Attenuation Ratio Research Articles

Localization and size quantification of surface crack of concrete based on Rayleigh wave attenuation model

Damage detection is one of the most important major branches of non-destructive evaluation. In this study, a damage detection method for localization and size quantification of surface crack of concrete based on a Rayleigh wave attenuation model is proposed. A new physical Rayleigh wave attenuation model considering both the material and geometrical attenuation coefficients is developed, in which systematic search method and numerical integration are employed to solve the implicit integration function. Based on the proposed attenuation model, the difference of wave attenuation ratio at different reflection positions (i.e., crack tip and midrange) is investigated and further validated by comprehensive numerical models. It is proven that the proposed attenuation model and criterion can be successfully employed to quantitatively recognize the signals reflected from different positions of crack. With the accurate recognition of crack tip and midrange, a modified ellipse localization algorithm is proposed to determine the linear and broken-line crack endpoints and orientation in four generalized cases. The results show that the detected location and length of crack agree well with that of originally precast crack. The proposed method for crack localization and size quantification of surface crack based on the wave attenuation model shows great potential for damage severity detection of concrete structures.

Attenuation methods for quantifying gas saturation in organic-rich shale and tight gas formations

Quantitative interpretation of waveform attenuation for determining petrophysical properties remains one of the most challenging problems associated with rock physics. In this study, two effective methods are proposed to compute gas saturation in organic-rich shale and tight gas formations from full-waveform sonic attenuations. We first extract compressional (P)- and shear (S)-wave attenuations from monopole and dipole waveforms by median frequency shift and multi-frequency inversion methods, respectively. Crossplots of the P- to S-wave attenuation ratio ([Formula: see text]) and core gas saturation show a positive linear correlation. The [Formula: see text] value and the neutron-density porosity difference exhibit an identical log trend across different formations. The coincidence of these two different hydrocarbon indicators implies that [Formula: see text] is most sensitive to pore-fluid saturation and is less affected by variations in lithology. In the first method, the core-calibrated [Formula: see text] yields an accurate estimate of gas saturation. The second method is suited for the absence of core saturation data, which use the probability distribution of [Formula: see text] for the evaluation of gas saturation. Compared to conventional resistivity methods, the proposed attenuation method, as a nonelectric approach, provides a more accurate gas saturation prediction for low-resistivity reservoir rocks. Finally, we analyze the characteristics of attenuation-saturation relations in low-porosity rocks and discover the possible attenuation mechanisms.

Seismic identification of tight-oil reservoirs by using 3D rock-physics templates

Tight-oil reservoirs are classified as unconventional hydrocarbon resources, having a complex system of pores and cracks and low porosity/permeability. A good pore-crack connectivity is required for hydrocarbon production, but clay minerals filling the pores and throats may hinder the fluid migration. Thus, the combined effects of the pore-crack network and the presence of clay are the main factors controlling the reservoir properties and its storage capacity. In this study, a suite of cores was collected from a reservoir located in the north of the Songliao Basin (China), and establish their microstructure by scanning electron microscopy. Then, ultrasonic experiments were performed under in-situ conditions to analyze the influence of clay minerals and porosity on the elastic waves. The triple-porosity, differential-effective-medium and self-consistent theories were used to calculate the stiffness moduli by considering the effects of pores, cracks and clay minerals, and to analyze the influence of these reservoir properties on the P-wave attributes. According to attenuation, acoustic impedance and phase-velocity ratio, a multi-scale 3D rock-physics template was established. By using the ultrasonic, sonic-log and seismic data, the templates were calibrated and then the reservoir characteristics were estimated. Two 2D seismic lines were considered and the corresponding predicted reservoir properties were compared to the well-log data and the actual production reports, showing that the porosity and clay content predictions are consistent with these data, and that the oil production areas are all located within the high-cracked porous zones. The 3D rock-physics templates can effectively estimate the distribution of high-quality tight-oil reservoirs.

