Low Attenuation Research Articles

Use of Photon-Counting Detector CT to Visualize Liver-Specific Gadolinium-Based Contrast Agents: A Phantom Study.

Background: The low clinically approved doses of gadolinium-based contrast agents (GBCA) do not generate sufficient enhancement on CT for diagnostic purposes. Photon-counting detector (PCD) CT offers improved spectral resolution and could potentially enable visualization of hepatocyte-specific GBCA given their associated high gadolinium concentrations within hepatocytes. Objective: To investigate the potential of gadoxetate disodium in combination with PCD CT and low-keV VMI reconstructions to achieve an increase in attenuation in a phantom. Methods: A series of solutions was prepared of diluted gadoxetate disodium (concentrations of 0.250-2.5 μmol/ml, corresponding with doses of 25-200 μmol/kg, respectively). These solutions, along with deionized water, were evaluated in an anthropomorphic abdominal phantom using a clinical PCD-CT scanner; virtual monoenergetic images (VMI) at 40, 50, 60, and 70 keV, along with virtual noncontrast (VMC) images, were generated. Attenuation measurements were obtained; a linear regression model combined these values with previously reported in vivo data to estimate hepatic enhancement and CNR across doses. Results: Attenuation increased with increasing concentration at a given energy level and with decreasing energy level for a given concentration; VNC images had lowest attenuation. The maximum attenuation reached was 45.2 HU for a concentration of 2.5 μmol/ml at 40 keV. A concentration of 0.25 μmol/ml had attenuation at 40 keV of 13.0 HU. The model yielded estimated in vivo hepatic enhancement at 40 keV of 4.9 HU for a dose of 25 μmol/kg, 19.9 HU for 100 μmol/kg, and 30.8 HU for 200 μmol/kg; corresponding CNRs were 0.13, 0.52, and 0.81, respectively. Conclusion: The combination of gadoxetate disodium and PCD CT could theoretically allow appreciable hepatic enhancement at a 200-μmol/kg dose; such effect was not observed for the clinically approved 25 μmol/kg dose. Clinical Impact: PCD CT achieved attenuation increases for gadoxetate disodium at considerably lower doses than previously documented for CT of GBCA, albeit approximately 8-times greater than clinical doses and thus too high for clinical use. Additional research exploiting PCD-CT technology could seek to reduce further doses required for sufficient visualization into a clinically feasible range, to potentially allow CT using a liver-specific agent.

Comparison of optical features in nitrobenzene-core PCF with hexagonal and square lattices in the claddings

This paper proposes two novel photonic crystal fibers (PCFs) with a nitrobenzene core, designed using hexagonal and square lattice structures. The characteristics of the PCFs were numerically analyzed in detail and compared to selecting the proposed optimal structure for supercontinuum generation. This study investigates the influence of core diameter (DC) on the characteristics of PCF. The fiber’s nonlinear properties are significantly enhanced by varying the core diameter. The hexagonal PCF structures provide flatter dispersion curves and are closer to zero dispersion than the square lattice, which is beneficial for supercontinuum generation. In contrast, the square PCF structures show higher nonlinear coefficients and lower attenuation than the corresponding hexagonal structures. Based on the simulation results, six optimized structures with all-normal and anomalous dispersion were selected to study the characteristics at the pump wavelength. Results indicate that the proposed PCFs exhibit near-zero flat dispersion, low attenuation and high nonlinearity. The selected optimal structures show potential for efficient supercontinuum generation, enabling broad and highly coherent spectra.

Expiration CT Gas Trapping Measures with Texture-Based Radiomics Improves Association with Lung Function and Lung Function Decline in COPD.

