Attenuation Values Research Articles

A lightweight and efficient hollow sunken carbon@MnO2/reduced graphene oxide composite for high-performance electromagnetic wave absorption

To address the environmental and health issues stemming from electromagnetic pollution, it is crucial to investigate high-performance and practical materials for absorbing electromagnetic waves. Herein, the ternary lightweight SC@MnO2/RGO (SCMR) composites are synthesized by using a special kind of hollow sunken carbon nanoparticles (SC) as a substrate and combining MnO2 nanosheets with 2D reduced graphene oxide (RGO). The investigation results show that the minimum reflection loss (RLmin) of SCMR3 can reach −60.95 dB with a matched thickness of 1.47 mm and a frequency of 13.12 GHz, and the effective absorption bandwidth (EAB) is 4.08 GHz (13.76–17.84 GHz) at the thickness of 1.23 mm. Its excellent performance comes from high dielectric loss capability, multiple reflections, interfacial polarization, and defective polarization relaxation brought by the structure of the composite, which can effectively enable electromagnetic wave absorption and facilitates energy conversion. Furthermore, simulation-based assessment under far-field conditions elucidates the radar stealth effect, demonstrating that the maximum radar cross-section (RCS) attenuation value of SCMR3-coated perfect electrical conductor (PEC) at Phi = 0° and θ = 0° can attain 32.13 dB m2. Ultimately, this study presents a viable design methodology for developing lightweight, efficient, and application-oriented carbon-based electromagnetic wave absorption materials.

Association between higher intermuscular adipose tissue and decreased renal function in patients with systemic lupus erythematosus mediated by insulin resistance

ObjectivesTo quantify the relationship between abdominal computed tomography (CT)-based body composition parameters and renal function in systemic lupus erythematosus (SLE) patients and evaluate the potential effect of insulin resistance on this relationship.MethodsSLE patients from institutions A and B between January 2017 and August 2023 were enrolled. Areas and attenuation values of subcutaneous adipose tissue, visceral adipose tissue, intermuscular adipose tissue (IMAT), and skeletal muscle index on CT images were measured at the L3 vertebral level. Logistic regression analysis was used to identify risk factors associated with decreased renal function. Linear regression models were used to describe the relationships between body composition parameters and estimated glomerular filtration rate (eGFR). Finally, we used a single-point insulin sensitivity estimator to indirectly reflect the degree of insulin resistance and assess its mediating effect on the association between IMAT area and decreased renal function.ResultsThree-hundred thirty-nine SLE patients from institution A (internal dataset) and 114 SLE patients from institution B (external validation dataset) were included. Multivariate logistic regression revealed that IMAT area (odds ratio (OR)institution A: 1.05 (95% confidence intervals (95% CI): 1.01, 1.10), and ORinstitution B: 1.19 (95% CI: 1.03, 1.39)) was an independent risk factor for decreased renal function in SLE patients. In the adjusted linear regression model, high IMAT area was significantly associated with reduced eGFR (βinstitution A = −1.15, Pinstitution A = 0.005; βinstitution B = −0.98, Pinstitution B = 0.049). Additionally, insulin resistance contributed a mediating role of 22.8% to the association.ConclusionHigh IMAT area was associated with decreased renal function in SLE patients and insulin resistance mediated this relationship.Critical relevance statementHigh intermuscular adipose tissue area is associated with decreased renal function in systemic lupus erythematosus patients mediated by insulin resistance and is correlated with chronicity index in lupus nephritis patients.Key PointsHigh intramuscular adipose tissue (IMAT) area was associated with decreased renal function in systemic lupus erythematosus (SLE) patients.Insulin resistance mediated the association between IMAT area and eGFR.IMAT area was associated with chronicity index in lupus nephritis patients.Graphical

Frequency-dependent shear wave attenuation across the Central Anatolia region, Türkiye

