Attenuation Distribution Research Articles

Estimating Annual Temperate Rain Attenuation Distributions at 20/40 GHz With a High-Resolution Numerical Weather Prediction Model

Earth-space communications are to make use of higher frequencies, at and above 20 GHz, to offer new services and increased data rates. A consequence is a strong attenuation of the carrier waves by the troposphere, particularly during rain events. The statistical characterization of the rain attenuation on high-frequency channels is thus paramount to their link budget. Traditionally this knowledge is obtained via long-term ground measurements of spaceborne beacon signals. Here, simulated results based on numerical weather prediction models are considered as an alternative. A comparison is given based on two years of beacon data at 20 and 40 GHz in Toulouse (France). Four parametrizations of the weather research forecasting model's microphysics are tested: the best performances are achieved with the NSSL-2 moment scheme.

Bioaccumulation, internal distribution and toxicity of bisphenol S in the earthworm Eisenia fetida

Due to the strict rules and restrictions on the utilization of bisphenol A (BPA) around the world, an emerging endocrine disrupting chemical, bisphenol S (BPS) has been widely utilized as a substitute and frequently detected in the environment, even in the human body. Although it has been widely studied in the aquatic systems, the fate and toxicological effect of BPS in soil invertebrates are poorly known. This study presented a comprehensive exploration into the attenuation, bioaccumulation, and physiological distribution of BPS in an ecologically significant soil invertebrate, as well as its subsequent ecotoxicological effect to earthworm for the first time. The E. fetida could promote the BPS attenuation in soil, with degradation rates of 92.8 ± 1.6 % and 98.6 ± 1.1 % at dosage of 1.0 mg/kg dry weight soil (DWS) and 0.1 mg/kg DWS, respectively. The bioaccumulation of BPS in the earthworm was up to 111.6 ± 6.0 mg/kg lipid and 12.9 ± 2.9 mg/kg lipid with the initial dosage of 1.0 mg/kg DWS and 0.1 mg/kg DWS, respectively. Furthermore, BPS could induce oxidative stress and the process of antioxidant defense in earthworm cells at relatively high dose (1.0 mg/kg DWS and 10.0 mg/kg DWS), suggesting potential risks of BPS to the soil environment. This study could contribute to a more in-depth understanding of the fate of BPS in soil-earthworm system, and indicate a necessity for better understanding the environmental fate and ecological risks of BPA substitutes in the future.

Abstract 319: Computational Analysis Of Brain Imaging To Predict Post-arrest Brain Death

Background: Grey-white matter ratio ( GWR) can estimate severity of cerebral edema after cardiac arrest and predict progression to brain death. Current approaches to calculating GWR have variable interrater reliability. We tested if a computational technique to quantify the distribution of whole-brain x-ray attenuation at hospital admission could predict ultimate progression to brain death. Methods: We identified in- and out-of-hospital post-arrest patients at our single center treated between 2018-2019. We extracted demographic data from our registry and Digital Imaging and Communication in Medicine (DICOM) files for the first post-arrest CT. We analyzed the 17th slice of each DICOM, corresponding to the level of the basal ganglia. We extracted the 512x512 array of Hounsfield units (HU). We excluded HU >40 or <10 to focus on brain tissue densities. We summarized each patient’s distribution of HU and calculated the variance as a proxy for GWR. We randomly divided our data into 75% training set and 25% test set, used univariate logistic regression to predict brain death, identified a highly specific cutoff to rule out progression to brain death, and calculated test set sensitivity and specificity at this cutoff. We performed all analyses using Python. Results: Of 413 included patients, 163 (39%) were female, median [IQR] age was 63 [52 - 73] years, and 39 (9%) progressed to brain death. CTs were obtained a median [IQR] of 4.47 [3.03 to 6.35] hours post-arrest. HU variation predicted brain death with an area under the receiver operating characteristic curve (AUROC) of 0.81 in the training set and 0.88 in the test set. The odds ratio (OR) of progression to brain death with decreasing HU variation was 0.85 (95% confidence interval [CI], 0.80 - 0.91; P < 0.001). A cutoff of 53.9 had a sensitivity of 36% (95% CI, 30.10% to 41.33%) at 97% specificity (95% CI, 89.91% to 100%) in the training set and a sensitivity of 45% (95% CI, 34.63% to 54.73%) at 100% specificity in the test set. Conclusion: Preserved HU variation excludes progression to brain death in comatose post-arrest patients with high specificity.

