKGROUND: Bedaquiline is a novel anti-tuberculosis drug that inhibits Mycobacterial ATP synthase. However, studies have found that bedaquiline has serious side effects due to high lipophilicity. Recently, the complete structure of ATP synthase was first reported in the Journal of Science. OBJECTIVE: The study aimed to design, synthesise and carry out biological evaluation of antituberculosis agents based on the structure of bedaquiline. METHODS: The mode of action of bedaquiline and ATP synthase was determined by molecular docking, and a series of low lipophilic bedaquiline derivatives were synthesized. The inhibitory activities of bedaquiline derivatives towards Mycobacterium phlei 1180 and Mycobacterium tuberculosis H37Rv were evaluated in vitro. A docking study was carried out to elucidate the structureactivity relationship of the obtained compounds. The predicted ADMET properties of the synthesized compounds were also analyzed. RESULTS: The compounds 5c3, 6a1, and 6d3 showed good inhibitory activities (MIC=15.62 ug.mL-1). At the same time, the compounds 5c3, 6a1, and 6d3 also showed good drug-like properties through molecular docking and ADMET properties prediction. CONCLUSION: The results of in vitro anti-tuberculosis activity assays, docking studies and ADMET predictions indicate that the synthesized compounds have potential antifungal activity, with compounds 6a1 being further optimized and developed as lead compounds.

Power law relations in earthquakes from microscopic to macroscopic scales.

Understanding the physics of earthquakes is a crucial step towards improving the prediction accuracy of earthquakes. Scale invariance or fractal features are often reported in earthquakes, such as the size distribution of earthquakes, the spatial distribution of hypocenters, and the frequency of aftershocks. Here we assess whether other key parameters and quantities involved in earthquakes also conform to the power law. By analyzing a large amount of data collected from the laboratory experiments and field monitoring of earthquakes, we find that the crack density on the two sides of small scale fracture or large scale fault decreases with increasing distance following the power law, and the crack number-crack length distribution is also scale invariant like natural faults. Besides, the earthquake b-value is found to decrease with increasing stress in a power law in the brittle regime of the Earth's crust. The friction coefficient for dry fault and gouges or for partially saturated gouges decreases with the increasing effective normal stress in a power law. The stress dependency of b-value and friction coefficient is dictated by different mechanisms. Our findings will advance the understanding of earthquake physics, and will enable us to better model, predict and conduct hazard assessment of earthquakes.

Comparison of GPU reconstruction based on different symmetries for dual-head PET.

PURPOSE: Dual-head positron emission tomography (PET) scanners have increasingly attracted the attention of many researchers. However, with the compact geometry, the depth-of-interaction blurring will reduce the image resolution considerably. Monte Carlo (MC)-based system response matrix (SRM) is able to describe the physical process of PET imaging accurately and improve reconstruction quality significantly. The MC-based SRM is large and precomputed, which leads to a longer image reconstruction time with indexing and retrieving precomputed system matrix elements. In this study, we proposed a GPU acceleration algorithm to accelerate the iterative reconstruction. METHODS: It has been demonstrated that the line-of-response (LOR)-based symmetry and the Graphics Processing Unit (GPU) technology can accelerate the reconstruction tremendously. LOR-based symmetry is suitable for the forward projection calculation, but not for the backprojection. In this study, we proposed a GPU acceleration algorithm that combined the LOR-based symmetry and voxel-based symmetry together, in which the LOR-based symmetry is responsible for the forward projection, and the voxel-based symmetry is used for the backprojection. RESULTS: Simulation and real experiments verify the efficiency of the algorithm. Compared with the CPU-based calculation, the acceleration ratios of the forward projection and the backprojection operation are 130 and 110, respectively. The total acceleration ratio is 113×. In order to compare the acceleration effect of the different symmetries, we realized the reconstruction with the voxel-based symmetry and the LOR-based symmetry strategies. Compared with the LOR-based GPU reconstruction, the acceleration ratio is 3.5×. Compared with the voxel-based GPU reconstruction, the acceleration ratio is 12×. CONCLUSION: We have proposed a new acceleration algorithm for the dual-head PET system, in which both the forward and backprojection operations are accelerated by GPU.