Abstract. The Central Anatolian Plateau with its volcanic provinces represents a broad transition zone between the compressional deformation in the east and the extensional regime in the west. The Central Anatolian Fault Zone separates the Kırşehir Block in the north and the Anatolide–Tauride Block in the south within the plateau. A proper understanding of physical properties such as seismic attenuation in the crustal volume of this region can provide hints toward the possible source for the geodynamic events in the past and present that likely lead to the observed deformation. In order to model intrinsic and scattering attenuation separately, we perform a nonempirical coda-wave modeling approach in which a fitting process between observed and synthetic coda-wave envelopes is performed for each earthquake in multiple frequency bands. Here, the acoustic radiative transfer theory, assuming multiple isotropic scattering, was utilized for the forward modeling of the synthetic coda-wave envelopes of local earthquakes. Our findings generally highlight the prominent nature of intrinsic attenuation over scattering attenuation, implying the presence of thick volcanic rocks with relatively high attenuation values beneath Central Anatolia. Overall, the spatial distribution of the attenuation at varying frequencies marks the Kırşehir Massif distinctively with its considerable high-attenuating character. Our findings, combined with early seismological and geo-electrical models, suggest a possible partial melt beneath most of the Central Anatolian Volcanic Province, and the resultant zones of elevated fluid-rich content exhibit high and dominant intrinsic attenuation. To the southeast, a gradual decrease in the observed attenuation coincides with the Central Taurus Mountains where high altitude is considered to be evolved following the slab break-off and resulting mantle upwelling.

Acoustic Effects of Uneven Polymeric Layers on Tunable SAW Oscillators

Surface acoustic wave (SAW) sensors in tunable oscillator configuration, with a deposited polymeric layer, were used to investigate the layer’s impact on the oscillator’s resonant frequency. The SAW oscillators were tuned by means of variable loop amplification. Full-range amplification variation led to a resonant frequency increase of ~1.7 MHz due to the layer’s nonlinear reaction. The layer’s morphology and location resulted in a specific resonant frequency–amplitude dependence. Five types of layers were used to test the causal linkage between the layers’ morphological parameters or positioning and the SAW oscillator’s resonant frequency. The frequency variation trend is almost linear, with a complex minute variation. Small amplitude sigmoids occur at certain attenuation values, due to layer acoustic resonances. Multiple sigmoids were linked with layer resonances of different orders. A good correlation between the layer’s thickness and resonance position was found.

Automated hepatic steatosis assessment on dual-energy CT-derived virtual non-contrast images through fully-automated 3D organ segmentation

PurposeTo evaluate the efficacy of volumetric CT attenuation-based parameters obtained through automated 3D organ segmentation on virtual non-contrast (VNC) images from dual-energy CT (DECT) for assessing hepatic steatosis.Materials and methodsThis retrospective study included living liver donor candidates having liver DECT and MRI-determined proton density fat fraction (PDFF) assessments. Employing a 3D deep learning algorithm, the liver and spleen were automatically segmented from VNC images (derived from contrast-enhanced DECT scans) and true non-contrast (TNC) images, respectively. Mean volumetric CT attenuation values of each segmented liver (L) and spleen (S) were measured, allowing for liver attenuation index (LAI) calculation, defined as L minus S. Agreements of VNC and TNC parameters for hepatic steatosis, i.e., L and LAI, were assessed using intraclass correlation coefficients (ICC). Correlations between VNC parameters and MRI-PDFF values were assessed using the Pearson’s correlation coefficient. Their performance to identify MRI-PDFF ≥ 5% and ≥ 10% was evaluated using receiver operating characteristic (ROC) curve analysis.ResultsOf 252 participants, 56 (22.2%) and 16 (6.3%) had hepatic steatosis with MRI-PDFF ≥ 5% and ≥ 10%, respectively. LVNC and LAIVNC showed excellent agreement with LTNC and LAITNC (ICC = 0.957 and 0.968) and significant correlations with MRI-PDFF values (r = − 0.585 and − 0.588, Ps < 0.001). LVNC and LAIVNC exhibited areas under the ROC curve of 0.795 and 0.806 for MRI-PDFF ≥ 5%; and 0.916 and 0.932, for MRI-PDFF ≥ 10%, respectively.ConclusionVolumetric CT attenuation-based parameters from VNC images generated by DECT, via automated 3D segmentation of the liver and spleen, have potential for opportunistic hepatic steatosis screening, as an alternative to TNC images.

