CT理论与应用研究

Method on 3D Tomography of S-wave Velocity Azimuthal Anisotropy by Using Surface-wave Dispersion Curves

FENG Mei, AN Meijian

2020, 29(4): 381-397. doi: 10.15953/j.1004-4140.2020.29.04.01

Abstract(543) PDF(19)

Abstract:
Seismic anisotropy is one of the important indicators reflecting internal medium character of the Earth.The commonly used shear wave splitting method and two-dimensional(2D) tomography of surface-wave azimuthal anisotropy are difficult to accurately reflect the change in anisotropy with depth.Converting the period-dependent regionalized surface-wave azimuthal anisotropy into depth-dependent one-dimensional(1D) S-wave velocity azimuthal anisotropy is one way to make up for the lack of depth information.The existing researches on three-dimensional(3D) S-wave velocity anisotropy are normally implemented by a two-step method including period-by-period 2D tomography of surface-wave azimuthal anisotropy and grid-by-grid 1D inversions for S-wave velocity anisotropy.This stepwise method is neither conducive to the use of 3D a priori constraints,nor conducive to the direct evaluation of the inverted 3D model by checking misfit of original observational data.Therefore,we developed a method on 3D tomography of S-wave velocity azimuthal anisotropy by using surface-wave dispersion curves and implemented the relative forward and inversion programs.In order to check the effectiveness of the methods and procedures,we conducted synthetic tests for regularly distributed checkerboard models.Test results show that:this method can well recover 3D structural information such as isotropic velocity anomalies,relative anisotropic intensity,and fast wave direction;the inverted model significantly improves the fit and reduces the misfit to the observation data compared to the reference model.However,given an isotropic synthetic model,the 3D anisotropic inversion can result in<0.5%of false anisotropy in homogenous areas,and the false anisotropy increases for strongly heterogeneous areas,reaches up to 3.5%at shallow depths.So,in practical studies,interpretation on anisotropy in strongly heterogenous area(especially at shallow depths) must be cautiously treated.

HRCT Ground-Glass Opacity Characteristics, Anatomy and Pathological Basis of COVID-19

CHE Qinglin, GAO Yanjun, JI Xiaoxiao, JIA Rongrong, ZHANG Lang, BAI Weixian, LV Hairong

2020, 29(4): 399-406. doi: 10.15953/j.1004-4140.2020.29.04.02

Abstract(400) PDF(7)

Abstract:
Objective:To summarize the characteristics of COVID-19 ground glass opacity(GGO) on HRCT, and to explore its anatomical and pathological basis.Methods:The HRCT imagings of 87 cases with COVID-19 were analyzed retrospectively and the characteristics of GGO were summed up. Results:A total of 255 GGO lesions were found, and their distribution characteristics were as follows:4 in the central region(1.57%), 120 in the peripheral region(47.06%), and 131 in the subpleural region(51.37%). The structural features of the lesions:48 lesions with paving stone signs(18.82%), and 191 lesions with small thickened blood vessels.The marginal features:96 lesions with arcuate indentations(37.65%) and 75 lesions with pleural traction signs(29.41%). Conclusion:The peripheral distribution of GGO is the typical HRCT manifestation of COVID-19, and paving stone sign, arcuate indentation sign and pleural traction sign are the manifestations of the lesion organization and fibrosis.

The Initial Study of Clinical and CT Diagnostic Characteristics about Corona Virus Disease 2019: Case Review in Dongguan

WANG Gang, XIE Haofeng, ZHENG Xiaolin, FANG Xuewen, YU Fenfen, YUAN Huanchu, DU Heqin, ZOU Yujian

2020, 29(4): 407-415. doi: 10.15953/j.1004-4140.2020.29.04.03

Abstract(348) PDF(7)

