Abstract:Seismic arrival time data from broadband arrays deployed along the Longmenshan fault zone were used to invert three-dimensional fine structure models of VP,VS,and VP/VS at depths less than 24km and earthquake relocation in the Longmenshan fault zone using the consistency-constrained double-difference tomography method.The results are as follows:(1)The Longmen Shan fault zone exhibits a high-velocity zone between the Beichuan-Yingxiu fault and the Maoxian-Wenchuan fault zone.Within the depth range of 0-8km,this high-velocity zone is confined beneath the Longmen Shan fault zone.Between depths of 8-20 km,the high-velocity zone merges with the high-velocity zone associated with the Maoxian-Wenchuan ductile shear zone.At depths ranging from 20-24km,the high-velocity zone becomes concentrated in the central segment of the Longmen Shan fault zone.The Western Sichuan foreland extensional deformation belt on the southeastern side of the Anxian-Guanxian fault maintains consistently low velocities.(2)Earth-quakes within the Longmenshan fault zone are predominantly concentrated at depths ranging from 4 to 16km beneath the Beichuan-Yingxiu fault zone.Seismic activity shows a significant correlation with transitional zones,which signifies shifts between high and low seismic wave velocities as well as regions characterized by elevated velocity ratios.The dip angles of the seismic distribution and velocity anomalies vary across the southern,central,and northern segments of the Longmenshan fault zone.In the northern segment of the Longmenshan fault zone,both high-velocity bodies and earthquakes are concentrated within a depth range of 0-15km,with an almost vertical dip orientation.(3)The combined analysis of tomographic velocity structures and fracture characteristics in the reflection profiles reveals a Y-shaped hidden fault within the seismogenic zone of the Lushan earthquake.The seismogenic area of the Lushan earthquake is overlain by an aseismic zone layer measuring 10-15km thick.

Abstract:Objective:In order to explore the quantitative indicators based on CT voxel,analyze the risk factors related to the severity of chronic obstructive pulmonary disease(COPD),and establish an individualized nomogram model for predicting severe COPD.Methods:From May 2020 to September 2021,a total of 118 eligible COPD patients were enrolled in the Affiliated Hospital of Yan'an University after dual gas phase scanning and pulmonary function tests.According to the severity classification of COPD(GOLD)(group),the patients were divided into mild COPD group(GOLDI,II):66 cases;Severe COPD group(GOLD III,IV):52 cases.The quantitative and clinical indexes of dual-gas phase registration CT between mild and severe COPD groups were compared.SPSS and R software were used for statistical analysis,and a nomogram model was established to analyze the independent risk factors of severe COPD.Results:The percentage of functional small-airway disease area(fSAD%)and that of emphysema area(Emph%)in the severe COPD group were higher than those in the mild COPD group.With the increase of COPD severity,the pulmonary function indexes FVC,FEV1%pred,and FEV1/FVC%decreased.The smoking index,fSAD%,and Emph%of the severe COPD group were higher than those of the mild COPD group.Through analysis,it was found that the smoking index and CT quantitative indicators(fSAD%,Empire%,and Normal%)are independent risk factors for severe COPD.Furthermore,a risk model for predicting severe COPD was established.CT quantitative indicators have a relatively greater impact on the weight of patient mortality risk than smoking index.The column chart prediction model was internally validated through a calibration chart,which showed that the model calibration curve was close to the standard curve.Conclusion:Quantitative indicators based on CT voxels can predict the severity of COPD.The established column chart model for predicting COPD severity through CT quantitative indicators and smoking index has good diagnostic efficacy.

Abstract:An intra-crustal MW8.8 strong earthquake occurred off the eastern coast of Kamchatka,triggering a tsunami and attracting global attention.Some researchers have analyzed the mechanical mechanism of this strong earthquake from the stress field.We utilizes our previous results via seismic tomography to analyze the relationship between the velocity structure and this strong earthquake according to the seismic wave velocity,and compares it with the 2011 Japan earthquake to discuss the triggering effect of deep fluids on the MW 8.8 earthquake.