Virtual noncontrast images reveal gouty tophi in contrast-enhanced dual-energy CT: a phantom study

BackgroundDual-energy computed tomography (DECT) is useful for detecting gouty tophi. While iodinated contrast media (ICM) might enhance the detection of monosodium urate crystals (MSU), higher iodine concentrations hamper their detection. Calculating virtual noncontrast (VNC) images might improve the detection of enhancing tophi. The aim of this study was to evaluate MSU detection with VNC images from DECT acquisitions in phantoms, compared against the results with standard DECT reconstructions.MethodsA grid-like and a biophantom with 25 suspensions containing different concentrations of ICM (0 to 2%) and MSU (0 to 50%) were scanned with sequential single-source DECT using an ascending order of tube current time product at 80 kVp (16.5–220 mAs) and 135 kVp (2.75–19.25 mAs). VNC images were equivalently reconstructed at 80 and 135 kVp. Two-material decomposition analysis for MSU detection was applied for the VNC and conventional CT images. MSU detection and attenuation values were compared in both modalities.ResultsFor 0, 0.25, 0.5, 1, and 2% ICM, the average detection indices (DIs) for all MSU concentrations (35–50%) with VNC postprocessing were respectively 25.2, 36.6, 30.9, 38.9, and 45.8% for the grid phantom scans and 11.7, 9.4, 5.5, 24.0, and 25.0% for the porcine phantom scans. In the conventional CT image group, the average DIs were respectively 35.4, 54.3, 45.4, 1.0, and 0.0% for the grid phantom and 19.4, 17.9, 3.0, 0.0, and 0.0% for the porcine phantom scans.ConclusionsVNC effectively reduces the suppression of information caused by high concentrations of ICM, thereby improving the detection of MSU.Relevance statementContrast-enhanced DECT alone may suffice for diagnosing gout without a native acquisition.Key points• Highly concentrated contrast media hinders monosodium urate crystal detection in CT imaging• Virtual noncontrast imaging redetects monosodium urate crystals in high-iodinated contrast media concentrations.• Contrast-enhanced DECT alone may suffice for diagnosing gout without a native acquisition.Graphical

IMPLEMENTATION OF AN EFFECTIVE FSO WDM SYSTEM UNDER DIFFERENT ATMOSPHERIC CONDITIONS WITH DIFFERENT CODING SCHEMES

In different atmospheric conditions, Free Space Optical (FSO) transmission is vital because it sends data via light beams through the atmosphere. This technique transmits data quickly and efficiently with low signal attenuation in clear weather. This makes it ideal for short- to medium-range communication, especially in urban areas where cables or radio frequency spectrum are impractical. However, fog, rain, and snow can absorb or disperse the light signal, reducing transmission range and reliability for FSO. This research creates an effective FSO system that supports many channels and transmission distances. The suggested system will be tested in four weather conditions (light air, light rain, medium rain, and heavy rain) with attenuation values of 0.47, 1.988, 5.844, and 9.29 dB/km. Optisystem program version 21 designs and evaluates system performance based on QF, BER, and other criteria. In this research, multiple modulation formats are evaluated for best performance. QF exhibited a reversal relationship with distance, while BER showed a direct one. The suggested system can transmit for 25 km, 12 km, 10 km, and less than 6 km in light air, light rain, medium rain, and severe rain. This research also examines system performance under NRZ and RZ modulation formats. NRZ modulation is better for light air and clear weather transmission than RZ modulation since it requires less equipment and is easier to install. Since NRZ modulation requires no clock recovery overhead, bandwidth efficiency is usually higher. In light rain, RZ modulation minimizes optical fiber dispersion, extending transmission distances and improving signal quality. NRZ excels within 10 kilometers. NRZ works for 6 km and 4 km in medium and severe rain, although RZ's dispersion tolerance and synchronization make it better for longer transmission distances. For short distances, NRZ is suitable, but for longer distances, RZ is more resilient due to its better dispersion management and signal transmission.

Post-contrast CT liver attenuation alone is superior to the liver-spleen difference for identifying moderate hepatic steatosis.