Metabolic syndrome, fatty liver, and artificial intelligence-based epicardial adipose tissue measures predict long-term risk of cardiac events: a prospective study

BackgroundWe sought to evaluate the association of metabolic syndrome (MetS) and computed tomography (CT)-derived cardiometabolic biomarkers (non-alcoholic fatty liver disease [NAFLD] and epicardial adipose tissue [EAT] measures) with long-term risk of major adverse cardiovascular events (MACE) in asymptomatic individuals.MethodsThis was a post-hoc analysis of the prospective EISNER (Early-Identification of Subclinical Atherosclerosis by Noninvasive Imaging Research) study of participants who underwent baseline coronary artery calcium (CAC) scoring CT and 14-year follow-up for MACE (myocardial infarction, late revascularization, or cardiac death). EAT volume (cm3) and attenuation (Hounsfield units [HU]) were quantified from CT using fully automated deep learning software (< 30 s per case). NAFLD was defined as liver-to-spleen attenuation ratio < 1.0 and/or average liver attenuation < 40 HU.ResultsIn the final population of 2068 participants (59% males, 56 ± 9 years), those with MetS (n = 280;13.5%) had a greater prevalence of NAFLD (26.0% vs. 9.9%), higher EAT volume (114.1 cm3 vs. 73.7 cm3), and lower EAT attenuation (−76.9 HU vs. −73.4 HU; all p < 0.001) compared to those without MetS. At 14 ± 3 years, MACE occurred in 223 (10.8%) participants. In multivariable Cox regression, MetS was associated with increased risk of MACE (HR 1.58 [95% CI 1.10–2.27], p = 0.01) independently of CAC score; however, not after adjustment for EAT measures (p = 0.27). In a separate Cox analysis, NAFLD predicted MACE (HR 1.78 [95% CI 1.21–2.61], p = 0.003) independently of MetS, CAC score, and EAT measures. Addition of EAT volume to current risk assessment tools resulted in significant net reclassification improvement for MACE (22% over ASCVD risk score; 17% over ASCVD risk score plus CAC score).ConclusionsMetS, NAFLD, and artificial intelligence-based EAT measures predict long-term MACE risk in asymptomatic individuals. Imaging biomarkers of cardiometabolic disease have the potential for integration into routine reporting of CAC scoring CT to enhance cardiovascular risk stratification.Trial registration NCT00927693.

Adrenal metastases: early biphasic contrast-enhanced CT findings with emphasis on differentiation from lipid-poor adrenal adenomas

To evaluate the accuracy of unenhanced attenuation and early biphasic contrast-enhanced computed tomography (CT) in differentiating adrenal metastases (AMs) from lipid-poor adrenal adenomas (AAs). This retrospective study included 37 patients with 50 AMs and 86 patients with 89 lipid-poor AAs. Quantitative data including the longest diameter (LD), the shortest diameter (SD), LD/SD ratio, CT attenuation values (CTu, CTa, CTv), degree of enhancement (DEAP, DEPP, DEpeak, APW, RPW), and peak enhanced/unenhanced (PE/U) CT attenuation ratio were obtained. Qualitative data including enhancement pattern, location, shape, the presence of calcification or haemorrhage, and intra-lesion necrosis were analysed. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were also calculated. The PE/U ratio (≤1.25), CTu (≥32.2 HU), DEpeak (≤43.15 HU), DEPP (≤37.65 HU), presence of intralesional necrosis, location (bilateral adrenal glands), and irregular shape were significant variables for differentiating AMs from lipid-poor AAs (p<0.05). Among them, PE/U ratio (≤1.25) was of greater value in differentiating the two adrenal diseases, with sensitivity, specificity, area under the receiver operating curve (ROC) curve (AUC) of 92%, 84%, 0.933, respectively. When at least any three of above criteria were combined, the sensitivity, specificity, PPV, and NPV for diagnosing AMs were 88%, 93%, 88%, and 88%, respectively. These seven CT criteria are conducive to differentiate AMs from lipid-poor AAs. Early biphasic contrast-enhanced CT is a high-efficient and practical imaging tool in differentiating them.