CT imaging findings in lung transplant recipients with COVID-19.

ObjectivesOur goal was to compare the chest computed tomography (CT) imaging findings of COVID-19 in lung transplant recipients (LTR) and a group of non-transplanted controls (NTC).MethodsThis retrospective study included 51 consecutive LTR hospitalized with COVID-19 from two centers. A total of 75 NTC were included for comparison. Images were classified regarding the standardized RSNA category, main pattern of lung attenuation, and longitudinal and axial distribution. Quantitative CT (QCT) analysis was performed to evaluate percentage of high attenuation areas (%HAA, threshold −250 to −700 HU). CT scoring was used to measure severity of parenchymal abnormalities.ResultsThe imaging findings of COVID-19 in LTR were significantly different from controls regarding the RSNA classification and pattern of lung attenuation. LTR had a significantly higher proportion of patients with an indeterminate pattern on CT (0.31 vs. 0.11, p = 0.014). The most frequent pattern of attenuation in LTR was predominantly consolidation (0.39 vs. 0.22, p = 0.144) followed by a mixed pattern of ground-glass opacities (GGO) and consolidation (0.37 vs. 0.20, adjusted p = 0.102). On the other hand, the most common pattern in NTC was GGO predominant (0.58 vs. 0.24 of LTR, p = 0.001). LTR had significantly more severe parenchymal disease measured by CT score and %HAA by QCT (0.372 ± 0.08 vs. 0.148 ± 0.06, p < 0.001).ConclusionThe most frequent finding of COVID-19 in LTR is a predominant pattern of consolidation. Compared to NTC, LTR more frequently demonstrated an indeterminate pattern according to the RSNA classification and more extensive lung abnormalities on QCT and semi-quantitative scoring.Key Points• The most common CT finding of COVID-19 in LTR is a predominant pattern of consolidation followed by a mixed pattern of GGO and consolidation, while controls more often have a predominant pattern of GGO.• LTR more often presents with an indeterminate pattern of COVID-19 by RSNA classification than controls; therefore, molecular testing for COVID-19 is essential for LTR presenting with lower airway infection independently of imaging findings.• LTR had more extensive disease by semi-quantitative CT score and increased percentage areas of high attenuation on QCT.

Predicting infrasound transmission loss using deep learning

SUMMARY Modelling the spatial distribution of infrasound attenuation (or transmission loss, TL) is key to understanding and interpreting microbarometer data and observations. Such predictions enable the reliable assessment of infrasound source characteristics such as ground pressure levels associated with earthquakes, man-made or volcanic explosion properties, and ocean-generated microbarom wavefields. However, the computational cost inherent in full-waveform modelling tools, such as parabolic equation (PE) codes, often prevents the exploration of a large parameter space, that is variations in wind models, source frequency and source location, when deriving reliable estimates of source or atmospheric properties—in particular for real-time and near-real-time applications. Therefore, many studies rely on analytical regression-based heuristic TL equations that neglect complex vertical wind variations and the range-dependent variation in the atmospheric properties. This introduces significant uncertainties in the predicted TL. In the current contribution, we propose a deep learning approach trained on a large set of simulated wavefields generated using PE simulations and realistic atmospheric winds to predict infrasound ground-level amplitudes up to 1000 km from a ground-based source. Realistic range dependent atmospheric winds are constructed by combining ERA5, NRLMSISE-00 and HWM-14 atmospheric models, and small-scale gravity-wave perturbations computed using the Gardner model. Given a set of wind profiles as input, our new modelling framework provides a fast (0.05 s runtime) and reliable (∼5 dB error on average, compared to PE simulations) estimate of the infrasound TL.

Quantitative Evaluation of Chronic Obstructive Pulmonary Disease and Risk Prediction of Acute Exacerbation by High-Resolution Computed Tomography.