Several methods quantify gas-trapping on expiration computed tomography (CT) images, but they do not consider the spatial relationship of voxels. The objective of this study was to determine if the addition of expiration CT texture-based radiomics features to existing gas-trapping measurements improves model performance for lung function, lung function decline, COPD classification and visual gas-trapping. CanCOLD participants performed spirometry, plethysmography and CT chest imaging at full-inspiration/expiration with radiologist-assessed gas-trapping. Quantitative CT measurements were performed: low attenuation areas≤-856HU (LAA856), ratio of expiratory-to-inspiratory mean lung attenuation (E/I MLA), and difference between expiratory-inspiratory lung volumes between -856 and -950 HU (RVC856-950). Texture-based radiomics analysis generated 95 features; LASSO regression coefficients were summed to create a representative variable (RadScore). Multivariable linear regression models determined associations for baseline RV/TLC, FEV1/FVC, FEV1, FEF25-75, and 6-year ΔFEV1, with established CT gas-trapping and RadScore. Binary logistic regression determined associations for COPD classification and visual gas-trapping. 1111 participants were investigated (n=234 never-smokers, n=325 at-risk, n=314 mild COPD, n=238 moderate-severe COPD). In separate models for baseline RV/TLC, FEV1/FVC, FEV1, and FEF25-75, ΔFEV1, COPD classification and visual gas-trapping, all CT gas-trapping and CT RadScore measurements were independently significant (p<0.05). When CT gas-trapping and CT RadScore were included in the same model, all model performance metrics improved significantly (p<0.05). CT measures extracted from full-expiratory images that quantify the distribution, not just extent, of gas-trapping provide important information related to lung function and lung function decline in COPD. Full-expiratory CT texture-based radiomics improves model performance when used in combination with conventional gas-trapping measurements for lung function and lung function decline, COPD classification and presence of visual gas-trapping.

Calibration correction to improve registration during cone-beam CT guided histotripsy.

Histotripsy is a non-invasive, non-ionizing, non-thermal focused ultrasound technique. High amplitude short acoustic pulses converge to create high negative pressures that cavitate endogenous gas into a bubble cloud leading to mechanical tissue destruction. In the United States, histotripsy is approved to treat liver tumors under diagnostic ultrasound guidance but in initial clinical cases, some areas of the liver have not been treated due to bone or gas obstructing the acoustic window for targeting. To address this limitation in visualization, cone-beam computed tomography (CBCT) guided histotripsy was developed to expand the number of tumors and patients that can be treated with histotripsy. The purpose of this work is to improve the accuracy of CBCT guided histotripsy by calibrating the therapeutic bubble cloud location relative to the histotripsy robot arm. The calibration correction involves creating a bubble cloud sized treatment (a few mm) in an agar-based phantom consisting of 11 layers with alternating high and low x-ray attenuation. The layers were spaced ∼3mm apart to allow visualization of mixing after mechanical disintegration from the histotripsy treatment. Bubble cloud treatments were localized using an automated algorithm that minimized a cost function based on the intensity difference within the treatment region on the pre- and post-treatment CBCT. The actual treatment location can be compared to the theoretical bubble cloud location (focal point based on the CAD model of the transducer assembly) to calculate a 3D offset (X, Y, Z), which is used as the calibration correction between the therapeutic bubble cloud location and the histotripsy robot arm. The phantom and algorithm were analyzed to determine parameters that maximized bubble cloud treatment detection (treatment duration, localization accuracy of the phantom, number of bubble clouds) and were tested on four different histotripsy transducers. Bubble cloud locations were accurately identified with the automated algorithm from post-treatment CBCT images of the multilayer agar phantom. Treating the phantom for 20seconds was associated with the greatest change in CBCT intensity. The phantom and algorithm were able to localize changes in bubble cloud location with mean residual errors (MRE) between the measured and planned translations of 0.3±0.3mm in X, -0.2±0.6mm in Y, and 0.1±1.0mm in Z. A multi-bubble cloud calibration approach with four adjacent bubble clouds provided a statistically significant lower mean absolute deviation (MAD) in measured 3D offset (0.1, 0.0 and 0.2mm in X, Y, and Z, respectively) compared to using a single bubble cloud (MAD of 0.2, 1.1 and 1.2mm in X, Y, and Z, respectively). The calibration correction method measured statistically significantly different 3D transducer offsets between the four histotripsy transducers. Creating and analyzing four adjacent bubble clouds together produced more accurate and reproducible 3D offset measurements than analyzing individual bubble clouds. The presented histotripsy bubble cloud calibration correction method is automated, accurate, and can be easily integrated in the current histotripsy workflow to improve accuracy of CBCT guided histotripsy.