Robust underwater image enhancement method based on natural light and reflectivity.

The poor visibility of underwater images is caused not only by scattering and absorption effects but is also related to light conditions. To improve robustness, a novel underwater image enhancement method based on natural light and reflectivity is proposed. Aiming at the scattering effects of reflectivity, a dehazing process based on the non-correlation of a foreground scene and background light is first conducted. Then, a more precise reflectivity can be estimated by substituting the captured image with the dehazed image. Moreover, classical methods often regard the dehazed image as the final result, but ignore the fact that attenuated natural light and nonuniform artificial light, which lead to insufficient brightness and halo effects, are included in the dehazed image, and are not robust to all scenes. This phenomenon enables us to remove the artificial light disturbance by introducing the dehazed image in the Lambertian model, and compensate for the loss of natural light energy by exploiting the light attenuation ratio map. Thus, the least-attenuated natural light can be further derived. Experimental results demonstrate that our method is satisfactory in producing more pleasing results under various circumstances.

Robust, magnetic cellulose/Fe3O4 film with anisotropic sensory property

Fe3O4/cellulose composite films with anisotropic structure and properties were fabricated. Blend solution of Fe3O4 nanoparticles and cellulose in benzyltrimethyl ammonium hydroxide aqueous solution was subjected to magnetic orientation, followed by regeneration and mechanical stretching, leading to alignment of Fe3O4 nanoparticles as whisker or wire like aggregates in the cellulose matrix. The composite films showed magnetic and mechanical anisotropy with higher saturated magnetization, remanence and tensile strength in the direction parallel to the orientation direction, due to the anisotropic structure. When used as magnetic sensors, the composite films demonstrated anisotropic response to external magnetic field, namely, the current attenuation ratio in the perpendicular direction was 15.8%, while in the parallel direction it was 31.1% which was almost double of that in the perpendicular direction. The composite films also possess fast responsiveness and excellent reproducibility, potential as magnetic sensors and smart devices. In addition, the composite films also displayed excellent UV shielding property. The present work not only provides a facile pathway to fabricate smart devices, but also takes advantage of the bioresource, demonstrating potential in sustainability.

Whole-Body Low-Dose CT in Multiple Myeloma: Diagnostic Value of Appendicular Medullary Patterns of Attenuation.

OBJECTIVE. The purpose of this article is to analyze whole-body low-dose CT-detected appendicular medullary patterns of attenuation in patients with newly diagnosed multiple myeloma and to determine the diagnostic performance of whole-body low-dose CT in detecting diffuse marrow infiltration. MATERIALS AND METHODS. A total of 76 patients with myeloma who underwent whole-body low-dose CT and spinal MRI at initial assessment were retrospectively analyzed. The medullary cavities of femurs and humeri were evaluated qualitatively and quantitatively on CT. Medullary attenuation and SD-to-mean attenuation ratio were recorded for each long bone. The pattern of marrow involvement on spinal MRI was used as reference. The chi-square test was used to evaluate the relationship between the CT-based appendicular medullary cavity pattern and the MRI pattern, and ROC analysis was performed to assess the diagnostic accuracy of CT attenuation measurements for the differentiation between diffuse and mixed CT-based appendicular medullary cavity patterns. RESULTS. Medullary attenuation differed significantly among mixed, nodular, and diffuse CT-based appendicular medullary cavity patterns in the femurs (mean, 34.23 HU and range, 15-61 HU; mean, 66.26 HU and range, 26-104 HU; mean, 92.80 HU and range, 53-127 HU, respectively) and humeri (mean, 22.18 HU and range, 9-41; mean, 61.18 HU and range, 23-93 HU; mean, 77.50 and range, 25-105 HU, respectively). To discriminate between diffuse and mixed CT-based appendicular medullary cavity patterns, optimal cutoff attenuation values were 63 HU (sensitivity, 97.7%; specificity, 100.0%) for the femurs, and 52 HU (sensitivity, 97.4%; specificity, 100.0%) for the humeri. A total of 24 of 30 (80.0%) patients with a diffuse MRI pattern showed a diffuse CT-based appendicular medullary cavity pattern on whole-body low-dose CT, and all patients with a diffuse CT-based appendicular medullary cavity pattern also showed a diffuse pattern on MRI. CONCLUSION. According to analysis of peripheral medullary patterns of attenuation, whole-body low-dose CT can identify patients with multiple myeloma with diffuse marrow involvement.