Abstract:
Objective:The clinical and chest CT features of COVID-19 cases were analyzed retrospectively. To know more deeply about the disease and promote the diagnosis and treatment of the disease. Method:70 cases of COVID-19 in Dongguan were included. Of all cases, the routine blood test and C-reactive protein test were performed. 69 cases underwent chest CT examinations. The thickness and interval of CT examination were 1.25 mm. CT images were evaluated by the following indications:location and number, distribution, shape, density, internal characteristics, margin, halo sign of intra-pulmonary lesion and extra pulmonary signs. Results:There were 37 males and 33 females with an average age of(41.29 ±17.86) years. 45 cases(64.29%) had fever in the first visit, leukocyte count was normal or decreased in 67 cases(95.71%), lymphocyte count was decreased in 52 cases(74.29%), C-reactive protein value was increased in 43 cases(61.43%). Chest CT image findings:55 cases showed pneumonic imaging signs of all 69 patients underwent CT examinations, including 21 unilateral lung lesions and 34 bilatera multiple lesions. 42 cases were mainly distributed under the peripheral pleura, and the shape of the lesions showed various findings, including flaky or patchy exudation, nodular and stripe shaped lesions. The density of the lesions was nonuniform. 44 cases had indistinct edge and 35 cases had halo sign. In all 55 cases, ground-glass opacity lesions were showed. Reticular lesions were showed in 37 cases. There were 52 cases of abnormal bronchovascular bundles findings and 38 cases of abnormal pleural findings. Conclusion:The clinical and CT manifestations of COVID-19 have certain characteristics. It is not difficult to diagnose COVID-19 with the epidemiological history and CT feature. But the special manifestations and differential diagnosis of the disease should be given attention.

The First Clinical and CT Value Analysis of COVID-19

ZENG Ni, HE Jianhua, ZENG Jian, DUAN Xuqiong, XU Xiaomei, QIAO Jie

2020, 29(4): 416-423. doi: 10.15953/j.1004-4140.2020.29.04.04

Abstract(295) PDF(7)

Abstract:
Objective:To analyze the value in the first clinical and chest CT features of Corona Virus Disease 2019(COVID-19). Methods:The first clinical symptoms、general inflammatory indicators and chest CT features of 90 patients with clinically diagnosed COVID-19 were retrospectively analyzed, which included 13 cases of severe/critical type and 77 cases of light/ordinary type. The results were analyzed and compared by two experienced radiologists. Results:Compared with the light/ordinary COVID-19 patients, the most important clinical characteristics of the severe/critical type were older age, general inflammatory indicators increased, and chest CT showed higher pulmonary inflammatory index(PII). The receiver operating characteristic curve(ROC) showed that the sensitivity of C-reactive protein(CRP) and PII to distinguish between severe/critical COVID-19 and light/ordinary COVID-19 was respectively 69.2% and 69.2%; The specificity was 83.1% and 87.0%, respectively; The Area Under Curve(AUC) were 0.775[95% CI(0.649, 0.901); P=0.002] and 0.770[95% CI(0.621, 0.920); P=0.002], respectively. The AUC of their association was 0.785[95% CI(0.644, 0.927); P=0.001]. Conclusion:Clinical symptoms, inflammatory indicators and chest CT features were significantly different between severe/critical COVID-19 and light/ordinary COVID-19 patients, and it is helpful for early identification of severe/critical COVID-19 and assessment of its prognosis when combined with age, PII and CRP.

Visualization of Pore-Structural Deformation of Dynamic CT Images of a Leitha Limestone

HUANG Wanying, WU Jiangtao, LIU Jie

2020, 29(4): 424-434. doi: 10.15953/j.1004-4140.2020.29.04.05

Abstract(240) PDF(7)