Experimental study and field application of hydraulic flushing technology in soft coal seam

To enhance the safety of coal mining operations and improve the efficiency of gas extraction, hydraulic flushing technology has been widely used in low permeability coal seams. This study aims to investigate the mechanism of hydraulic flushing by conducting experiments focusing on four aspects: sample strength, punching pressure, punching position and vibration direction. The results show that an increase in hydraulic flushing pressure leads to a deeper impact groove, whereas higher sample strength results in a shallower groove. Additionally, the amplitude of stress wave is positively correlated with the density of the sample, with low-strength samples exhibiting extensive stress wave propagation and minimal attenuation. The stress wave vibration is multi-directional, which can maximize the instability and destruction of the internal structure of the coal body. To validate the practical efficacy of hydraulic flushing, a field test was conducted at the Yuwu Coal Mine in Changzhi City, Shanxi Province. The field trial shows that the effective influence radius of hydraulic flushing can reach 4 m, with a significantly lower gas flow attenuation coefficient compared to ordinary borehole. Notably, the permeability of coal seam in hydraulic flushing area is close to twice that of ordinary drilling area.

Global 3D model of mantle attenuation using seismic normal modes.

Seismic tomographic models based only on wave velocities have limited ability to distinguish between a thermal or compositional origin for Earth's 3D structure1. Complementing wave velocities with attenuation observations can make that distinction, which is fundamental for understanding mantle convection evolution. However, global 3D attenuation models are only available for the upper mantle at present2-5. Here we present a 3D global model of attenuation for the whole mantle made using whole-Earth oscillations, constraining even spherical harmonics up to degree four. In the upper mantle, we find that high attenuation correlates with low velocity, indicating a thermal origin, in agreement with previous studies6,7. In the lower mantle, we find the opposite and observe the highest attenuation in the 'ring around the Pacific', which is seismically fast, and the lowest attenuation in the large low-seismic-velocity provinces (LLSVPs). Comparing our model with wave speeds and attenuation predicted by a laboratory-based viscoelastic model8 suggests that the circum-Pacific is acolder and small-grain-size region9, surrounding the warmer and large-grain-size LLSVPs. Viscosities calculated for the inferred variations in grain size and temperature confirm LLSVPs as long-lived, stable features10.

Analysis of Factors Affecting Prolonged Air Leak and Expansion Failure in the Lung after Resection in Patients with Pulmonary Malignancy and Predictive Value of Preoperative Quantitative Chest Computed Tomography.

The factors affecting the prolonged air leak (PAL) and expansion failure in the lung in patients undergoing resection for lung malignancy were analyzed. In this context, the value of the percentage of low attenuation area (LAA%) measured on preoperative quantitative chest computed tomography (Q-: CT) in predicting the development of postoperative PAL and the expansion time of the remaining lung (ET) in patients undergoing resection for lung malignancy was investigated. The data of 202 cases who underwent lung resection between July 2020 and December 2022 were analyzed. The factors affecting the development of PAL and ET were investigated using univariate and multivariate analyses. The cut-off value for LAA% was determined and its relationship with postoperative results was examined. In univariate analyses, for PAL, age (p = 0.022), presence of chronic obstructive pulmonary disease (COPD; p < 0.001), body mass index (BMI; p = 0.006), FEV1 (p = 0.020), FEV1/FVC (p < 0.001), LAA% (p = 0.008), diagnosis (p = 0.007), and surgical procedure (p < 0.001); for ET, diagnosis (p < 0.001) and surgical procedure (p = 0.001) were significant factors. A negative correlation between ET and BMI and FEV1/FVC (p < 0.01) and a positive correlation (p < 0.05) was detected with LAA%. The cut-off value for LAA% was calculated as 1.065. Multivariate analyses showed that the probability of developing PAL, increased 3.17-, 7.68-, and 3.08-fold in patients with COPD, lobectomy, and those above the cut-off value for LAA%, respectively (p = 0.045, p < 0.001, and p = 0.011). In addition, FEV1/FVC (p = 0.027), BMI (p = 0.016), and surgical procedure (p = 0.001) were shown to be independent factors affecting ET. Our study revealed the factors affecting PAL and expansion failure in the lung. Within this scope, it was concluded that preoperative Q-CT may have an important role in predicting the development of PAL and ET in the postoperative period and that LAA% measurement is an effective, objective, and practical method for taking precautions against possible complications.