To assess the diagnostic performance of post-contrast CT for predicting moderate hepatic steatosis in an older adult cohort undergoing a uniform CT protocol, utilizing hepatic and splenic attenuation values. A total of 1676 adults (mean age, 68.4 ± 10.2 years; 1045M/631F) underwent a CT urothelial protocol that included unenhanced, portal venous, and 10-min delayed phases through the liver and spleen. Automated hepatosplenic segmentation for attenuation values (in HU) was performed using a validated deep-learning tool. Unenhanced liver attenuation < 40.0 HU, corresponding to > 15% MRI-based proton density fat, served as the reference standard for moderate steatosis. The prevalence of moderate or severe steatosis was 12.9% (216/1676). The diagnostic performance of portal venous liver HU in predicting moderate hepatic steatosis (AUROC = 0.943) was significantly better than the liver-spleen HU difference (AUROC = 0.814) (p < 0.001). Portal venous phase liver thresholds of 80 and 90 HU had a sensitivity/specificity for moderate steatosis of 85.6%/89.6%, and 94.9%/74.7%, respectively, whereas a liver-spleen difference of -40 HU and -10 HU had a sensitivity/specificity of 43.5%/90.0% and 92.1%/52.5%, respectively. Furthermore, livers with moderate-severe steatosis demonstrated significantly less post-contrast enhancement (mean, 35.7 HU vs 47.3 HU; p < 0.001). Moderate steatosis can be reliably diagnosed on standard portal venous phase CT using liver attenuation values alone. Consideration of splenic attenuation appears to add little value. Moderate steatosis not only has intrinsically lower pre-contrast liver attenuation values (< 40 HU), but also enhances less, typically resulting in post-contrast liver attenuation values of 80 HU or less. Moderate steatosis can be reliably diagnosed on post-contrast CT using liver attenuation values alone. Livers with at least moderate steatosis enhance less than those with mild or no steatosis, which combines with the lower intrinsic attenuation to improve detection. The liver-spleen attenuation difference is frequently utilized in routine practice but appears to have performance limitations. The liver-spleen attenuation difference is less effective than liver attenuation for moderate steatosis. Moderate and severe steatosis can be identified on standard portal venous phase CT using liver attenuation alone.

Accelerated fusion dynamics by recombinant human bone morphogenetic protein-2 following transforaminal lumbar interbody fusion, particularly in osteoporotic conditions

BACKGROUND CONTEXTEarly fusion is crucial in interbody procedures to minimize mechanical complications resulting from delayed union, especially for patients with osteoporosis. Bone morphogenetic proteins (BMPs) are used in spinal fusion procedures; however, limited evaluation exists regarding time-to-fusion for BMP use, particularly in patients with osteoporosis. PURPOSETo evaluate the difference in time-to-fusion after single-level transforaminal lumbar interbody fusion (TLIF) surgery between recombinant human bone morphogenetic protein-2 (rhBMP-2) usage and nonusage groups according to bone density. STUDY DESIGNRetrospective single-center cohort study. PATIENT SAMPLEThis study enrolled 132 patients (mean age, 65.25±8.66; male patients, 40.9%) who underwent single-level TLIF for degenerative disorders between February 2012 and December 2021, with pre and postoperative computed tomography (CT). OUTCOME MEASUREThe interbody fusion mass and bone graft status on postoperative CT scans was obtained annually, and time-to-fusion was recorded for each patient. METHODSThe patients were divided into 2 groups based on rhBMP-2 use during the interbody fusion procedure. Patients were further divided into osteoporosis, osteopenia, and normal groups based on preoperative L1 vertebral body attenuation values, using cutoffs of 90 and 120 Hounsfield units. It was strictly defined that fusion is considered complete when a trabecular bone bridge was formed, and therefore, the time-to-fusion was measured in years. Time-to-fusion was statistically compared between BMP group and non-BMP groups, followed by further comparison according to bone density. RESULTSThe time-to-fusion differed significantly between BMP and non-BMP groups, with half of the patients achieving fusion within 2.5 years in the BMP group compared with 4 years in the non-BMP group (p<.001). The fusion rate varied based on bone density, with the maximum difference observed in the osteoporosis group, when half of the patients achieved fusion within 3 years in the BMP group compared to 5 years in the non-BMP group (p<.001). Subgroup analysis was conducted, revealing no significant associations between time-to-fusion and factors known to influence the fusion process, including age, gender, medical history, smoking and alcohol use, and medication history, except for rh-BMP2 use and bone density. CONCLUSIONSRhBMP-2 usage significantly reduced time-to-fusion in single-level TLIF, especially in patients with osteoporosis. LEVEL OF EVIDENCELevel III.

Relationship between different clinical characteristics and pericoronary adipose tissue attenuation values quantified from coronary computed tomographic angiography (CCTA) in patients without coronary heart disease (CHD)

Relationship between different clinical characteristics and pericoronary adipose tissue attenuation values quantified from coronary computed tomographic angiography (CCTA) in patients without coronary heart disease (CHD)

Are transmembrane 6 superfamily member 2 gene polymorphisms associated with steatohepatitis after pancreaticoduodenectomy?