Abstract:
The deforming mechanism of rocks is an important basis for studying the lithosphere deformation and local tectonic activity, while microstructure of rocks is the key to study its deforming mechanism. Microtomography(Micro-CT), which can obtain high-resolution three-dimensional(3D) digital images nondestructively, make it possible to observe the internal structure of rocks. The dynamic CT technique by using HADES device further enables the observation of the deformation process of rocks. In this paper, a set of 3D dynamic CT images of a Leitha limestone experienced triaxial test have been processed to characterize the evolution of pores by using the concept of cluster of percolation theory. The processing and analysis include:image cropping and masking, image segmentation, quantitative analysis and visualization. The visualization of pores has been carried out by presenting:all pores, the largest cluster, small clusters, and fracture-like small clusters. The results show that:(1) the largest percolating pore is continuously reducing while the sample is compressed;(2) new pores or cracks appear in the upper part of the sample in the early steps of the compression;(3) a shear zone emerges in the lower part of the sample after axial strain over 3.5% and it is represented by a large number of small fractures and/or pores in a zone of a dip angle around 45°. This implies that the deformation of the highly porous rock not only exhibits the formation of compaction bands as observed previously, but also shear deformation. The interesting aspect is that the orientations of small fractures distributed along the shear zone do not accompany the orientation of the shear zone, showing there is no predominant direction. This study reveals the concurrency of compaction band and shear zone by the visualization of catalogued clusters. The reason that the orientations of newly created small fractures along the shear zone do not show the same as that of the shear zone may be caused by the complexity of local microstructures of pores. This is worthwhile to be studied further in future.

Low-dose Micro-CT Imaging Method Based on Progressive Network Processing

CAI Ning, WANG Shijie, CHEN Lujie, ZHANG Yikun, CHEN Yang, LUO Shouhua, GU Ning

2020, 29(4): 435-446. doi: 10.15953/j.1004-4140.2020.29.04.06

Abstract(340) PDF(16)

Abstract:
Micro-CT has a wide range of application fields, and has been studied in biomedicine and materials science, and has developed rapidly in recent years. Micro-CT images often suffer from noise due to radiation dose limitations, so it is important to develop an appropriate algorithm to suppress noise in Micro-CT images. The noise level of the Micro-CT image is related to the scanned samples, scanning parameters and other parameters. The noise suppression algorithm should have good performance under different noise levels. In the past, the noise suppression algorithm of Micro-CT images was mainly an iterative reconstruction algorithm, but the iterative reconstruction algorithm was relatively slow. As a popular image processing method in recent years, the deep learning method has better effect and faster processing speed than traditional methods in clinical low-dose CT image processing, and has the potential for further application in low-dose Micro-CT image processing. In addition, generative adversarial networks have better results than convolutional neural networks in maintaining image details. In this paper, ordinary convolutional neural networks and generative adversarial networks are designed to compare their performance differences. Limited to the power of the radioactive source, high-dose Micro-CT images are difficult to acquire. This paper has proposed an innovative scanning method that can effectively obtain low-noise Micro-CT data of mice. Due to high noise of low-dose Micro-CT, combined with the imaging principle of Micro-CT, a progressive low-dose Micro-CT image processing method was proposed, which processed the Micro-CT data before and after analytical reconstruction. Compared with processing only on tomographic images, the progressive method is better for processing high-noise Micro-CT data. From the objective indicators and visual effects, the differences between the progressive method and other deep learning methods or iterative reconstruction algorithms are analyzed and compared. This paper quantitatively analyzes the effect of the processing network on Micro-CT images with different noise levels, and analyzes the advantages and limitations of GAN in progressive Micro-CT image processing. The progressive Micro-CT image processing method generates images with high quality, fast generation speed, high robustness, and high objective index, which can help further advanced applications such as image segmentation and image 3D visualization.

New Exploration of Airport Intelligent Passenger Inspection Channel Based on CT Security Screening Technology

ZHU Taotao, WANG Lijun

2020, 29(4): 447-455. doi: 10.15953/j.1004-4140.2020.29.04.07

Abstract(271) PDF(13)

Abstract:
In order to improve the efficiency of passenger security inspection at domestic airport, reduce the working strength of security personnel, this paper takes the civil aviation passenger hand luggage check security intelligent process as the research direction, presents a new process of intelligent passenger hand luggage security inspection based on CT security inspection technology, and practices the feasibility of the security inspection process at airport. It fills the gap in the research on the application of CT security screening technology for passenger security screening channels at domestic airport. During the trial operation, the intelligent security inspection channel effectively guarantees the travel of civil aviation passengers, no acts of unlawful interference on the flight occurred. Practice shows that the intelligent passenger hand luggage security mode based on CT security equipment proposed in this paper is feasible. This mode has promoted the quality and efficiency of civil aviation security work.