Prognostic value of non-alcoholic fatty liver disease for predicting cardiovascular events in patients with diabetes mellitus with suspected coronary artery disease: a prospective cohort study

BackgroundRisk stratification of cardiovascular events in patients with type 2 diabetes mellitus (T2DM) has not been established. Coronary artery calcium score (CACS) and non-alcoholic fatty liver disease (NAFLD) are independently associated with cardiovascular events in T2DM patients. This study examined the incremental prognostic value of NAFLD assessed by non-enhanced computed tomography (CT) in addition to CACS and Framingham risk score (FRS) for cardiovascular events in T2DM patients.MethodsThis prospective pilot study included 529 T2DM outpatients with no history of cardiovascular disease who underwent CACS measurement because of suspected coronary artery disease. NAFLD was defined on CT images as a liver:spleen attenuation ratio < 1.0. Cardiovascular events were defined as cardiovascular death, nonfatal myocardial infarction, late coronary revascularization, nonfatal stroke, or hospitalization for heart failure.ResultsAmong 529 patients (61% men, mean age 65 years), NAFLD was identified in 143 (27%). Forty-four cardiovascular events were documented during a median follow-up of 4.4 years. In multivariate Cox regression analysis, NAFLD, CACS, and FRS were associated with cardiovascular events (hazard ratios and 95% confidence intervals 5.43, 2.82–10.44, p < 0.001; 1.56, 1.32–1.86, p < 0.001; 1.23, 1.08–1.39, p = 0.001, respectively). The global χ2 score for predicting cardiovascular events increased significantly from 27.0 to 49.7 by adding NAFLD to CACS and FRS (p < 0.001). The addition of NAFLD to a model including CACS and FRS significantly increased the C-statistic from 0.71 to 0.80 (p = 0.005). The net reclassification achieved by adding CACS and FRS was 0.551 (p < 0.001).ConclusionsNAFLD assessed by CT, in addition to CACS and FRS, could be useful for identifying T2DM patients at higher risk of cardiovascular events.

Efficacy of computed tomography features in the differentiation of basal cell adenoma and Warthin tumor in the parotid gland

The aim of this study was to identify computed tomography (CT) features that differentiate basal cell adenoma (BCA) from Warthin tumor (WT). Histopathologically confirmed parotid gland tumors (57 BCAs and 83 WTs) were retrospectively reviewed. CT images were evaluated to determine location, distribution, cyst formation, size, the new vessel facing sign (VFS), and enhancement behavior including the CT attenuation of solid portions of the tumor (AST), the vessel near the tumor (AVT), and maxillary artery (AMA) on early stage 2-phase contrast CT. Tumor CT attenuation ratios (AST/AVT and AST/AMA) were calculated. Chi-square tests, independent t-tests, and receiver operating characteristic curve analysis were conducted. Male:female ratio, patient age, posteroinferior location, tumor size, and presence of VFS were significantly lower for BCA than WT. The average AST/AVT was significantly higher for BCA than WT. The threshold value for AST/AVT on early stage 2-phase contrast CT was 0.72 between BCA and WT, and sensitivity and specificity were 94.7% and 98.8%, respectively, as calculated by receiver operating characteristic analysis. Gender ratio, age, location, size, presence of VFS, and AST/AVT value may help to differentiate BCA from WT in parotid glands on CT examination.