Abstract:Objective:To investigate the effect of different tube projection angles in scout imaging using automatic tube-current modulation(ATCM)and spectral-shaping technology on radiation dose and image quality in head CT examinations.Methods:Head-neck phantoms are used for helical scans with ATCM.Combinations of tube projection angle include anteroposterior(AP),posteroanterior(PA),lateral(LAT),AP+LAT,and PA+LAT.The helical scan tube voltages are 120kV,80/140kV,Sn150kV,70/Sn150kV,80/Sn150kV,90/Sn150kV,and 100/Sn150kV.Each scan method is repeated thrice.The volume CT dose index(CTDIvol)and dose-length product(DLP)are recorded,and the lens organ dose is measured using a thermoluminescent dosimeter.At the central orbital plane,regions of interest(ROIs)are delineated,with the centers of the left and right eyeballs as well as the brainstem designated as signal regions,and air as the background region.The contrast-to-noise ratio(CNR)is calculated based on the mean CT values and standard deviations of the ROIs.Based on the ocular and brainstem CNRs as well as the lens organ dose,the figures-of-merit(FOMs)for the eyes and brainstem are calculated.A generalized estimation equation is established for the FOM of different scout-image combinations,and the model is constructed using an equicorrelation structure matrix.Results:CTDIvol and lens organ dose:Both single-and dual-tube conventional and spectral filtration groups yield the highest values for PA positioning and the lowest values for lateral positioning.CNRs of eye and brainstem:For 120kV,Sn150kV,and dual-tube spectral filtration groups,the highest CNR is observed in PA positioning,whereas the lowest in lateral positioning.For 80/140kV,the highest CNR is observed in(PA+lateral)positioning,and the lowest in lateral positioning.The projection angles of different scout-image tubes significantly affect the FOM.At 120kV,the highest FOM is indicated by(PA+lateral)positioning,whereas at Sn150kV,the highest is indicated by PA positioning.For dual-tube conventional and spectral filtration groups,the lateral positioning indicates the highest FOM.Conclusion:The selection of scout images affects the effectiveness of ATCM under spectral shaping.Under Sn150kV,the use of PA scout images is recommended,whereas the use of LAT scout images is recommended for dual-source spectral shaping.

Abstract:Epithelial-myoepithelial carcinoma(EMC)is a rare low-grade malignant salivary gland-type tumor.It mostly occurs in the parotid gland,followed by the submandibular gland and minor salivary glands.However,primary EMC of the lung is extremely rare,and has been reported in mostly case reports of national and international origin.Currently,there is no report of pulmonary EMC with recurrent primary breast cancer.To improve the awareness of this disease,we here report one such case of a patient admitted to our hospital.

Abstract:Fine-scale intracrustal interface structures record regional tectonic deformation and evolutionary history and constitute critical constraints for seismic hazard assessment and mineral resource exploration.In recent years,teleseismic body-wave imaging has advanced substantially,transcending their limitations in mantle and bulk crust studies to reveal,with unprecedented precision,multiscale crustal interfaces from sedimentary layers to the Moho.Here,we review the latest research progress in teleseismic body-wave imaging of crustal interfaces from two perspectives,teleseismic converted-and reflected-wave imaging,focusing on receiver function and teleseismic virtual-source reflection techniques.For receiver functions,we emphasize methodological advances and applications in imaging shallow crustal structures while examining current trends such as dense array deployments,migration imaging,and multi-method joint inversions.We discuss the fundamental principles and field applications of teleseismic virtual source reflection imaging using four key techniques:deconvolution,autocorrelation,cross-correlation,and reverse-time migration.Finally,we summarize the current research status and emerging trends in the teleseismic imaging of intracrustal interfaces and discuss future directions.