Reliable Study on Computer-aided Evaluation of the Severity of Acute Pulmonary Embolism

HAO Fene, SUN Zhenting, GUO Youmin, ZHAO Lei, LIU Aishi

2020, 29(4): 456-464. doi: 10.15953/j.1004-4140.2020.29.04.08

Abstract(226) PDF(6)

Abstract:
To evaluate the reliability of geometry-based computer-aided detection and quantification for emboli morphology and embolism severity of acute pulmonary embolism. Thirty patients suspected acute PE were analyzed by manual and computer-aided interpretation of vascular obstruction index and computer-aided measurements of emboli quantitative indicators, respectively. The reliabilities of Qanadli and Mastora scores using computer-aided and manual interpretation were analyzed. The time costs of manual and computer-aided interpretation were statistically different(Q:(185.83 ±71.23) s vs.(169.97 ±69.16) s; M:(374.90 ±150.16) s vs.(121.07 ±51.76) s,all P < 0.001). The difference between computer-aided and manual interpretation of Qanadli score was 1.83 ±2.19; 97.5%(39/40) of the measurements were within 95% confidence interval(ICC=0.998). The difference between computer-aided and manual interpretation of Mastora score was 1.46 ±1.62; 97.5%(39/40) of the measurements were within 95% confidence interval(ICC=0.997). The emboli quantitative indicators were moderately correlated with Qanadli and Mastora scores(all P < 0.001). Computer-aided detection and quantification could help to improve the timeliness and reliability of vascular obstruction index, and provide additional and significant quantitative indicators for disease assessment.

Detection Efficiency of Residents Assisted by Artificial Intelligence for Pulmonary Solid Nodules with Different Sizes: A Preliminary Study

SUN Tingting, WANG Qiong, XIE Mei, FAN Hongyu, ZHANG Qing, WU Jianlin

2020, 29(4): 465-472. doi: 10.15953/j.1004-4140.2020.29.04.09

Abstract(283) PDF(4)

Abstract:
Objective:To investigate the clinical application value of artificial intelligence(AI) assisted detection software for improving the detection efficiency of pulmonary solid nodules in inexperienced residents. Methods:A total of 200 CT images of pulmonary solid nodules confirmed by CT were collected. One senior radiologist with more than 8 years' experience read CT images based on the initial diagnosis of another senior radiologist with similar experience and a final decision was subsequently conducted by deputy chief radiologist with more than 15 years' experience to determine the ground truth solid lung nodules. One resident read the images without AI software(method A) and the same resident read CT images with AI software(method B) after two weeks' washout period(method B). The results of methods A and B were compared with the gold standard nodules. The number of true positive nodules and the number of false positive nodules were recorded. The difference between detection sensitivity and false positive rate between the two groups was analyzed by SPSS 20.0. The difference was statistically significant(P < 0.05). Results:Compared with method A, the sensitivity of method B increased significantly, the sensitivity of total solid nodules increased by 65%, and the false positive rate decreased by 25%, the difference was statistically significant(P < 0.05); The sensitivity of the four groups of different sizes(D ≤ 4 mm, 4 mm < D ≤ 6 mm, 6 mm < D ≤ 8 mm, D > 8 mm) for lung solid nodules was improved by AI assisted software, and the increase rate was 78%,38%, 27% and 13.8%, respectively. The area on the FROC curve of method A(AAC) was 0.176, the method B was 0.0852, and the difference was statistically significant(P < 0.05). The average reading time of the two methods A and B was 411.9 seconds and 319.7 seconds respectively. Conclusion:AI assisted software can significantly improve the detection efficiency of inexperienced residents for different sizes of lung solid nodules in CT, especially for the detection of lung solid nodules ≤ 4 mm in diameter.