Influence of Rotation Increments on Imaging Performance for a Rotatory Dual-Head PET System.

For a rotatory dual-head positron emission tomography (PET) system, how to determine the rotation increments is an open problem. In this study, we simulated the characteristics of a rotatory dual-head PET system. The influences of different rotation increments were compared and analyzed. Based on this simulation, the imaging performance of a prototype system was verified. A reconstruction flowchart was proposed based on a precalculated system response matrix (SRM). The SRM made the relationships between the voxels and lines of response (LORs) fixed; therefore, we added the interpolation method into the flowchart. Five metrics, including spatial resolution, normalized mean squared error (NMSE), peak signal-to-noise ratio (PSNR), contrast-to-noise (CNR), and structure similarity (SSIM), were applied to assess the reconstructed image quality. The results indicated that the 60° rotation increments with the bilinear interpolation had advantages in resolution, PSNR, NMSE, and SSIM. In terms of CNR, the 90° rotation increments were better than other increments. In addition, the reconstructed images of 90° rotation increments were also flatter than that of 60° increments. Therefore, both the 60° and 90° rotation increments could be used in the real experiments, and which one to choose may depend on the application requirement.

Cone Beam X-Ray Luminescence Tomography Imaging Based on KA-FEM Method for Small Animals.

Cone beam X-ray luminescence tomography can realize fast X-ray luminescence tomography imaging with relatively low scanning time compared with narrow beam X-ray luminescence tomography. However, cone beam X-ray luminescence tomography suffers from an ill-posed reconstruction problem. First, the feasibility of experiments with different penetration and multispectra in small animal has been tested using nanophosphor material. Then, the hybrid reconstruction algorithm with KA-FEM method has been applied in cone beam X-ray luminescence tomography for small animals to overcome the ill-posed reconstruction problem, whose advantage and property have been demonstrated in fluorescence tomography imaging. The in vivo mouse experiment proved the feasibility of the proposed method.

Meta-analysis of the associations between TNF-α or IL-6 gene polymorphisms and susceptibility to lung cancer.

BACKGROUND: Several studies have indicated an association between tumor necrosis factor-alpha (TNF-α) or interleukin (IL)-6 gene polymorphisms and lung cancer risk. However, the conclusions remain controversial. METHODS: An English literature screening about case-control trials with regard to TNF-α (-308G/A) or IL-6 (174G/C) polymorphisms and lung cancer susceptibility was performed on PubMed, EMBASE, and EBSCO until November 2012. The pooled odds ratio (OR) and 95% confidence intervals (CI) were calculated using STATA 11.0. Sensitivity analysis was performed by sequential omission of individual studies. Publication bias was evaluated by Egger's linear regression test and funnel plots. RESULTS: Eight eligible studies, including 1,690 patients and 1,974 controls, were identified in this meta-analysis. Compared with the control, no significant association was revealed between TNF-α-308G/A (GG + GC vs. CC: OR = 1.10, 95% CI: 0.73 to 1.64; GG vs. GC + CC: OR = 1.02, 95% CI: 0.81 to 1.27; GC vs. CC: OR = 1.13, 95% CI: 0.73 to 1.77; GG vs. CC: OR = 1.04, 95% CI: 0.80 to 1.36; G vs. C: OR = 1.03, 95% CI: 0.90 to 1.18) or IL-6 174G/C (GG + GC vs. CC: OR = 1.10, 95% CI: 0.73 to 1.64; GG vs. GC + CC: OR = 1.02, 95% CI: 0.81 to 1.27; GC vs. CC: OR = 1.13, 95% CI: 0.73 to 1.77; GG vs. CC: OR = 1.04, 95% CI: 0.80 to 1.36; G vs. C: OR = 1.03, 95% CI: 0.90 to 1.18) and lung cancer risk. The pooled OR remained unchanged after removing the maximum-weight study and no publication bias was observed. CONCLUSIONS: The study raises the possibility of no correlation between the polymorphisms of the two genes and lung cancer susceptibility. However, further researches with large-sample or subgroup analyses are necessary to validate the conclusions.