Objective It is imperative to popularize the tertiary prevention of chronic obstructive pulmonary disease (COPD) and to improve the diagnosis and treatment. Methods COPD patients were divided into mild (n = 18), moderate (n = 20), severe (n = 24), and extremely severe (n = 22) groups for performing high-resolution computed tomography (HRCT) and pulmonary function test. Serum procalcitonin (PCT) and high-sensitivity C-reactive protein (hs-CRP) were detected, and the occurrence rate of acute exacerbation COPD (AECOPD) was recorded during a 12-months follow-up period. Results With an increase in the severity grade, the HRCT indexes, including emphysema index (EI), 1st and 15th percentile of inspiratory attenuation distribution (Perc1 and Perc15), ratio of expiratory/inspiratory mean lung density (MLDex/in) and lung volume (LVex/in), and ratio of the wall thickness to the outer diameter of the lumen (TDR), as well as percentage of the wall area to the total cross-sectional area (WA%) were increased with a decreased change in relative lung volume with attenuation values between −860 and −950 HU (RVC−860to −950) and lumen area (Ai). These were correlated with the ratio of forced expiratory volume in 1 sec (FEV1) over forced vital capacity (FVC) (FEV1/FVC), the percentage of FEV1 the predicted value (FEV1%), and ratio of residual volume to total lung volume (RV/TLC). Body mass index, MLDex/in, FEV1%, FEV1/FVC, and PCT had a predictive value to AECOPD, with the combined AUC of 0.812. Conclusions HRCT imaging effectively classifies the severity of COPD, which combined with BMI, PFT, and serum PCT can predict the risk of AECOPD.

Алгоритм синтеза пленочного аттенюатора с равномерным рассеянием мощности по его длине

The problem of synthesizing a film attenuator made by applying an absorbing material to a conductor is considered. Since the absorbing material has a parameter of maximum dissipated power per unit area, then when synthesizing an attenuator to attenuate high powers, the problem of exceeding the maximum dissipated power per unit area may arise. A sectional attenuator structure has been proposed, which is a set of sections having different attenuation to reduce the power dissipated per unit area. An algorithm for the synthesis of a sectional attenuator is proposed. The attenuator sections are rectangles of various widths. The attenuation distribution is performed using the Taylor series expansion of mathematical functions. The properties of the functions used to distribute the attenuation related to the problem under consideration were considered. The graphs of the dependence of power on the attenuator section are presented. Power distribution has been confirmed by simulation results. Theoretical calculations were confirmed by simulation results in the CST Microwave Studio software.

Global Formulation of the Synthetic Storm Technique Oriented to Satellite Link–Budget Design

We have updated the global Synthetic Storm Technique (referred to as the global SST) by reformulating it according to a larger database of rain rate time series collected in several sites in different climatic regions. For each site, the average annual probability distribution of rain attenuation obtained with the global SST, PSST,gloA, in a slant path, was compared with that given by the full SST, PSSTA, which we have considered as experimental data. The test was performed for frequency ranging from 10 to 100 GHz, for elevation angle θ ranging from 20° to 60° and for annual probabilities 10% to 0.01%. The global SST tends to underestimate the attenuation by approximately 10% for elevation angle θ≤30° and about 20% for 30°&lt;θ&lt;60° in the probability range 10% to 0.1%, and approximately 15% in the probability range 0.1% to 0.01%. For any probability, the error is zero for θ=90° because at the zenith, the global SST coincides with the full SST.

Electromagnetic attenuation distribution in a three-dimensional amorphous carbon matrix with highly dispersed Fe/Fe3C@graphite-C nanoparticles

The dielectric-magnetic synergistic effect can be achieved by dielectric relaxation and magnetic resonances in composites of carbon materials and magnetic particles. However, there is no direct evidence demonstrating the distribution of electromagnetic energy attenuation in the microstructure of composites. Herein, an amorphous carbon matrix with dispersed Fe/Fe3C@graphite-C was fabricated via a facile route. The distribution of the magnetic vector loss and electric vector loss in the hierarchical structures was revealed by numerical simulation. The content and dispersion of magnetic particles as well as the morphology of the amorphous carbon can be tuned. The 3D amorphous carbon matrix with highly dispersed Fe/Fe3C@graphite-C nanoparticles provided the strongest absorption of −69.0 dB and an effective response bandwidth (RL ≤ −10 dB) of 7.06 GHz. The numerical simulation revealed that the magnetic vector loss originated only from the core of Fe/Fe3C, and the electric vector loss was distributed throughout the structure, especially in the graphite-C shell, the interface between graphite-C and carbon nanoflakes, and the junction of different carbon nanoflakes. This work not only reveals the distribution of electromagnetic loss but also supports the theoretical analysis of the electromagnetic wave attenuation mechanism in composites, which provides direction for the future design of composites.