Abstract:The Qilian Orogenic Belt,located at the northeastern margin of the Tibetan Plateau with the Central Qilian Block at its core,plays a significant role in regional tectonic evolution.To reveal the crustal velocity structure of the Qilian Orogenic Belt and investigate the relationship between velocity structure and seismic activity,this study utilized P-wave and S-wave arrival time data recorded by seismic networks in Gansu,Qinghai,and other regions under the China Earthquake Networks Center.A double-difference tomography method was applied to relocate 6,617 seismic events in the study area,and 3D P-wave/S-wave velocity structures as well as velocity ratio distributions were obtained.The double-difference tomography produced several interesting results:(1)The Central-Northern Qilian Fault Zone exhibits distinct segmentation in activity along its eastern and western sectors.The eastern segment is dominated by shallow-seated faulting(0-10km),whereas the western segment features deeper-seated tectonic activity(15-25km).This indicates more pronounced upper crustal thickening in the western sector of the Qilian orogenic belt.Large earthquakes are concentrated in high-velocity anomaly regions of the upper-middle crust,suggesting that brittle crust is more prone to fault rupture.(2)Both velocity structures and velocity ratio distributions show a vertical transition from high to low values,indicating that the upper-middle crust of the Qilian Orogenic Belt is more rigid,whereas the middle-lower crust may include dehydration reactions of hydrous minerals.(3)There is a significant interface separation between the Central Qilian Block and the North Qilian Orogenic Belt in the upper-middle crust,which corresponds well with the south-deep and north-shallow distribution characteristics of sedimentary rock layer thickness in the Qilian Orogenic Belt.

Abstract:The Feldkamp-Davis-Kress(FDK)algorithm has the advantages of a simple structure,fast calculation speed,and high reconstruction quality,and it remains the mainstream algorithm for cone-beam computed tomography(CBCT)analytical reconstruction.However,if the cone angle for the reconstructed point is too large,the reconstruction exhibits artifacts characterized by an axial density drop.Numerous methods for suppressing this artifact have been proposed,including projection weighting,cone-beam rebinning,and introducing compensation terms.The compensation method has high computational efficiency and achieves good artifact suppression when the cone angle is over ten degrees.However,for cases with larger cone angles,the effectiveness of this algorithm is diminished.Thus,further optimization of the reconstruction algorithms and scanning geometry is required to accommodate industrial and clinical demands.Based on the two compensation terms for FDK reconstruction,this study extends cone-beam CT geometrically to the case of dual source in the z-direction distribution,further suppressing cone-beam artifacts by reducing the average cone angle of the reconstructed points.A cone-angle weighting method is proposed for dual-source reconstruction,to fuse the reconstructed results of the two sources and obtain the final reconstructed image.Simulation results show that the proposed algorithm can improve the quality of the reconstructed image more effectively than single-source case.

Abstract:Radiation dose reduction in computed tomography(CT)can be achieved by decreasing the number of projections.However,reconstructing CT images via filtered back projection algorithm from sparse-view projections often contains severe streak artifacts,affecting clinical diagnosis.To address this issue,this paper proposes TransitNet,an iterative unrolling deep neural network that combines model-driven data consistency,a physical a prior constraint,with deep learning's feature extraction capabilities.TransitNet employs a novel iterative architecture,implementing flexible physical constraints through learnable data consistency operations,utilizing Transformer's self-attention mechanism to model long-range dependencies in image features,and introducing linear attention mechanisms to reduce self-attention's computational complexity from quadratic to linear.Extensive experiments demonstrate that this method exhibits significant advantages in both reconstruction quality and computational efficiency,effectively suppressing streak artifacts while preserving structures and details of images.

Abstract:At the microscale,the different minerals,pores,and microcracks in granite create heterogeneity,thereby impacting the formation and progression of microfractures.This study examined the generation and development of thermal cracks in a Westerly granite sample,using high-resolution,in-situ heating synchrotron CT observations from room temperature up to 395℃.The discrete element method was subsequently employed to create models based on the CT images,including different minerals and pre-existing pores and cracks,to simulate the development of thermal cracks.The CT images revealed small pores within and between the granite mineral grains,as well as numerous cracks between them.Newly formed thermal cracks were detected at approximately 100℃ with larger cracks appearing at temperatures>200℃,eventually resulting in a network of cracks.Numerical simulations using the discrete element method demonstrated that thermal cracks primarily develop at the interfaces between the different minerals.The temperature and distribution of simulated cracking correlate well with the CT observations.A comparison with model simulations without pre-existing pores showed that these pores resulted in lower thermal stress within the mineral grains and a lower initial temperature at which thermal cracks formed.This indicates that granite containing pre-existing pores/cracks would be damaged at temperatures of 200℃ or lower.These findings enhance our understanding of the development of thermal damage in different granites and offer insights for predicting thermal damage in rocks.