CT Texture Analysis on the Response Evaluation of Lung Adenocarcinoma Treated by Gifitinib

ZHOU Linli, FENG Feng

2020, 29(4): 473-480. doi: 10.15953/j.1004-4140.2020.29.04.10

Abstract(264) PDF(6)

Abstract:
Objective:To investigate the value of CT texture analysis in the evaluation of response to gefitinib-based treatment in patients with lung adenocarcinoma. Materials and Methods:Twenty-one patients with lung adenocarcinoma who received a treatment of gefitinib were retrospectively analyzed, and were evaluated as partial response(PR) after 3 months treatment based on RECIST 1.1(Response Evaluation Criteria in Solid Tumors, Version 1.1). We obtained and compared the quantitative texture parameters of gray histograms and GLCM on CT scan images before and after 3 months of treatment, respectively. A subgroup analysis of progression-free survival(PFS) of no less than 1 year and less than 1 year, were conducted to compare the changes in texture parameters before and after treatment. Results:Twenty-one patients with lung adenocarcinoma were evaluated as PR after 3 months of treatment with gefitinib. There were significant decreases in the mean gray value, skewness, kurtosis and entropy of the lesions, while there were significant increases in the standard deviation, angular second moment, and inverse difference moment of the lesions after the treatment(P < 0.05). There was no significant difference in contrast between pre-and posttreatment(P > 0.05). A subgroup analysis of PFS showed a significant difference in Δ inverse between the two groups(P < 0.05). Conclusion:CT texture analysis may be helpful for the evaluation of short-term effect to gefitinib-based treatment and the prediction of PFS in patients with lung adenocarcinoma.

Diagnostic Value of CT Coronary Angiography Combined with MMP-10 and F-ABP in Myocardial Infarction

ZANG Yanwei, ZHANG Jing

2020, 29(4): 481-487. doi: 10.15953/j.1004-4140.2020.29.04.11

Abstract(243) PDF(9)

Abstract:
Objective:To explore the diagnostic efficacy of dual source CT coronary angiography combined with serum MMP-10 and F-ABP levels(combined diagnosis) for new acute myocardial infarction(AMI). Methods:62 patients with AMI and 60 patients with non AMI cardiovascular disease were enrolled in the Department of Cardiology of our hospital. The levels of MMP-10 and F-ABP were detected by dual source CT coronary angiography. Based on the results of coronary angiography, the diagnostic efficacy of dual source CT coronary angiography combined with serum MMP-10 and f-abp was analyzed. Results:the levels of MMP-10 and F-ABP in the case group were higher than those in the control group[(8.32 ±0.26) μg/L vs(5.95 ±0.39) μg/L,(8.59 ±2.34) μg/L vs(4.21 ±1.25) μg/L, P < 0.05]. 56 cases of AMI were correctly diagnosed by dual source CT. ROC analysis showed that dual source CT, serum MMP-10, F-ABP and AUC were 0.910, 0.843 and 0.772 respectively. The sensitivity and specificity of dual source CT were 90.32% and 88.33% respectively. The sensitivity and specificity of MMP-10 in the diagnosis of AMI were 79.03% and 83.33% respectively. The sensitivity and specificity of F-ABP in the diagnosis of AMI were 83.87% and 80.00% respectively. The sensitivity and specificity were 98.39% and 100.00%, respectively. Conclusion:dual source CT coronary angiography, serum MMP-10, F-ABP levels have certain diagnostic efficacy for new AMI, the combined diagnosis is closer to the real results, with higher accuracy.

The Effect of High Iodine Concentration Contrast Media in Crohn's Disease Patients

LI Lu, SHEN Xiaojun, JIE Qian, LIANG Zonghui

2020, 29(4): 488-494. doi: 10.15953/j.1004-4140.2020.29.04.12

Abstract(223) PDF(4)