After pancreaticoduodenectomy, 20-40% of patients develop steatotic liver disease (SLD), and steatohepatitis can be a problem. Although patatin-like phospholipase domain-containing 3 protein (PNPLA3) and transmembrane 6 superfamily member 2 (TM6SF2) polymorphisms are involved in SLD and steatohepatitis development, whether this is the case after pancreaticoduodenectomy is unclear. Forty-three patients with pancreatic cancer who underwent pancreaticoduodenectomy at our hospital between April 1, 2018, and March 31, 2021, were included. We extracted DNA from noncancerous areas of residual specimens after pancreaticoduodenectomy and determined PNPLA3 and TM6SF2 gene polymorphisms using real-time polymerase chain reaction. SLD was defined as a liver with an attenuation value of ≤40 HU or a liver-to-spleen ratio of ≤0.9 on computed tomography. We defined high hepatic fibrosis indexes (HFI) instead of steatohepatitis as a Fibrosis-4 index of ≥2.67 or nonalcoholic fatty liver disease fibrosis score of ≥0.675 in patients with SLD. The cumulative incidence of SLD (P = 0.299) and high HFI (P = 0.987) after pancreaticoduodenectomy were not significantly different between the PNPLA3 homozygous and minor allele groups. The incidences of high HFI at 1 year after pancreaticoduodenectomy were 16.8% and 27.0% in the TM6SF2 major homozygous and minor allele groups, respectively, with a significant difference in the cumulative incidence (P = 0.046). The TM6SF2 minor allele may contribute to steatohepatitis development after pancreaticoduodenectomy.

Chest non‑contrasted computed tomography in detecting acute pulmonary thromboembolism: A single‑center retrospective study.

The object of the study was to evaluate comprehensively the value of chest non-contrasted CT (NC-CT) in detecting acute pulmonary thromboembolism (APE). All patients were categorized into two groups: i) With APE; and ii) without APE based on clinical diagnosis. Using the clot distribution on computed tomography pulmonary angiography (CTPA), APE was divided into central and peripheral APE. Imaging features including hyperdense lumen sign and peripheral wedge-shaped opacity on chest NC-CT were evaluated. The attenuation value of peripheral wedge-shaped opacity on NC-CT was compared between patients with and without APE. Among the 273 patients, there were 110 patients with APE, 49 patients with central APE and 61 patients with peripheral APE and 163 patients without APE. The hyperdense lumen sign had a sensitivity of 30.0% and a specificity of 97.6% in detecting APE. The sensitivity and specificity of hyperdense lumen sign in detecting central APE were 57.1 and 97.6%, respectively, while the relevant percentages in detecting peripheral APE were 8.2 and 97.6%, respectively. The mean attenuation value of peripheral wedge-shaped opacity in patients with APE was significantly lower than that in patients without APE (P<0.001). Regarding the age-adjusted D-dimer, there was a decrease of eight D-dimer positive cases for patients >50 years old without APE, confirmed by CTPA. In conclusion, chest NC-CT cannot be used as an alternative modality for CTPA in diagnosing APE, however, the hyperdense lumen sign had high specificity in the diagnosis of central APE. Patients with this symptom and increased D-dimer may not require further CTPA. The lower attenuation value of peripheral wedge-shaped opacity on NC-CT suggested APE, and CTPA confirmation was required. The age-adjusted D-dimer had higher specificity in excluding APE.

Correlation between Balthazar CT grading, CECT necrosis volume, attenuation value, and prognosis of patients with acute necrotizing pancreatitis.