Abstract:Objective:This study aimed to explore the clinical use of the chest computed tomography(CT)subtraction technique for evaluating the degree of chest mass enhancement.Methods:Patients with suspected chest masses who underwent contrast-enhanced chest CT were retrospectively enrolled.Contrast-enhanced CT used was performed using lung subtraction.Subtraction images were reconstructed,and color fusion images of the iodine distribution in the chest masses in the arterial and venous phases were obtained after subtraction.The net enhancement value(∆Hu)was measured and calculated,∆Hu=after-before enhancement value.The enhancement degree were divided into mild(∆Hu<20HU),moderate(∆Hu 20-40HU),and significant(∆Hu>40 HU).The CT subtraction iodine maps were visually evaluated.The net perfusion value(∆Husub)of CT lung subtraction iodine maps in arterial phase and venous phase was measured.McNemar and kappa tests were used to evaluate the difference and consistency of∆Hu and∆Husub degrees,respectively.The paired t test was used to compare the differences between∆Hu and∆Husub.Results:This study included 34 patients(37 lesions).Data measured by the three observers were in good agreement.The∆Hu and∆Husub degrees had no significant difference,but had good consistency.No significant differences were observed between ∆Hu and ∆Husub in the arterial and venous phases.Conclusion:Lung subtraction CT imaging can simplify the steps of image reading and report writing by reducing the measurement and calculation time for lung lesions without increasing scanning time,which contributes to improving the efficiency of diagnosis.

Abstract:Objective:We evaluated the feasibility,safety,and impact of the use of fused computed tomography-digital subtraction angiography(CT-DSA)-guided imaging in catheter ablation(CA)combined with left atrial appendage occlusion(LAAO)on left heart function.Methods This single-center retrospective study was conducted from July 1,2023,to December 30,2023,at the First Affiliated Hospital of Guangzhou University of Chinese Medicine.This study included patients who received combined CA and LAAO(combined group)or CA alone(CA-only group).The primary outcome was perioperative complications within 7 days of surgery,and the secondary outcomes included the results of the 6-month follow-up and the echocardiographic evaluation of left heart function.Results The procedures were successfully completed for the combined(n=40)and CA-only(n=55)groups,with no significant differences in perioperative complications.The atrial fibrillation-free rates were similar between the combined and CA-only groups at the 6-month follow-up,(70%vs.74.5%).The left atrial anteroposterior diameter(LAAD)was significantly lower at 6 months(preoperative:(46.32±5.14)mm vs.6 months:(42.13±5.94)mm),and left ventricular ejection fraction(LVEF)increased but was not statistically significant in the combined group than prior to surgery,while the LVEF significantly increased in the CA-only group.The increase in LVEF was statistically significant in the CA-only group 6 months after surgery compared with LVEF prior to surgery.The left ventricular filling pressure(E/E´)significantly increased in the combined group post-surgery compared to the pressure before surgery.Conclusions CA combined with LAAO guided by fused CT-DSA imaging is a safe and feasible treatment option for selected patients with atrial fibrillation.Furthermore,the combined procedure has no significant impact on left ventricular systolic function.

Abstract:Objective:To explore the application value of dual-energy CT virtual non-contrast(VNC)instead of true non-contrast(TNC)in reducing the radiation dose of small intestine radiography in Crohn's disease.Methods:Dual-energy enterography images of 53 patients with Crohn's disease in the First Affiliated Hospital of Nanjing Medical University from June 2024 to December 2024 were obtained.Virtual non-contrast images of the arterial phase and venous phase were reconstructed using dual-energy analysis software.One-way analysis of variance was used to evaluate the CT values,signal-to-noise ratio(SNR),and contrast-to-noise ratio(CNR)of conventional plain scan and virtual plain scan images in the arterial and venous phases.The image quality was subjectively evaluated by the 5-point method and analyzed by the rank sum test.The subjective image quality scores of TNC,VNCa and VNCv were 4(4,5),4(4,5)and 4(4,5)respectively,and the difference was not statistically significant.There was no statistically significant difference in the CT values of the diseased intestinal wall,normal intestinal wall,inferior vena cava,erector spinae muscle and liver among TNC,VNCa and VNCv.The SNR values of the diseased intestinal wall,normal intestinal wall,abdominal aorta,inferior vena cava and liver were statistically significant,and the SNR values of VNCa and VNCv were both higher than those of TNC.There was no statistically significant difference in the CNR values among the diseased intestinal wall,normal intestinal wall,inferior vena cava and liver.The radiation dose of VNCv scan is approximately 30%lower than that of TNC CTE scan.Conclusion:The virtual non-contrast of dual-energy CT instead of the true non-contrast can reduce the radiation dose of enterography in Crohn's disease while ensuring image quality,and can be promoted in clinical applications.