The classification of renal stones by gratings-based dark-field radiography.

IntroductionOccurrence of urinary calculi is a common medical condition. Since treatment and prevention measures depend on the type of stone found, reliable diagnostic tools are required. Dual energy computed tomography (CT) allows for rough classification of the stones found. After extraction, stone composition can be confirmed by laboratory analysis.We investigated to which degree gratings-based X-ray interferometry, which can measure attenuation, refraction and scattering (dark-field) properties of samples, allows for the discrimination of urinary stone type by calculating the ratio (R) of attenuation and scattering signals.Material and methodsIn an experimental setup we investigated 322 renal stone fragments from 96 patients which were extracted during routine clinical practice. Laboratory analysis showed the chemical composition of the urinary stones.These were correlated with dark field analysis of the stone samples. Measurements were performed on a X-rays gratings interferometer prototype. The attenuation, refraction and scattering signals were measured and the R-value calculated.ResultsThe spread of R-values of a given type of calculi is large, reducing the specificity of the method. Only uric acid stones can reliably be distinguished (sensitivity of 0.86 at a specificity of 0.9) from the other stones.ConclusionsGratings-based dark-field imaging is a non-destructive and potentially non-invasive technique that allows to discriminate between uric acid and non-uric acid stones, which from a clinical point of view represents by far the most important question for stone treatment.

ALMA detection of the dusty object silhouetted against the S0 galaxy NGC 3269 in the Antlia cluster

Context. An intriguing silhouette of a small dust patch can be seen against the disk of the S0 galaxy NGC 3269 in the Antlia cluster in optical images. The images do not provide any clue as to whether the patch is a local Jupiter mass-scale cloudlet or a large extragalactic dust complex. Aims. We aim to resolve the nature of this object: is it a small Galactic cloudlet or an extragalactic dust complex? Methods. ALMA and APEX spectroscopy and Gemini GMOS long-slit spectroscopy were used to measure the velocity of the patch and the NGC 3269 disk radial velocity curve. Results. A weak 16 ± 2.5 km s−1 wide 12CO(2 − 1) TMB 19 ± 2.5. mK line in a 2.″2 by 2.″12 beam associated with the object was detected with ALMA. The observed heliocentric velocity, Vr, hel = 3878 ± 5.0 km s−1, immediately establishes the extragalactic nature of the object. The patch velocity is consistent with the velocity of the nucleus of NGC 3269, but not with the radial velocity of the NGC 3269 disk of the galaxy at its position. The ∼4″ angular size of the patch corresponds to a linear size of ∼1 kpc at the galaxy’s Hubble distance of 50.7 Mpc. The mass estimated from the 12CO(2 − 1) emission is ∼1.4 × 106(d/50.7 Mpc)2 M⊙, while the attenuation derived from the optical spectrum implies a dust mass of ∼2.6 × 104(d/50.7 Mpc)2 M⊙. The derived attenuation ratio A′B/(A′B − A′R) of 1.6 ± 0.11 is substantially lower than the corresponding value for the mean Milky Way extinction curve for point sources (2.3). Conclusions. We established the extragalactic nature of the patch, but its origin remains elusive. One possibility is that the dust patch is left over from the removal of interstellar matter in NGC 3269 through the interaction with its neighbour, NGC 3268.