Molecular cloning, characteristics and low temperature response of raffinose synthase gene in Cucumis sativus L.

Raffinose synthase (RS, EC2.4.1.82) is one of the key enzymes that channels sucrose into the raffinose family oligosaccharides (RFOs) biosynthetic pathway. However, the gene encoding RS is poorly characterized in cucumber (Cucumis sativus L.), which is a typical RFOs-translocating plant species. Here we isolated the gene encoding RS (CsRS) from the leaves of cucumber plants. The complete cDNA of CsRS consisted of 2552 nucleotides with an open reading frame encoding a polypeptide of 784 amino acid residues. Reverse transcription-polymerase chain reaction and RNA hybridization analysis revealed that expression of CsRS was the highest in leaves followed by roots, fruits, and stems. The RS activity was up-regulated and the raffinose content was high in the leaves of transgenic tobacco with over-expression of CsRS, while both the RS activity and the raffinose content decreased in the transgenic cucumber plants with anti-sense expression of CsRS. The expression of CsRS could be induced by low temperature and exogenous phytohormone abscisic acid (ABA). In cucumber growing under low temperature stress, CsRS expression, RS activity and raffinose content increased gradually in the leaves, the fruits, the stems and the roots. The most notable increase was observed in the leaves. Similarly, the expression of CsRS was induced in cucumber leaves and fruits with 200 µM and 150 µM ABA treatments, respectively.

Cognitive decline following major surgery is associated with gliosis, ß-amyloid accumulation, and τ phosphorylation in old mice.

OBJECTIVE: Elderly patients undergoing major surgery often develop cognitive dysfunction and the mechanism of this postoperative complication remains elusive. We sought to determine whether postoperative cognitive dysfunction in old mice is associated with the pathogenesis of Alzheimer's disease. DESIGN: Prospective, randomized study. SETTING: University teaching hospital-based research laboratory. SUBJECTS: One-hundred and twenty C57BL/6 14-mo-old male mice (weighing 30-40 g). INTERVENTIONS: Mice received intraperitoneal injections of either vehicle or Celastrol (a potent anti-inflammatory compound) for 3 days before undergoing sham surgery or partial hepatectomy, on the surgery day, and for a further 4 days after surgery. Cognitive function, hippocampal neuroinflammation, and pathologic markers of Alzheimer's disease were assessed 1 day after surgery day 1, 3, or 7. MEASUREMENTS AND MAIN RESULTS: Cognitive impairment following surgery was associated with the appearance of certain pathologic hallmarks of Alzheimer's disease: microgliosis, astrogliosis, enhanced transcriptional and translational activity of ß-amyloid precursor protein, ß-amyloid production, and τ protein hyperphosphorylation in the hippocampus. Surgery-induced changes in cognitive dysfunction were prevented by the administration of Celastrol as were changes in ß-amyloid and τ processing. CONCLUSIONS: These data suggest that surgery can provoke astrogliosis, ß-amyloid accumulation, and τ phosphorylation in old subjects, which is likely to be associated with the cognitive decline seen in postoperative cognitive dysfunction.

Characterizing large-area electro-optic crystals toward two-dimensional real-time terahertz imaging.

We have characterized the homogeneity of large-area (>10 mm x 10 mm) CdTe(110) and ZnTe(110) crystals using a raster electro-optic scanning method to assess their usability in two-dimensional electro-optic terahertz (THz) imaging with parallel read out. The spatial variation in the detected THz signal (at 0.2 and 0.645 THz, respectively) is due to nonuniform residual birefringence and scattering. For CdTe, this depends critically on the growth method, and has an important contribution from slip planes in the crystals, as is evident in the scanned images. For the highest-quality CdTe(110) crystals investigated, the rms signal variations are less than 15%, comparable to those for ZnTe(110). For electro-optic scanning, we introduce a hybrid measurement system based on a fs Nd:glass laser and a continuous-wave electronic THz source.