Impact of diabetes mellitus on coronary artery plaque characteristics and outcomes in the SCOT-HEART trial.

Diabetes mellitus is an established cardiovascular risk factor. We assessed the impact of diabetes mellitus on quantitative plaque and long-term outcomes in patients with and without diabetes mellitus in the Scottish COmputed Tomography of the HEART (SCOT-HEART) trial. Coronary artery calcium (CAC) was assessed on non-contrast computed tomography (CT). Coronary stenoses, visually assessed adverse plaque characteristics and quantitative plaque burdens (calcified, non-calcified, low attenuation and total, Autoplaque 2.5) were assessed on coronary CT angiography. Multivariable and survival analyses were performed. Images of 1769 patients were assessed (56​% male, 58​±​9 years). Diabetes mellitus was present in 196 (11​%) patients. Patients with diabetes mellitus had higher 10-year cardiovascular risk score (29 [interquartile range 21, 40] versus 15 [9, 21] %, p​<​0.001) and CAC score (71 [1, 447] versus 17 [0, 209] Agatston units, p​<​0.001), but were not more likely to have obstructive disease or visually assessed adverse plaque characteristics. Patients with diabetes mellitus had higher quantitatively assessed calcified, non-calcified, low attenuation and total plaque burdens. After adjustment for age and sex, diabetes mellitus was an independent predictor of calcified plaque burden (p​=​0.009), but not the other plaque types. During 8.7 [IQR 8, 9.6] years follow-up, diabetes mellitus was associated with an increased risk of fatal or non-fatal myocardial infarction, adjusted for age and sex (hazard ratio 1.85, 95​% confidence interval 1.09 to 3.17, p​=​0.024). Diabetes mellitus was an independent predictor of quantitatively assessed plaque burden, particularly calcified plaque, and was associated with an increased risk of myocardial infarction.

Predictive Value of Preoperative Peak Oxygen Uptake for Postoperative Pulmonary Complications in Lung Cancer Patients with Chronic Obstructive Pulmonary Disease: A Single-center Retrospective Cohort Study.

The relationship between preoperative peak oxygen uptake/weight (VO2/W) and postoperative pulmonary complications (PPC) in lobectomies, including video-assisted thoracoscopic surgery, remains unclear. Traditional pulmonary function tests are often unreliable in this group, necessitating alternative predictive methods. Therefore, this study aimed to clarify the predictive value of preoperative peak VO2/W for PPC and explore factors related to PPC in lung cancer patients with chronic obstructive pulmonary disease (COPD). This single-center retrospective cohort study included 40 patients with lung cancer complicated by COPD who underwent a preoperative cardiopulmonary exercise test between January 2017 and March 2024. Patients were divided into those with and without PPC (PPC and non-PPC groups, respectively). Clinical parameters such as surgical approach, pulmonary function, low attenuation area, and peak VO2/W were compared between the groups. The association between these parameters and PPC was analyzed using multivariate logistic regression. The preoperative % diffusing capacity of the lung for carbon monoxide (%DLCO) and peak VO2/W were significantly lower in the PPC group than in the non-PPC group (p<0.01 and p<0.001, respectively), while the ventilatory equivalent/ventilatory carbon dioxide (VE/VCO2) was significantly higher in the PPC group than in the non-PPC group (p<0.05). In the multivariate logistic analysis including the %DLCO, peak VO2/W, VE/VCO2, and forced expiratory volume in 1 second, only peak VO2/W was identified as a significant independent factor for predicting PPC. The area under the receiver operating characteristic curve of peak VO2/W to predict PPC was 0.93, with a cutoff value of 14.6 mL/min/kg, sensitivity of 78%, and specificity of 95%. This study revealed that peak VO2/W was the most important parameter for predicting PPC in lung cancer patients with COPD. Incorporating cardiopulmonary exercise tests into preoperative assessments could improve risk stratification and perioperative management, potentially reducing the incidence of PPC in this high-risk population.

Association of Lung Function With Visceral Adiposity and Skeletal Muscle Mass Considering Myosteatosis.