Life's Simple 7 and Nonalcoholic Fatty Liver Disease: The Multiethnic Study of Atherosclerosis

BackgroundThe American Heart Association (AHA) has defined Life's Simple 7 (LS7) as a measure of overall cardiovascular health . Nonalcoholic fatty liver disease (NAFLD) has been involved as a risk factor for cardiovascular disease. We evaluated the association between LS7 and NAFLD. MethodsWe evaluated participants form the Multi-Ethnic Study of Atherosclerosis (MESA) cohort. Cardiovascular health score was calculated from the Life's Simple 7 metrics. A score of 0-8 was considered inadequate, 9-10 average, and 11-14 optimal. NAFLD was defined using noncontrast cardiac computed tomography (CT) and a liver/spleen attenuation ratio (L/S) < 1. Multivariable regression were performed to evaluate the association. ResultsOur cross-sectional analysis of 3901 participants showed 19% (n = 747) had optimal cardiovascular health, 33% (n = 1270) had average, and 48% (n = 1884) had inadequate. White participants were most likely to have an optimal score (51%, n = 378), whereas African American participants had the lowest proportion with optimal scores (16%, n = 120; P < 0.001). The overall prevalence of NAFLD was 18% with a distribution of 7%, 14%, and 25% in the optimal, average, and inadequate score categories, respectively (P < 0.001). Adjusted for risk factors, average and optimal health categories had lower odds of NAFLD compared to those with inadequate scores: odds ratio for average, 0.44 (95% confidence interval 0.36-0.54); optimal, odds ratio 0.19 (95% confidence interval 0.14-0.26). This association was similar across gender, race and age groups. ConclusionA more favorable cardiovascular health score was associated with a lower prevalence of NAFLD. This study may suggest a potential of Life's Simple 7 in the prevention of liver disease.

Energy-aware scheduling in edge computing with a clustering method

With the development of Cloud and 5G technology, edge devices have been widely used in various areas. However, the limited battery energy and processing ability of edge devices hinder the usage scope of those devices. Prior studies have typically managed to immigrate virtual machines (VMs) or offload tasks to reduce energy consumption and shorten execution time. In our work, we consider devices that can obtain energy from a green energy source (such as wind energy, or solar energy). First, we use a clustering method to divide nodes into some clusters, each with some edge nodes to ensure the clusters have a minimum distance (defined by energy transferring attenuation ratios between nodes) between nodes in the cluster; the cluster center is a node with a VM. Then, based on the clustering method, a scheduling heuristic is proposed to transfer energy, immigrate VM, and allocate tasks. The simulation result shows that our proposed method reduces both the total energy consumption and the energy consumption from outside of the system (ECFO).

A metal-ceramic-rubber composite for hybrid gamma and neutron radiation shielding

In this study, silicone rubber (polydimethylsiloxane) matrix was incorporated with bismuth (III) oxide and hexagonal boron nitride (hBN) functional fillers to develop a flexible composite material that can shield both neutron and X/gamma radiations. Bismuth, as having a high atomic element weight is a very effective material for X/gamma electromagnetic radiation shielding, while hBN has a very high neutron cross-section due to its boron and nitrogen contents. On the other hand, the matrix material that is high temperature vulcanized (HTV) silicone rubber has superior properties of good flexibility, high transparency, and mechanical properties. Hexagonal boron nitride has unique properties and has a similar structure with graphite that is used for neutron moderation. Mechanical test results showed that the elastic modulus of the optimum sample has improved 4 times compared to control sample. Thermal, X ray and neutron attenuation tests were carried out for the developed composite materials. The curing behaviour was investigated in detail using Moving Die Rheometer. Kinetic studies of the vulcanization process were carried out in a very detailed way and high regression values up to 0.98 has been achieved. Non-destructive radiography images were taken to investigate the particle distribution and radiation attenuation of the prepared composites. It was seen that the composite material developed has a considerable attenuation ratio for both neutron and X/gamma radiations. X-ray attenuation test results for silicone rubber containing 20% Bi2O3 and 20% hBN with thickness of 6.4 mm were shown that the intensity of the incoming rays attenuated by 84.1%. Metal-ceramic-rubber composite material with 6.6 mm thickness shielded 65.8% of incoming neutrons.