Abstract:
Objective:The purpose of this study was to discuss the effect of high iodine concentration contrast media in patients with Crohn's disease, by comparing the degree of the image quality of abdominal artery and enhancement of thicken bowel wall by using non-ionic contrast agent of different iodine concentrations. Methods:This study was retrospectively performed in 30 patients with known Crohn's disease from May 2016 to January 2019 who underwent CTE. They were assigned into two groups according to different iodine concentration injection, high-concentration iodinated contrast medium(Group A, 400 mgI/mL) and regular-concentration iodinated contrast medium(Group B, 350 mgI/mL). The bolus tracking technique was used to initiate the arterial phase scan. The degrees of image quality were rated on a 3-point scale for qualitative assessment. The computed tomography values of abdominal aorta and Superior mesenteric artery and intestinal wall enhancement were measured for quantitative evaluation, and CNR was computed. The independent t-test was used to compare outcome variables. Results:Group A had significantly higher scores for vascular enhancement image quality(P < 0.05). The mean Abdominal aorta and Superior mesenteric artery enhancement was significantly higher in group A than in group B during the arterial phases(P=0.025). Relative enhancement value of intestinal wall in arterial phase was(39.25 ±11.99) HU and(30.27 ±11.69) HU, respectively, which group A was high than that of group B. The difference was statistically significant(P < 0.05). The CNR of abdominal vascular overall in group A is higher than group B(P < 0.05). Conclusion:Our study suggests that, in patient with Crohn's disease, an increased concentration of iodine improves the image quality of abdominal vascular and its branches, and contributes to a better enhancement in intestinal wall.

Application Value of Coronary CTA Combined with CMR T1 Mapping in Evaluating Salvable Myocardium in Patients with STEMI

SUN Zheng, ZHAO Li, LIU Zhi, WANG Chen, ZHANG Miao, GAO Yan, LU Jie

2020, 29(4): 495-502. doi: 10.15953/j.1004-4140.2020.29.04.13

Abstract(264) PDF(15)

Abstract:
Objective:Coronary angiography(CTA) and magnetic resonance longitudinal relaxation time quantification(T1 mapping) imaging were used to evaluate the level of vascular reflow after myocardial ischemia and the salvage degree of myocardial reperfusion injury in patients with STEMI. Methods:Thirty patients with STEMI diagnosed clinically(experimental group) and 20 healthy persons who met the inclusion criteria(normal control group) were collected. In the experimental group, coronary CTA and T1 mapping sequence were performed. The level of vascular reflow was evaluated by CTA. The volume of area at risk and myocardial salvage index were measured quantitatively by T1 mapping. The T1 values of different segments of myocardium in the experimental group and the control group were calculated and statistically analyzed. Results:Coronary CTA showed reflow of all LAD, LCX, RCA responsible vessels in the experimental group, and T1 mapping showed that the area at risk of STEMI patients was 30.2 ±8.8(%LV), myocardial core infarction 4.7 ±1.7(%LV), and the myocardial salvage index was 67 ±16%. STEMI patients T1_AAR value(1395 ±108 ms) > T1_remote value(1062 ±93 ms) > T1_NC value(967 ±78 ms)(P < 0.05). However, there was no significant difference in the average T1 value of myocardial segments dominated by the three responsible vessels in the experimental group(P=0.79). Conclusion:Coronary CTA technique and CMR T1 mapping sequence can comprehensively and quantitatively evaluate the salvage degree of myocardial ischemia-reperfusion injury in patients with STEMI, and provide imaging support for clinic.

Application of PET/CT Image Assisted CT Guided Lung Biopsy

SI Haifeng, FENG Feng, FU Aiyan

2020, 29(4): 503-510. doi: 10.15953/j.1004-4140.2020.29.04.14

Abstract(286) PDF(7)

Abstract:
Objective:To explore the application value of PET/CT image assisted CT guided lung biopsy. Method:Retrospective collection of 53 cases of pulmonary puncture under the guidance of PET/CT image assisted by CT in our hospital and 120 cases of lung puncture under conventional CT guidance. Count the basic clinical data(age, gender, emphysema), lesion status(size, location), puncture status(puncture position, depth, satisfaction with material sampling, number of times of sampling), and complication status(bleeding, pneumothorax, implantation, air embolism) and pathological results, statistical analysis. The test level is P < 0.05 with statistical significance. Results:There were statistically significant differences between the two groups of patients with satisfactory results in one material extraction, one puncture and two punctures, P < 0.05. The positive rate of pathological results is statistically different, P < 0.05. There was no statistical difference in clinical and puncture related data and total complications, P > 0.05. Conclusion:Compared with conventional CT-guided lung puncture, PET/CT assisted lung puncture has a higher positive rate of pathological results, and can significantly reduce the number of secondary chest biopsies and reduce the occurrence of complications.

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2020 Vol. 29, No. 4