Statistical distribution of wave heights attenuation by entrained air bubbles in the surf zone

The paper focuses on the wave height distribution functions for long-term behavior of significant wave height, probability density function, Rayleigh distribution, depth-limited wave height distributions, etc. We have introduced the air bubble effects in the surf zone wave parameters, and the wave height distribution has been derived from the Rayleigh distribution. The calculated statistical wave height distributions by the present model indicate a good agreement with the field data than the Rayleigh distribution. Furthermore, the computed probability densities of the wave heights have been reduced considerably by the air bubble effects, making the wave heights lower than those determined by the Rayleigh distribution. It is also observed that the Rayleigh distribution overestimates large pressure amplitudes, but the present model and the Weibull distribution agree well with the collected field data. Finally, the proposed model performs less normalized root-mean-square error in predicting wave height statistics.

Comparison of semi-airborne transient electromagnetic data from double-line and single-line grounded-wire sources

The semi-airborne transient electromagnetic method (TEM) involves a ground-based electrical source and an airborne magnetic field component receiver and is an effective method for exploration in complex terrains. However, the ground transmitter selection for these methods is typically challenging. In the present study, we examine the magnetic field responses of double-line and single-line source devices. Response attenuation and plane distribution are utilized to analyze and compare the characteristics of the two sources. In the double-line source, the inline and cross-line components of magnetic field are axisymmetric, with distribution characteristics of six-petaled flowers. The vertical component exhibits a four-quadrant distribution comparable to that of the x component in the single-line source; the components are generated separately or jointly by current-carrying wires and grounding ends. Although the double-line source is generally characterized by weaker response intensities than the single-line source, its components (especially the cross-line and vertical components) exhibit higher resolutions for low- and high-resistivity targets. Thus, with adequate measured signal strength, the double-line source is preferable for semi-airborne TEM involving an electrical source.

Millimetre-Wave Propagation Channel Based on NYUSIM Channel Model With Consideration of Rain Fade in Tropical Climates

The impact of atmospheric attenuation on wireless communication links is much more severe and complicated in tropical regions. That is due to the extreme temperatures, intense humidity, foliage and higher precipitation rain rates with large raindrop sizes. This paper investigates the propagation of the mm-waves at the 38 GHz link based on real measurement data collected from outdoor microcellular systems in Malaysia. The rainfall rate and received signal level have been measured simultaneously in 1-minute time intervals for one year over a 300 m path length. The rain attenuation distributions at different percentages of exceedance time have been compared with the modified distance factor of the ITU-R P.530-17 model. The average link availability calculated with the measured rain rates has been analysed. Additionally, the key propagation channel parameters such as the path loss, path loss exponent, Rician K-factor, root mean square, delay spread and received power have been investigated considering the rain attenuation. These propagation channel parameters have been analysed using MATLAB software and explained with the help of the latest NYUSIM channel model software package (Version 2.0). The analysis results have been classified considering rain attenuation, antenna setup, link distances, antenna height and antenna gain. The outcomes revealed that the rain fade predicted by applying the modified distance factor provides high consistency with the measured fade in Malaysia and several available measurements from different locations. The large-scale path loss model in the NYUSIM simulation result was around 126.23 dB by considering the rain attenuation effects on the 300m path length. This work shows that the NYUSIM channel model offers more accurate rendering results of path loss for omnidirectional and directional antenna transmissions without rain fade. This study proves that the ability to provide good coverage and ultra-reliable communication for outdoor and outdoor-to-indoor applications during rain in tropical regions must be sufficiently addressed.

Optical attenuation characteristics of Lake Daye, Hubei Province based on remote sensing inversion of Landsat 8 OLI