Electromagnetic absorption efficiency of aluminum doped composite materials recycled from waste Tetra Pak packages in the frequency range 1.8 GHz to 5 GHz

Electromagnetic interference produced by high-speed electrical and electronic systems (i.e., base stations, mobile phones, radar, television and radio transmitters) that facilitate daily life also caused a pollution to be dealtwith as a part of daily life. Increasing use of electronic devices arising from the rapid developments in science and technology increased electromagnetic interference in electronic devices well besides the electromagnetic pollution in the environment. Therefore, there is a tremendous need to develop effective protection against the negative effects of electromagnetic interference. The objective of this paper is to make the composite boards from the recycling of Tetra Pak packages and to investigate the effect of aluminum additive on absorption efficiency of electromagnetic interference at various frequencies. Experimental results showed that as the ratio of aluminum additive rate in the composite material increased, the attenuation ratio increased.

Effect of plasma plume produced by vacuum laser welding on energy transmission

The correlation between plasma plume and laser energy transmission during vacuum laser welding of aluminum alloy was discussed in this study. The electron temperature and density of the plasma plume were calculated by spectroscopic analysis. The refraction and attenuation of laser energy were studied with a probe laser. The scattering effect of nanoparticles in the plasma plume on laser energy was studied. The influence of plasma plume on laser energy transmission mainly includes two ways: the changes in the area and location of the laser spot caused by laser refraction and the attenuation of laser energy mainly affected by inverse bremsstrahlung absorption and scattering. It was found that all these factors were sensitive to ambient pressure and decreased with the decrease of ambient pressure. For the refraction effect, the average area of laser and center position deflection angles were subject to a decrease as the ambient pressure decreased. When ambient pressure was 105 Pa, the average area and center position deflection angle of the laser was 5.48 mm2 and 1.22 mrad. While they would reduce to 3.12 mm2 and 0.118 mrad when ambient pressure was declined to 101 Pa. When the ambient pressures decreased from 105 Pa to 101 Pa, the attenuation ratio of the laser energy would reduce from 13.5% to 0.1% which had a great relationship with the plasma plume. For the inverse bremsstrahlung absorption effect, when the ambient pressure was 105 Pa, an 8.3% attenuation ratio of laser energy loss was produced while it would decrease to 0.027% with a further decrease of ambient pressure to 103 Pa. For the scattering effect, it was mainly determined by the size of the generated nanoparticles during welding. When ambient pressure dropped from 105 Pa to 101 Pa, the average diameter of nanoparticle also declined from 100 nm to 27 nm, reducing the attenuation ratio to decrease from 2.8% to 0.001%. The main attenuated mechanism of plasma plume to laser energy was inverse bremsstrahlung absorption when the ambient pressure was 105 Pa to 103 Pa while it was caused by other reasons under a lower ambient which a further investigation was needed.

Abstract 16796: Machine Learning-Based Hepatic Fat Assessment in Low-Dose Coronary Artery Calcium Scans is Correlated With Human Reader Assessment

Introduction: Hepatic attenuation on computed tomography (CT) is a surrogate marker for cardiometabolic risk, including Type 2 diabetes and its progression. Coronary artery calcium (CAC) screening for assessment of cardiovascular risk often includes portions of the liver and provides an opportunity for concomitant assessment of liver fat. However, the use of lower radiation dose CT and the need for reliable regions of interest (ROI) tracing creates challenges for routine clinical utilization. We present machine learning-based hepatic fat assessment (a) segmentation of liver and spleen and (b) CT attenuation measurement on low dose CT scans performed for CAC screening. Methods: Our approach (Figure 1a) comprises two steps. First, a deep learning-based model is utilized to segment the liver and spleen. Second, CT attenuation is measured on imaged organ volume. The segmentation model (U-Net with an EfficientNetB3 backbone) is trained with 5-fold cross-validation on 35 patients enrolled in the CLARIFY registry (clinicaltrials.gov NCT04075162) and validated on an independent set of 21 patients. The ground truth for segmentation is generated using Slicer 3D. Further, mean liver and mean liver-to-spleen CT attenuation is automatically measured on these scans and compared with manual ROI based assessment. Results: The segmentation model achieved a dice coefficient of 0.91 on the validation (Figure 1b). The automated volumetric assessment of liver and liver-to-spleen attenuation estimation showed a strong correlation with manual ROI assessment (Pearson correlation coefficient R=0.89 and R=0.88, respectively; Figure 1c). Conclusions: The presented machine-learning-based methods enable accurate estimation of liver and liver-to-spleen attenuation ratio on low-dose CAC CT scans. The approach needs to be further validated on larger, multi-institutional datasets to analyze its generalizability for hepatic fat assessment.