To analyze the correlation between Balthazar CT grading and contrast-enhanced CT necrosis volume and attenuation value and prognosis of patients with acute necrotizing pancreatitis. Ninety-two patients with acute necrotizing pancreatitis who were treated in the hospital were selected between June 2019 and June 2021, and they were divided into the poor prognosis group and the good prognosis group according to the clinical prognosis at 6 months of follow-up. Balthazar CT, contrast-enhanced CT necrosis volume, and attenuation value were compared between the 2 groups. Multivariate logistic regression analysis was used to analyze the influencing factors. Receiver operating characteristic curve was adopted to analyze the predictive value. Among the 92 participants, there were 28 cases with good prognosis (30.43%) and 64 cases with poor prognosis (69.57%). The Acute Physiology and Chronic Health Evaluation II score, C-reactive protein, urea nitrogen, Balthazar CT, necrotic volume, and average attenuation value of the poor prognosis group were significantly higher than those of the good prognosis group (all P values <.05). The results of the multivariate logistic analysis showed that Balthazar CT grade, necrotic volume, and average attenuation value were independent risk factors for poor prognosis in patients with acute necrotizing pancreatitis (all P values <.05). The area under the curve of Balthazar CT grade, necrotic volume, average attenuation value, and the joint detection in predicting the prognosis of patients with acute necrotizing pancreatitis were 0.765, 0.624, 0.764, and 0.861, respectively. The Balthazar CT grading, necrosis volume, and average attenuation value are significantly higher among patients with acute necrotizing pancreatitis complicated with poor prognosis, and they are also independent risk factors for poor prognosis in patients with acute necrotizing pancreatitis, and can help clinically predict the prognosis of patients with acute necrotizing pancreatitis, and the combined detection has better application effects.

The Output Signal-to-Noise Ratio and Speech Perception in Noise: The Effect of Multichannel and Free-Channel Hearing Aids

Background and Aim: The output Signal-to-Noise Ratio (SNR) is one of the essential factors in hearing aid benefits. There is limited evidence regarding SNR improvement by the Channel-Free (CFHA) and Multi-Channel Hearing Aid (MCHA) and the speech understanding in noise through them. This study aimed to investigate the extent to which output SNR was modified by CFHA and MCHA processing and the variation in aided speech recognition abilities with a change in output SNR. Methods: Thirty-six participants aged 50–65 years were included. A chosen CFHA and MCHA were used to obtain the output SNR and sentence recognition in noise in four different processing algorithms (linear, linear+noise reduction, WDRC, WDRC+noise reduction). Hagerman’s phase inversion technique was used to measure the attenuation of noise and, in turn, to obtain the output SNR of the hearing aid. Results: In all hearing aid processing algorithms among those with normal hearing and people with hearing loss, the output of CFHA revealed higher attenuation values than that of MCHA. There was a significant effect of the hearing aids and processing algorithms in both normal and individuals with hearing impairment on the mean SNR. Further, multiple linear regression analysis results showed that whether the hearing is channel-free or multi- channel significantly predicted speech recognition scores, while output SNR and processing algorithms did not. Conclusion: The signal processing algorithms in CFHA had greater noise attenuation values, better output SNR, and speech recognition scores, showing an advantage over the modern MCHA among individuals with hearing impairment. Keywords: Channel-free hearing aids; multi-channel hearing aids; sensorineural hearing loss; speech recognition

Pulse-echo ultrasound attenuation tomography

Objective. We present the first fully two-dimensional attenuation imaging technique developed for pulse-echo ultrasound systems. Unlike state-of-the-art techniques, which use line-by-line acquisitions, our method uses steered emissions to constrain attenuation values at each location with multiple crossing wave paths, essential to resolve the spatial variations of this tissue property. Approach. At every location, we compute normalized cross-correlations between the beamformed images that are obtained from emissions at different steering angles. We demonstrate that their log-amplitudes provide the changes between attenuation-induced amplitude losses undergone by the different incident waves. This allows us to formulate a linear tomographic problem, which we efficiently solve via a Tikhonov-regularized least-squares approach. Main results. The performance of our tomography technique is first validated in numerical examples and then experimentally demonstrated in custom-made tissue-mimicking phantoms with inclusions of varying size, echogenicity, and attenuation. We show that this technique is particularly good at resolving lateral variations in tissue attenuation and remains accurate in media with varying echogenicity. Significance. Based on a similar principle, this method can be easily combined with computed ultrasound tomography in echo mode for speed-of-sound imaging, paving the way towards a multi-modal ultrasound tomography framework characterizing multiple acoustic tissue properties simultaneously.