Changes in body composition, including loss of muscle mass and obesity, adversely affect lung function. What is the relationship between lung function, visceral adiposity, and skeletal muscle mass, considering myosteatosis measured using CT scans in middle-aged Korean adults? We reviewed 15,827 participants (9,237 men and 6,590 women) with a mean (SD) age of 52.5 (8.3) years who underwent comprehensive health examinations, including abdominal CT imaging and spirometry. Selected CT scans were segmented automatically to quantify total abdominal muscle area (TAMA), visceral fat area (VFA), and subcutaneous fat area. Muscle quality was assessed by categorizing TAMA into 3 regions based on CT scan density: good-quality muscle (normal-attenuation muscle area [NAMA]), fatty muscle (low attenuation muscle area), and intermuscular and intramuscular fat areas. Low lung function was defined as FVC %predicted and FEV1< 80%predicted. Standardized residuals for CT scan-derived measurements, adjusted for age and BMI using linear regression, were calculated and stratified into quartiles for lung function comparison. Multivariate logistic regression was used to analyze associations between low lung function and variables. NAMA was correlated positively with FVC and FEV1, whereas VFA was correlated negatively with both. In men, low FVC and FEV1 were associated significantly with lower NAMA and higher VFA. Among women with obesity (BMI≥ 25kg/m2), low FVC and FEV1 were associated significantly with higher VFA and lower NAMA (FVC only); among women without obesity, low FVC and FEV1 were associated negatively with NAMA. Lung function was associated significantly with visceral adiposity and skeletal muscle quality, which differed according to sex and BMI. Improving lung function may require tailored management, including reducing visceral fat, enhancing skeletal muscle quality based on CT scan-body composition analysis, or both.

JWST Early Release Science Program TEMPLATES: Targeting Extremely Magnified Panchromatic Lensed Arcs and Their Extended Star Formation

This paper gives an overview of Targeting Extremely Magnified Panchromatic Lensed Arcs and Their Extended Star formation (TEMPLATES), a JWST Early Release Science program that targeted four extremely bright, gravitationally lensed galaxies, two extremely dusty and two with low attenuation, as templates for galaxy evolution studies with JWST. TEMPLATES obtains a common set of spectral diagnostics for these 1.3 ≤ z ≤ 4.2 galaxies, in particular Hα, Paschen α, and the rest-frame optical and near-infrared continua. In addition, two of the four targets have JWST coverage of [O iii] 5007 Å and Hβ; the other two targets have JWST coverage of polycyclic aromatic hydrocarbon 3.3 μm and complementary Atacama Large Millimeter/submillimeter Array data covering the [C ii] 158 μm emission line. The science goals of TEMPLATES are to demonstrate attenuation-robust diagnostics of star formation, map the distribution of star formation, compare the young and old stellar populations, and measure the physical conditions of star formation and their spatial variation across the galaxies. In addition, TEMPLATES has the technical goal to establish best practices for the integral field units within the NIRSpec and MIRI instruments, both in terms of observing strategy and in terms of data reduction. The paper describes TEMPLATES’s observing program, scientific and technical goals, data reduction methods, and deliverables, including high-level data products and data reduction cookbooks.

Dual-layer dual-energy CT characterization of thrombus composition in acute pulmonary embolism and chronic thromboembolic pulmonary hypertension

AbstractTo evaluate dual-layer dual-energy computed tomography (dlDECT)-based characterization of thrombus composition for differentiation of acute pulmonary embolism (PE) and chronic thromboembolic pulmonary hypertension (CTEPH). This retrospective single center cohort study included 49 patients with acute PE and 33 patients with CTEPH who underwent CT pulmonary angiography on a dlDECT from 06/2016 to 06/2022. Conventional images), material specific images (virtual non-contrast [VNC], iodine density overlay [IDO], electron density [ED]), and virtual monoenergetic images (VMI50KeV) were analyzed. Regions-of-interest (ROIs) were manually placed in pulmonary artery thrombi, and morphological imaging characteristics for acute and chronic PE were assessed. Area under the receiver operating characteristics curve (AUC) of ROI measurements, morphological imaging features, and their combination in distinguishing between acute PE and CTEPH were evaluated. Compared to PE, thrombi in patients with CTEPH had lower attenuation on conventional images (Median [inter-quartile range]: 40 [35–47] HU vs 64 [52–83] HU) and VMI50keV reconstructions (59 [46–72] HU vs 101 [80–123] HU) as well as decreased iodine uptake (IDO: 0.5 [0.2–1.0] vs 1.2 [0.5–1.8]; p for all &lt; 0.001). Conventional images and VMI50keV reconstructions were the most accurate for differentiating between acute and chronic thrombi (conventional: AUC 0.92, 95% CI 0.86–0.98; VMI50keV: AUC 0.91, 95% CI 0.85–0.97). Main pulmonary artery (MPA) diameter combined with thrombus attenuation significantly increased the AUC compared to MPA diameter alone (p = 0.002 respectively). Thrombi in patients with CTEPH exhibit lower attenuation and reduced contrast enhancement. Analyzing attenuation in pulmonary thrombi may add diagnostic information to established morphological parameters in differentiating acute PE from CTEPH.