Liver segmental volume and attenuation ratio (LSVAR) on portal venous CT scans improves the detection of clinically significant liver fibrosis compared to liver segmental volume ratio (LSVR)

BackgroundThe aim of this proof-of-concept study was to show that the liver segmental volume and attenuation ratio (LSVAR) improves the detection of significant liver fibrosis on portal venous CT scans by adding the liver vein to cava attenuation (LVCA) to the liver segmental volume ratio (LSVR).Material and methodsPatients who underwent portal venous phase abdominal CT scans and MR elastography (reference standard) within 3 months between 02/2016 and 05/2017 were included. The LSVAR was calculated on portal venous CT scans as LSVR*LVCA, while the LSVR represented the volume ratio between Couinaud segments I-III and IV-VIII, and the LVCA represented the density of the liver veins compared to the density in the vena cava. The LSVAR and LSVR were compared between patients with and without significantly elevated liver stiffness (based on a cutoff value of 3.5 kPa) using the Mann–Whitney U test and ROC curve analysis.ResultsThe LSVR and LSVAR allowed significant differentiation between patients with (n = 19) and without (n = 122) significantly elevated liver stiffness (p < 0.001). However, the LSVAR showed a higher area under the curve (AUC = 0.96) than the LSVR (AUC = 0.74). The optimal cutoff value was 0.34 for the LSVR, which detected clinically increased liver stiffness with a sensitivity of 53% and a specificity of 88%. With a cutoff value of 0.67 for the LSVAR, the sensitivity increased to 95% while maintaining a specificity of 89%.ConclusionThe LSVAR improves the detection of significant liver fibrosis on portal venous CT scans compared to the LSVR.

Enhanced electrocatalytic activity and antifouling performance by iron phthalocyanine doped filtration membrane cathode

Use of iron phthalocyanine (FePc) filtration membrane cathode in microbial fuel cell (MFC) is a promising method to simultaneously improve electrocatalytic activity and antifouling performance. The filtration membrane cathode with the optimal content of 0.07 g FePc (FePc-7) exhibited the best oxygen reduction reaction (ORR) activity with the highest current density (12.0 A m−2) and the lowest charge transfer impedance (4.1 ± 0.4 Ω), which was 99% higher and 69% lower than the control (12.0 A m−2 and 4.1 ± 0.4 Ω). Besides, the FePc-7 had the largest transferred electrons (n = 3.97), indicating that the ORR occurred through a direct 4e− transfer pathway. The foregoing could be attributed to the Fe-Nx structure of FePc to form more energetically catalytic active sites, which could greatly increase the onset potential and reduce the adsorption energy of O2. The addition of FePc has remarkably increased the COD removal ratio and the FePc-7 showed the minimum effluent COD concentration of 21.7 ± 1.2 mg L−1, which was decreased by 61% compared to the control. Moreover, the antifouling performance was also a key factor maintaining excellent electrocatalytic activity and the FePc-7 + E (E was electric field) obtained the lowest flux attenuation ratio of 12.9 ± 0.3% with the thinnest fouling thickness of 55–60 μm, which was decreased by 47% than the control + E. The FePc filtration membrane cathode exhibited outstanding antifouling performance due to its superior hydrophilicity and stronger electrostatic repulsion force under electric field. This work provided an easy and facile modification method for the development of high-performance filtration membrane cathode in the MFC.