Accurate calculation method of terrain viewshed for wireless signal as line of sight

AbstractViewshed analysis is an important research content of digital terrain analysis. The terrain viewshed refers to the range that can be seen at the current position, which varies with the nature of the observer. When the observer is a wireless signal tower, it is the communication viewshed, which refers to the area consisted of grid cells where the receiving antennas can receive the signals from a transmitting antenna set up on a grid cell of terrain. The core of base station location problem includes two aspects: combinatorial optimization and the calculation of the coverage rate of signal. The calculation of communication viewshed is an important research content for determining signal coverage range. In this article, we propose an accurate communication viewshed computation algorithm for wireless signal (CVCWS) using the projection curve of 3D Fresnel zone analysis based on DEM. The CVCWS method can calculate the signal reception quality at different locations more precisely. Besides, a signal attenuation model is proposed to compute the theoretical attenuation value according to the signal receiving quality index. The proposed algorithm is compared with the existing DEM‐based communication viewshed algorithms, and the theoretical attenuation values are compared with the measured values. The experimental results show that the theoretical values gained by the CVCWS algorithm are close to the measured values, indicating high accuracy of the CVCWS algorithm. The proposed method can provide theoretical support for communication tower location planning and other related applications.

Iodine density of lymphoma, metastatic SCCA, and normal cervical lymph nodes: Based on DLSCT

Objective To compare iodine density (ID) and contrast-enhanced attenuation value (CEAV) from dual-layer spectral computed tomography (DLSCT) scans of lymphomatous, metastatic squamous cell carcinoma (SCCA), and normal cervical lymph nodes. Methods Data including ID and CEAV were retrospectively collected from patients who underwent DLSCT of the neck between January 2020 and August 2023. Results from each group (lymphomatous, metastatic SCCA, and normal) were compared and analyzed using one-way ANOVA and receiver operating characteristic curve. Results 129 cervical lymph nodes were collected from patients who met the inclusion criteria (50, 41, and 38 nodes from the lymphomatous, metastatic SCCA, and normal group, respectively). The mean ID of lymphomatous, metastatic SCCA, and normal nodes was 1.01±0.27, 1.36±0.28, and 1.45±0.29 mg/mL, respectively. Comparing lymphomatous nodes with metastatic SCCA nodes, the lymphomatous nodes had significantly lower values of ID (p&lt;0.002) and CEAV (p&lt;0.001). Similarly, when comparing lymphomatous nodes with normal nodes, the lymphomatous nodes had significantly lower values of ID (p&lt;0.001) and CEAV (p&lt;0.001). The optimal ID cut-off value for distinguishing between lymphomatous and metastatic SCCA nodes was 1.175 mg/ml (specificity of 84.2%, sensitivity 77.8%, AUC 0.788, P = 0.003). The optimal CEAV cut-off value was 77.5 HU (specificity 88.9%, sensitivity 78.9%, AUC 0.851, P&lt;0.001). Conclusions The ID and CEAV measurements from DLSCT were significantly different between lymphomatous, metastatic SCCA, and normal lymph nodes. These findings indicate that DLSCT can be used to distinguish between these conditions in the diagnosis of cervical lymph nodes.

Determining risk factors for vascular and bleeding complications after TAVR using CT angiography

Abstract Funding Acknowledgements None. Introduction The use of pre-procedural computed tomography angiography (CTA) of the iliofemoral sector in the planning of transaortic valve replacement (TAVR) has demonstrated a reduction in the risk of vascular complications in patients undergoing TAVR. In this study, we aimed to characterise the clinical and radiological factors associated with bleeding and vascular complications after TAVR. Methods Patients undergoing transfemoral TAVR in a tertiary centre between 2017 and 2019 were included in this analysis. All patients underwent iliofemoral CTA before the procedure and classical CTA-derived data as well as iliofemoral calcium volume were collected. Clinical data and outcomes regarding bleeding events, as well as vascular complications according to Valve Academic Research Consortium 2 (VARC-2) criteria, were also collected. 207 patients were included in this analysis, of whom 53% were women. The median age was 82 years (IQR 76-86) and the median STS mortality risk score was 3.9% (IQR 2.59-5.99). In this population, vascular complications according to the VARC-2 criteria occurred in 33% of patients (19% with major complications). Patients with lower body mass index (BMI) were more likely to suffer vascular complications. Vascular access with fluoroscopy was associated with a higher prevalence of complications compared to ultrasound-guided vascular access (62% vs. 38%, p=0.037). When considering radiological criteria, smaller minimum luminal diameter and area of the common femoral and external iliac arteries were associated with a greater risk of vascular complications, as were increased sheath to external iliac artery ratios and luminal attenuation values (p&amp;lt;0.05 for all). Bleeding complications occurred in 20 patients, with a greater prevalence of bleeding events in female patients (77% vs. 23%, p=0.001). Patients with a lower BMI, a history of obstructive pulmonary disease or coronary artery disease, aortic insufficiency and fluoroscopic valvular access were more likely to have bleeding complications. Regarding radiological criteria, decreased maximal luminal diameter of the common femoral artery and smaller minimal luminal diameters and areas of the external iliac artery were associated with bleeding complications. Increased sheath-to-femoral artery ratios and luminal attenuation values were associated with an increased risk of vascular complications (p&amp;lt;0.05 for all). Conclusion Our study underscores the importance of pre-procedural CTA in TAVR planning and identifies separate risk factors for vascular and bleeding complications.