Abstract:Objective:To investigate the value of computed tomography-based extracellular volume fraction(ECV)for preoperative evaluation of WHO/ISUP pathologic grading of clear cell renal cell carcinoma(ccRCC).Methods:Seventy-two patients with ccRCC who underwent postoperative histological confirmation were retrospectively enrolled.All patients underwent preoperative CT scanning of the abdomen and three-phase enhancement scanning according to the WHO/ISUP grading.Grades I and II were categorized as the low-grade group(48 patients)and grades III and IV were categorized as the high-grade group(19 patients).General clinical data of the two groups were collected,and quantitative parameters,including delayed aortic net value added(∆HUAorta),delayed tumor net value added(∆HUtumor)and ECV,were measured and compared,and the diagnostic efficacy of ECV in the pathological grading of ccRCC was evaluated by plotting the receiver operating characteristic curve(ROC).Results:The∆HUtumor and ECV of ccRCC in low-grade group were significantly higher than those in high-grade group.The ROC curves demonstrated that the efficiency of ECV in evaluating WHO/ISUP low-grade ccRCC(AUC:0.834)was higher than that of∆HUtumor(AUC:0.725).Conclusion:CT-based ECV is valuable for the preoperative evaluation of ccRCC pathological grade.

Abstract:Objective:We aimed to develop a predictive model for lung adenocarcinoma with ground glass nodules(GGNs)based on artificial intelligence(AI)and computed tomography(CT)features,and to evaluate the model's predictive value.Methods:A total of 261 GGNs from 225 patients diagnosed after surgery at our hospital were retrospectively collected and randomly divided into a training set and a validation set in an 8∶2 ratio.The GGNs were classified into preneoplastic lesions and adenocarcinoma groups based on pathological results.AI-derived quantitative parameters and CT signs from the training set were compared between the two groups,and independent risk factors were identified using multivariate logistic regression.A predictive model and nomogram were developed,and model performance was assessed through the area under the receiver operating characteristic curve(ROC)curve area under the curve(AUC),calibration curve,and clinical decision curve analysis(DCA).The model was subsequently validated using the validation set.Results:Kappa test indicated good agreement between the two attending physicians in their assessment of CT signs.Baseline analysis revealed no statistical differences between variables in both training and validation sets.In the training set,lobulation sign(OR=3.147,95%CI:1.303-7.601),vacuole sign(OR=2.563,95%CI:1.109-5.922),vascular abnormalities(OR=3.551,95%CI:1.545-8.164),long diameter(OR=1.154,95%CI:1.014-1.312),and mean CT value(OR=1.006,95%CI:1.003-1.009)were identified as independent risk factors for adenocarcinoma in GGN after univariate and multivariate analysis.The predictive model constructed based on this information showed good discrimination ability,with an AUC of 0.901(95%CI:0.859-0.943)in the training set and an AUC of 0.896(95%CI:0.810-0.983)in the validation set,significantly outperforming individual risk factors.The Hosmer-Lemeshow test demonstrated good model fit in both sets and DCA showed its strong clinical applicability.Conclusion:The model based on AI and CT signs demonstrated good predictive performance for GGN lung adenocarcinoma,providing valuable insights for clinical decision-making.