Coronary calcium score and emphysema extent on different CT radiation dose protocols in lung cancer screening.

To assess the consistency of automated measurements of coronary artery calcification (CAC) burden and emphysema extent on computed tomography (CT) images acquired with different radiation dose protocols in a lung cancer screening (LCS) population. The patient cohort comprised 361 consecutive screenees who underwent a low-dose CT (LDCT) scan and an ultra-low-dose CT (ULDCT) scan at an incident screening round. Exclusion criteria for CAC measurements were software failure and previous history of CVD, including coronary stenting, whereas for emphysema assessment, software failure only. CT images were retrospectively analyzed by a fully automated AI software for CAC scoring, using three predefined Agatston score categories (0-99, 100-399, and ≥ 400), and emphysema quantification, using the percentage of low attenuation areas (%LAA). Demographic and clinical data were obtained from the written questionnaire completed by each participant at the first visit. Agreement for CAC and %LAA categories was measured by the k-Cohen Index with Fleiss-Cohen weights (Kw) and Intraclass Correlation Coefficient (ICC) with 95% Confidence Interval (CI). An overlap of CAC strata was observed in 275/327 (84%) volunteers, with an almost perfect agreement (Kw = 0.86, 95% CI 0.82-0.90; ICC = 0.86, 95% CI 0.79-0.90), while an overlap of %LAA strata was found in 204/356 (57%) volunteers, with a moderate agreement (Kw = 0.57, 95% CI 0.51-0.63; ICC = 0.57, 95% CI 0.21-0.75). Automated CAC quantification on ULDCT seems feasible, showing similar results to those obtained on LDCT, while the quantification of emphysema tended to be overestimated on ULDCT images. Question Evidence demonstrating that coronary artery calcification and emphysema can be automatedly quantified on ultra-low-dose chest CT is still awaited. Findings Coronary artery calcification and emphysema measurements were similar among different CT radiation dose protocols; their automated quantification is feasible on ultra-low-dose CT. Clinical relevance Ultra-low-dose CT-based LCS might offer an opportunity to improve the secondary prevention of cardiovascular and respiratory diseases through automated quantification of both CAC burden and emphysema extent.

Investigation of electromagnetic wave propagation characteristics across various frequencies in porous media of goaf.

The reliable long-distance transmission of electromagnetic wave signals within goaf is fundamental for the implementation of wireless monitoring and early warning systems for goaf-related disasters. This paper establishes an experimental platform for electromagnetic wave signal transmission within goaf and develops a propagation model for electromagnetic waves in the porous media of goaf. The transmission characteristics of electromagnetic waves at various frequencies within the porous media environment of goaf are investigated through experimental and numerical simulation approaches. The results indicate that the received signal intensity of electromagnetic waves across different frequency bands diminishes with increasing propagation distance in the lossy environment of the goaf. Initially, the decay follows a logarithmic pattern, whereas, at later stages, the attenuation exhibits a gradual and smooth decrease. As the frequency increases, the initial attenuation amplitude of electromagnetic wave intensity rises; however, subsequent attenuation is largely unaffected by frequency, with the later attenuation rate being proportional to porosity. Electromagnetic waves at a frequency of 700 MHz exhibit a low attenuation coefficient under both experimental and simulated conditions, demonstrating superior stability and reliability. This frequency significantly enhances the overall performance of the communication system and is suitable for use as the operational frequency band in wireless sensor networks.