Evaluation of image quality on low contrast media with deep learning image reconstruction algorithm in prospective ECG-triggering coronary CT angiography.

To assess the impact of low-dose contrast media (CM) injection protocol with deep learning image reconstruction (DLIR) algorithm on image quality in coronary CT angiography (CCTA). In this prospective study, patients underwent CCTA were prospectively and randomly assigned to three groups with different contrast volume protocols (at 320mgI/mL concentration and constant flow rate of 5ml/s). After pairing basic information, 210 patients were enrolled in this study: Group A, 0.7mL/kg (n = 70); Group B, 0.6mL/kg (n = 70); Group C, 0.5mL/kg (n = 70). All patients were examined via a prospective ECG-triggered scan protocol within one heartbeat. A high level DLIR (DLIR-H) algorithm was used for image reconstruction with a thickness and interval of 0.625mm. The CT values of ascending aorta (AA), descending aorta (DA), three main coronary arteries, pulmonary artery (PA), and superior vena cava (SVC) were measured and analyzed for objective assessment. Two radiologists assessed the image quality and diagnostic confidence using a 5-point Likert scale. The CM doses were 46.81 ± 6.41mL, 41.96 ± 7.51mL and 34.65 ± 5.38mL for Group A, B and C, respectively. The objective assessments on AA, DA and the three main coronary arteries and the overall subjective scoring showed no significant difference among the three groups (all p > 0.05). The subjective assessment proved that excellent CCTA images can be obtained from the three different contrast media protocols. There were no significant differences in intracoronary attenuation values between the higher HR subgroup and the lower HR subgroup among three groups. CCTA reconstructed with DLIR could be realized with adequate enhancement in coronary arteries, excellent image quality and diagnostic confidence at low contrast dose of a 0.5mL/kg. The use of lower tube voltages may further reduce the contrast dose requirement.

Carotid artery calcium score: Definition, classification, application, and limits.

In the current paper, the "carotid artery calcium score" method is presented with the target to offer a metric method to quantify the amount of calcification in the carotid artery. The Volume of Interest (VOI) should be extracted and those voxels, with a Hounsfield Unit (HU) value ≥130, should be considered. The total weight value is determined by calculating the sum of the HU attenuation values of all voxels with values ≥130 HU. This value should be multiplied by the conversion factor ("or voxel size") and divided by a weighting factor, the attenuation threshold to consider a voxel as calcified (and therefore 130 HU): this equation determines the Carotid Artery Calcium Score (CACS). In order to provide the demonstration of the potential feasibility of the model, the CACS was calculated in 131 subjects (94 males; mean age 72.7years) for 235 carotid arteries (in 27 subjects, unilateral plaque was present) considered. The CACS value ranged from 0.67 to 11716. A statistically significant correlation was found (rho value = 0.663, p value = .0001) between the CACS in the right and left carotid plaques. Moreover, a statistically significant correlation between the age and the total CACS was present (rho value = 0.244, p value = .005), whereas no statistically significant difference was found in the distribution of CACS by gender (p = .148). The CACS was also tested at baseline and after contrast and no statistically significant difference was found. In conclusion, this method is of easy application, and it weights at the same time the volume and the degree of calcification in a unique parameter. This method needs to be tested to verify its potential utility, similar to the coronary artery calcium score, for the risk stratification of the occurrence of cerebrovascular events of the anterior circulation. Further studies using this new diagnostic tool to determine the prognostic value of carotid calcium quantification are needed.