水体光学衰减特性直接影响湖泊的清澈程度和沉水植被的生存，利用遥感技术获取湖泊光学衰减分布特性能极大提高效率.基于2017—2019年的原位调查数据，利用Landsat 8 OLI影像开发了大冶湖水体光学衰减系数（K_d）的遥感反演模型，并分析大冶湖水体K_d的多年时空分布特性与驱动机制，以期为大冶湖流域的修复与管理提供参考.结果表明：波段比二次模型K_d=9.61（B1/B4）²-2.41（B1/B4）-6.40效果最好，精度达到R²=0.79，MAPE=23.9%，RMSE=0.89 m^-1.大冶湖水体K_d值的主要影响因素为悬浮物和浊度等，其次为有色溶解性有机物和叶绿素a.大冶湖K_d值分布在空间上由西向东逐渐递减，但局部也受到风速、陆源输入、人为活动和微生物活动等的影响，季节上平均以夏季最高、冬季最低.2013年以来大冶湖水体K_d值整体呈现下降趋势.;The optical attenuation characteristics of water directly affect the clarity of lake and the survival of submerged macrophytes. Using the way of remote sensing to obtain the optical attenuation distribution characteristics of lakes can greatly improve the efficiency. Lake Daye, located in Huangshi City, Hubei Province, is a typical shallow lake in the middle reaches of the Changjiang (Yangtze) River. Based on the in-situ survey data from 2017 to 2019, the remote sensing inversion model of Lake Daye water optical attenuation coefficient (K_d) is developed by using Landsat 8 OLI images, and the multi-year temporal and spatial distribution characteristics and driving mechanism of K_d in Lake Daye are analyzed, so as to provide reference for the restoration and management of Lake Daye basin. The results show that:the band ratio quadratic model was the best model (K_d=9.61 (B1/B4) ²-2.41 (B1/B4) -6.40), and its accuracy was R²=0.79, MAPE=23.9%, RMSE=0.89 m^-1. The main influencing factors of K_d of Lake Daye were suspended solids and turbidity, followed by chromophoric dissolved organic matter and chlorophyll-a. Moreover, the K_d value of Lake Daye decreased gradually from west to east in space, but it was also affected by wind speed, land-based input, human activities and microbial activities in some parts. The average of K_d is highest in summer and lowest in winter. Since 2013, the K_d value of Lake Daye has shown an overall downward trend.

Adjoint envelope tomography for scattering and absorption using radiative transfer theory

SUMMARY To investigate the small-scale elastic structure of the subsurface at length scales below the resolution limits of waveform tomography, envelopes of high-frequency scattered seismic waveforms have been used with a variety of approaches. However, a rigorous framework for the iterative inversion of seismogram envelopes to image heterogeneity and high-frequency attenuation comparable to full waveform inversion (FWI) is missing. We present the mathematical framework for an iterative full envelope inversion using forward and adjoint simulations of the radiative transfer equations, in full analogy to FWI that is based on the wave equation. The forward and adjoint problems are solved by modelling 2-D multiple non-isotropic scattering in a random elastic medium with spatially variable heterogeneity and attenuation using the Monte Carlo method. Sensitivity kernels are derived for the squared difference between the full observed and modelled envelopes which is iteratively minimized with the L-BFGS method. We apply this algorithm in numerical tests in the acoustic approximation and show that it is possible to image the spatial distribution of small-scale heterogeneity and attenuation in iterative inversions. Our analysis shows that the relative importance of scattering and attenuation anomalies needs to be considered when the model resolution is assessed. The inversions confirm that the early coda is important for imaging the distribution of heterogeneity while later coda waves are more sensitive to intrinsic attenuation and we show that this dependency can be used to cope with the trade-off that exists between both material properties.

Calculation and analysis of cloud attenuation and other cloud parameters in India for earth-space links

• The cloud attenuation is higher during the SW monsoon season followed by NE monsoon, pre-monsoon and winter seasons at the places considered. • The maximum cloud attenuation of 1.67 dB/km is measured in Hyderabad by WVP-NTU cloud detection model at 24 GHz. • The WVP-NTU cloud detection model is more suitable for the five places considered as compared to the SU model. An effort is made to examine the cloud parameters over few stations in India for one year from October 2016 to September 2017. This study includes the investigation of cloud base height, cloud top height, zero degree isotherm height, number of cloud layers, cloud thickness, number of days cloud detected, cloud liquid water content and cloud attenuation at 6 GHz, 12.5 GHz and 24 GHz. Salonen Uppala (SU) model and Water Vapor Pressure-Nanyang Technological University (WVP-NTU) model are used for cloud detection using the radiosonde data at Bangalore, Hyderabad, Mumbai, Thiruvananthapuram and Chennai. The cloud parameters found using both the models are compared. WVP-NTU model shows enhanced values for most of the cloud parameters over SU model. Cloud base height calculated using these models are compared with METAR data and found that Cloud base height from WVP-NTU model matches well with METAR data. Cloud liquid water content and cloud attenuation values are calculated using the ITU-R model. The cumulative distributions (CDF) of cloud attenuation for one year are compared for the places considered. The seasonal CDFs of cloud attenuation using the WVP model are compared with the rain statistics. In this study, the maximum cloud attenuation of 1.67 dB/km is measured in Hyderabad by WVP-NTU combined ITU-R model at 24 GHz.