SONG FREQUENCY SHIFTS IN AN URBAN BIRD SPECIES OPTIMIZE ACOUSTIC TRANSMISSION INSIDE NOISY URBAN AREAS

In animal acoustic communication is necessary that signals arrive to the receiver with reduced degradation and attenuation for a better transmission of the message. The noise pollution resulting from anthropogenic activities in cities reduces efficiency and efficacy of acoustic communication. Some species respond to high levels of noise increasing the minimum frequency of their vocalizations to avoid noise masking, but this may affect how sounds transmit in the environment because sounds with higher frequencies experience greater levels of attenuation and degradation. Using a transmission experiment, we analyzed how minimum frequency shifts, affect the sound transmission properties of the song of the House Wren (Troglodytes aedon) in urban areas that differ in the level of anthropogenic noise. We broadcasted songs with minimum frequencies between 1.2-1.8 kHz and the same songs with a minimum frequencies increment artificially of one semitone, increasing minimum frequencies to 2.1-2.6 kHz, in high and low noise level territories at four distances. We quantified signal-to-noise ratio, tail-to-signal ratio, blur ratio, and excess attenuation. Our results showed that songs with frequencies low minimum frequencies in low noise territories transmit with higher signal-to-noise ratio, and lower blur ratio and excess attenuation at longer distances. Songs with increased minimum frequencies only showed higher signal-to-noise ratio in noisier territories at longer distances. These results support the hypothesis of producing frequency shift to increase the communication distance in noisier environments. This is the first experimental study that tests the effect of shifting frequency on acoustic communication transmission on bird territories with different noise levels.

Hepatic parenchymal hypoattenuation in dogs with diabetes mellitus on computed tomography consistent with hepatic steatosis.

Hypoattenuation of the liver, consistent with hepatic steatosis or lipidosis, has been reported in veterinary patients. In people, measuring CT hepatic attenuation is diagnostic for hepatic steatosis, and hypoattenuation of the liver is defined as absolute if less than 40HU or relative if the liver is 10HU less than the spleen. The purpose of this study is to describe hepatic parenchymal attenuation in dogs with diabetes mellitus with or without diabetic ketosis (DK) or diabetic ketoacidosis (DKA), using the above categorization for absolute and relative hypoattenuation, as with humans. We hypothesized dogs with DK or DKA were more likely to have hypoattenuating livers. Twenty-seven diabetic dogs were included; fifteen were categorized in Group 1 as without DK or DKA, six in Group 2 as DK, and six in Group 3 as DKA. In Group 3, four of six dogs had absolute and relative hypoattenuating livers. Three of these were visually hypoattenuating to the vasculature, with one having negative attenuation and a histopathologic diagnosis of severe hepatic lipidosis. In Group 2, four of six dogs had relative hypoattenuating livers. In Group 1, only one of 15 dogs had a relatively hypoattenuating liver. Groups 2 and 3 had significantly lower absolute liver attenuation than Group 1. Presumed hepatic steatosis was present on CT and was more common with DK or DKA. These findings may help provide hepatic sampling recommendations and alter patient prognosis. Further research is needed to establish absolute and relative liver attenuation in dogs with correlation to histopathology and patient outcome.

Characterising high-risk plaque on cardiac CT.

Coronary computed tomography angiography (CCTA) is a well-established and reliable non-invasive imaging modality that provides a comprehensive assessment of coronary artery anatomy and luminal stenosis due to atherosclerosis. Owing to advances in CCTA software and technology, the composition and morphology of coronary plaque can be accurately evaluated. Adverse features which identify plaque as being high-risk or 'vulnerable' can provide a personalised cardiovascular risk assessment over and above stenosis severity. High-risk plaque features on CCTA include spotty calcification, low attenuation plaque, positive remodelling and the napkin ring sign. However, it can be challenging to characterise high-risk plaque accurately on CCTA, and as such, education and experience are required. In this pictorial essay, a comprehensive visual guide to high-risk plaque features on CCTA is provided, with clear examples and challenging cases that highlight common pitfalls. It is important for expert readers to properly identify these features given their association with adverse outcomes and potential future implications on intensive goal-directed medical therapy.