Abstract:Dense-array observation has become a key method for obtaining high-resolution subsurface structures.However,the spatiotemporal heterogeneity of the noise source distribution significantly reduces the signal-to-noise ratio(SNR)of noise correlation functions(NCF),thereby affecting the extraction of dispersion curves.This study analyzed the noise level characteristics in low-frequency(0.1-1Hz)and high-frequency(1-10Hz)bands across dense arrays in typical tectonic regions of eastern and western China,including the Ganyanchi pull-apart basin in Ningxia on the northeastern Tibetan Plateau,the Sanshui Basin in Guangdong,and the Beiliu seismic source area in Guangxi.The Sanshui Basin and Beiliu seismic source area are located on the northern continental margin of the South China Sea and exhibit relatively uniform noise levels in the low-frequency band.High-SNR Rayleigh wave signals were successfully extracted in the 0.1-1Hz range,enabling effective derivation of dispersion curves using the Frequency-Bessel transform method.Conversely,the Ganyanchi pull-apart basin in the northeastern Tibetan Plateau shows low noise intensity in the low-frequency band,where the basin-mountain coupled topography induces precursor wave interference with near-zero time delays in the NCF waveforms.At high frequencies,localized nonstationary noise wavefields result in low-SNR Rayleigh wave signals within a 4 km range,accompanied by chaotic,non-convergent signals that hinder dispersion curve extraction.Thus,prior to ambient noise data acquisition,the distribution characteristics of ambient noise sources and regional tectonic features must be analyzed to determine the observation scheme.

Abstract:Objective:We explored the application value of multi-slice spiral computed tomography(MSCT)in preoperative prediction of the degree of pathological differentiation of peripheral lung squamous cell carcinoma(PLSCC).Methods:A total of 76 lesions from 75 patients with PLSCC confirmed by pathology in our hospital from January 2020 to November 2023 were selected and divided into a well-to-moderately differentiated group(n=55)and a poorly differentiated group(n=21)according to their pathological differentiation grades.The MSCT features of the two groups were compared and analyzed,including tumor size,shape,location,cavity,calcification,and signs of lobulation,air bronchogram,spiculation,vacuole,vascular convergence,pleural indentation,bronchial crawling,and bronchial truncation.Results:Compared with the poorly differentiated PLSCC group,the well-to-moderately differentiated PLSCC group had larger lesions,more signs of air bronchogram,and fewer signs of lobulation.These differences between groups were statistically significant.Conclusions:Some MSCT detected PLSCC features correlate with its degree of pathological differentiation and can be used to predict the pathological differentiation degree of PLSCC preoperatively.

Abstract:The Namche Barwa massif is located in the core area of the eastern Himalayan syntaxis.This area is located at the junction of the Eurasian plate,Indian plate and Myanmar block.It is the key part of the southeastward lateral strike-slip extrusion and 90° deflection of the plate boundary on the Tibetan Plateau.It is also the region with the strongest tectonic stress and the fastest uplift rate and denudation.It is of great significance to study the velocity structure of this area to understand the mechanism of earthquake preparation.On the basis of the dense array data of 374 short-period nodal seismometers deployed in the Namche Barwa area between June 14 and July 24,2020,in combination with the data of the regional seismic network from 2009 to 2024,the double-difference tomography method was used in this study to obtain the velocity structure characteristics and precise relocation of earthquake results of Namche Barwa and its vicinity.The results show the north and east sides of the Namche Barwa peak are located in the high-velocity anomaly area,whereas the southwest side is located in the low-velocity anomaly area.At a depth of 10km with high resolution,the P-wave velocity structure in the middle section of the Jiali fault changed from high-velocity anomaly to low-velocity anomaly.The trend of P-wave and S-wave high-velocity and low-velocity anomaly areas is consistent with the trend of the main active fault zones.From a depth of 5km,the wave velocity ratio of the Namche Barwa massif and its vicinity is low,and the phenomenon is more significant with the increase in depth.

Abstract:The conventional view suggests that the subduction of the South China Sea plate beneath Luzon occurred due to the oceanic lithosphere's high density,facilitating subduction initiation.However,before the South China Sea opened,a continental margin likely existed,meaning that Luzon was directly adjacent to the continental margin rather than the oceanic basin.This would make subduction initiation more challenging.Here,we propose a new model suggesting that during the formation of the South China Sea,extensive mafic magmatic underplating occurred along its continental margin.The high-density magmatic additions may have increased the overall density of the continental margin,potentially exceeding that of Luzon,thereby enabling subduction to proceed.