Interobserver agreement of interstitial lung fibrosis Reporting and Data System (ILF-RADS) at high-resolution CT.

To assess the interobserver agreement of interstitial lung fibrosis Reporting and Data System (ILF-RADS) in interpretation and categorization of interstitial lung disease (ILD) at high-resolution CT (HRCT). Retrospective analysis was performed on 65 consecutive patients (36 male and 29 female), median age 53years, who were referred to the Radiology Department, Mansoura University, in the period from July 2016 to February 2020. They were expected clinically to have diffuse lung disease and underwent HRCT of the chest. Patients had some investigations like serology, and when required surgical lung biopsy. Image analysis was done by two independent and blinded readers for the pulmonary and extra-pulmonary finding of ILF-RADS. The pulmonary findings were 13 items and extrapulmonary findings were 5 items. The score was 5 types according to ILF-RADS: ILF-RADS 0 (incomplete assessment), ILF-RADS 1 (typical UIP), ILF-RADS 2 (probable UIP), ILF-RADS 3 (indeterminate UIP), ILF-RADS 4 (CT features most consistent with non-UIP diagnosis). There was an excellent interobserver agreement of both reviewers for overall ILF-RADS (K = 0.88, P = 0.001) with 95.4% agreement. There was an excellent interobserver agreement for overall pulmonary findings (K = 0.901, 95% CI = 0.877-0.926, P = 0.001), excellent interobserver agreement for seven items including lung volume, traction bronchiectasis, nodules, cysts, consolidation, emphysema, and complications and moderate interobserver agreement for six items including reticulations, honeycomb, ground glass, mosaic attenuation, and axial and zonal distribution. There was excellent interobserver agreement for overall extra-pulmonary findings (K = 0.902, 95% CI = 0.852-0.952, P = 0.001), excellent interobserver agreement for four items including mediastinum, pleura, visible abdomen, and soft tissue and bone and moderate interobserver agreement for trachea and main bronchi. There was excellent interobserver agreement for ILF-RADS score: ILF-RADS 1 (K = 0.84, P = 0.001), ILF-RADS 3 (K = 0.881, P = 0.001), and ILF-RADS 4 (K = 0.878, 95% CI = 0.743-1.0, P = 0.001) and moderate interobserver agreement for ILF-RADS 2 (K = 0.784, P = 0.001). ILF-RADS is a reliable reporting system which can be routinely performed for standard interpretation of ILD.

Determining age and sex-specific distribution of pancreatic whole-gland CT attenuation using artificial intelligence aided image segmentation: Associations with body composition and pancreatic cancer risk

Background & aimsIncreased intrapancreatic fat is associated with pancreatic diseases; however, there are no established objective diagnostic criteria for fatty pancreas. On non-contrast computed tomography (CT), adipose tissue shows negative Hounsfield Unit (HU) attenuations (−150 to −30 HU). Using whole organ segmentation on non-contrast CT, we aimed to describe whole gland pancreatic attenuation and establish 5th and 10th percentile thresholds across a spectrum of age and sex. Subsequently, we aimed to evaluate the association between low pancreatic HU and risk of pancreatic ductal adenocarcinoma (PDAC). MethodsThe whole pancreas was segmented in 19,456 images from 469 non-contrast CT scans. A convolutional neural network was trained to assist pancreas segmentation. Mean pancreatic HU, volume, and body composition metrics were calculated. The lower 5th and 10th percentile for mean pancreatic HU were identified, examining the association with age and sex. Pre-diagnostic CT scans from patients who later developed PDAC were compared to cancer-free controls. ResultsLess than 5th percentile mean pancreatic HU was significantly associated with increase in BMI (OR 1.07; 1.03–1.11), visceral fat (OR 1.37; 1.15–1.64), total abdominal fat (OR 1.12; 1.03–1.22), and diabetes mellitus type 1 (OR 6.76; 1.68–27.28). Compared to controls, pre-diagnostic scans in PDAC cases had lower mean whole gland pancreatic HU (−0.2 vs 7.8, p = 0.026). ConclusionIn this study, we report age and sex-specific distribution of pancreatic whole-gland CT attenuation. Compared to controls, mean whole gland pancreatic HU is significantly lower in the pre-diagnostic phase of PDAC.