The September 21, 2020 (Mw = 5.6) Bystraya Earthquake at the South-Western Flank of the Baikal Rift Zone: a Milestone in Macroseismology of Eastern Siberia

The article presents analysis of macroseismic data on the September 21, 2020 (Mw = 5.6) Bystraya earthquake, which occurred in the eastern part of the Tunka basins system on the southwestern flank of the Baikal rift zone. Macroseismic data were collected mainly through an Internet questionnaire posted on the website of the Baikal Branch of the Geophysical Survey, Russian Academy Sciences. A total of 3013 eyewitness responses were collected, which is currently an unprecedented number in the entire history of macroseismic observations in the Baikal region. In total, we collected data for 263 Intensity Data Points. The maximal shaking intensity (VI–VII MSK-64) was observed in the Bystraya village and the Kultuk settlement. The shaking intensity V MSK-64 was noted at a distance of up to ∼180 km; intensity IV MSK-64 was recorded at a distance of up to ∼550 km. Analysis of data on the Bystraya earthquake revealed significantly lower attenuation compared to that expected from the regional macroseismic equation. Due to the large volume of macroseismic data collected, as well as the high efficiency of the data collection method used, the Bystraya earthquake can be considered an important milestone in macroseismic research in East Siberia.

Necrotizing pneumonia-a rare but complex complication in bronchiectasis patients.

Pneumonia occurs commonly in bronchiectasis patients with exacerbation, though necrotizing pneumonia remains rare. This report presents two cases of bronchiectasis complicated by necrotizing pneumonia. The first case involves a 39-year-old female with bronchiectasis due to primary ciliary dyskinesia. She presented with severe chest pain and persistent fever unresponsive to oral antibiotics. Chest computed tomography (CT) revealed necrotizing pneumonia with associated empyema, necessitating prolonged antibiotic therapy, pleural drainage and ultimately surgical decortication. The second case is a 39-year-old male with bronchiectasis following ammonia inhalation injury, presenting with pleuritic chest pain and productive cough, with a CT scan showing consolidation with low attenuation areas. Intensive antibiotic treatment was required, alongside corticosteroids and inhaled antibiotics afterward. These cases demonstrate the importance of identifying risk factors for necrotizing pneumonia in bronchiectasis patients. Tailoring treatment strategies, including extending antibiotic regimens, using inhaled antibiotics, and administering corticosteroids, is essential to mitigate poor outcomes.

The influence of serum uric acid on coronary atherosclerosis plaque phenotypes by computed tomography angiography: The missing link?

The interaction of serum uric acid (SUA) with atherogenesis is incompletely understood. Aim of our study was to investigate the association of SUA levels with coronary plaque composition including high-risk-plaque (HRP) features by coronary computed tomography angiography (CTA) and for the prediction of major adverse cardiac events (MACE). 1242 patients (age 66.17±11.03; 56% males) referred to coronary CTA were included. SUA>6.5mg/dl was defined as hyperuricemia. CTA-image analysis included: Coronary stenosis severity (CADRADS), plaque burden (SIS/G-score weighted for non-calcifying plaque), plaques types (1=calcifying; 2=mixed (predominantly calcifying); 3=mixed (predominantly noncalcifying), 4=noncalcifying."High-risk-plaque"(HRP)-features were quantified: Low-attenuation plaque (LAP) density, Spotty calcification, Napkin-Ring Sign (NRS), Remodeling Index. Coronary Artery Calcium Score (CAC) was measured. Primary outcome was MACE. HRP-features were more prevalent in patients with hyperuricemia (p=0.005, p=0.0002, p=0.0004). SUA level was associated with LAP<30HU (HR:1.23; p=0.04). Plaque burden and CAC-score were higher in the hyperuricemia group (G-score:p=0.022 and CAC:p=0.027). After a mean follow-up of mean 8,32 years, MACE rate was 2.9%. There was no difference in the MACE rate between subjects with elevated SUA and normals (HR 1.221:95%CI:0.817-2.563; p=0.597). Low-attenuation-plaque density/LAP<30HU was the strongest prognosticator for MACE (p=0.033 and p=0.013); stenosis severity, plaque types and G-score were also predictive, but not SUA, CAC and the other conventional cardiovascular risk factors (except smoking). SUA is associated with HRP-features and coronary plaque burden. Low attenuation plaque is the strongest predictor of MACE, but not SUA level and other major CVRF. CTA imaging biomarkers may improve CV-risk stratification in patients with hyperuricemia.