Breast Acoustic Parameter Reconstruction Method Based on Capacitive Micromachined Ultrasonic Transducer Array.

Ultrasound computed tomography (USCT) systems based on capacitive micromachined ultrasonic transducer (CMUT) arrays have a wide range of application prospects. For this paper, a high-precision image reconstruction method based on the propagation path of ultrasound in breast tissue are designed for the CMUT ring array; that is, time-reversal algorithms and FBP algorithms are respectively used to reconstruct sound speed distribution and acoustic attenuation distribution. The feasibility of this reconstruction method is verified by numerical simulation and breast model experiments. According to reconstruction results, sound speed distribution reconstruction deviation can be reduced by 53.15% through a time-reversal algorithm based on wave propagation theory. The attenuation coefficient distribution reconstruction deviation can be reduced by 61.53% through FBP based on ray propagation theory. The research results in this paper will provide key technological support for a new generation of ultrasound computed tomography systems.

Development of a neonate X-ray phantom for 2D imaging applications using single-tone inkjet printing.

Inkjet printers can be used to fabricate anthropomorphic phantoms by the use of iodine-doped ink. However, challenges persist in implementing this technique. The calibration from grayscale to ink density is complex and time-consuming. The purpose of this work is to develop a printing methodology that requires a simpler calibration and is less dependent on printer characteristics to produce the desired range of x-ray attenuation values. Conventional grayscale printing was substituted by single-tone printing; that is, the superposition of pure black layers of iodinated ink. Printing was performed with a consumer-grade inkjet printer using ink made of potassium-iodide (KI) dissolved in water at 1g/ml. A calibration for the attenuation of ink was measured using a commercial x-ray system at 70kVp. A neonate radiograph obtained at 70kVp served as an anatomical model. The attenuation map of the neonate radiograph was processed into a series of single-tone images. Single-tone images were printed, stacked, and imaged at 70kVp. The phantom was evaluated by comparing attenuation values between the printed phantom and the original radiograph; attenuation maps were compared using the structural similarity index measure (SSIM), while attenuation histograms were compared using the Kullback-Leibler (KL) divergence. A region of interest (ROI)-based analysis was also performed, where the attenuation distribution within given ROIs was compared between phantom and patient. The phantom sharpness was evaluated in terms of modulation transfer function (MTF) estimates and signal spread profiles of high spatial resolution features in the image. The printed phantom required 36 pages. The printing queue was automated and it took about 2h to print the phantom. The radiograph of the printed phantom demonstrated a close resemblance to the original neonate radiograph. The SSIM of the phantom with respect to that of the patient was 0.53. Both patient and phantom attenuation histograms followed similar distributions, and the KL divergence between such histograms was 0.20. The ROI-based analysis showed that the largest deviations from patient attenuation values were observed at the higher and lower ends of the attenuation range. The limiting resolution of the proposed methodology was about 1mm. A methodology to generate a neonate phantom for 2D imaging applications, using single-tone printing, was developed. This method only requires a single-value calibration and required less than 2h to print a complete phantom.

Airborne Lidar Observations of a Spring Phytoplankton Bloom in the Western Arctic Ocean

One of the most notable effects of climate change is the decrease in sea ice in the Arctic Ocean. This is expected to affect the distribution of phytoplankton as the ice retreats earlier. We were interested in the vertical and horizontal distribution of phytoplankton in the Chukchi Sea in May. Measurements were made with an airborne profiling lidar that allowed us to cover large areas. The lidar profiles showed a uniform distribution of attenuation and scattering from the surface to the limit of lidar penetration at a depth of about 30 m. Both parameters were greater in open water than under the ice. Depolarization of the lidar decreased as attenuation and scattering increased. A cluster analysis of the 2019 data revealed four distinct clusters based on depolarization and lidar ratio. One cluster was associated with open water, one with pack ice, one with the waters along the land-fast ice, and one that appeared to be scattered throughout the region. The first three were likely the result of different assemblages of phytoplankton, while the last may have been an artifact of thin fog in the atmosphere.