CT理论与应用研究

Energy Shaping Theory and Simulation for Electron Linac X-ray Source

ZHANG Yu-long, CHEN Huai-bi, ZHA Hao

2014, 23(1): 1-8.

Abstract(841) PDF(3)

Abstract:
Energy shaping technology could be used to reduce artifact error and increase nondestructive testing accuracy.How to produce required spectrum is a key issue.This article proposes spectrums whose peak energy are 3 MeV,6 MeV and 12 MeV especially as required spectrum and discusses calculation method for energy shaping.In order to calculate related parameters,this article simulates X-ray spectrum produced by electron Linac with Monte-Carlo method,makes equation fitting for the X-ray spectrum and linear attenuation coefficients of shaping materials,decides final arrangement for shaping according to calculation results and verifies the arrangement with Monte-Carlo method.

Diagnostic Value of Hypertrophic Cardiomyopathy by Dual-source CT Functional Imaging

CHENG Guan-xun, YAN Jing, LIU Guo-shun, YU Kang-hui

2014, 23(1): 9-17.

Abstract(711) PDF(3)

Abstract:
Objects:To evaluate the clinical application value in the assessment of HCM by dual-source CT(DSCT).Methods:The clinical dada and DSCT imaging of 10 cases with confirmed HCM and 13 normal controls were analyzed retrospectively.Results:10 cases of HCM including asymmetric HCM(n=9),symmetric HCM(n=1) were clearly diagnosed by DSCT,and one of asymmetric HCM was accompanied by LVOT.The thickness of interventricular septum,anterior wall and apical in the HCM group were significantly greater than in the control group,while there were no significant differences in the thickness of free and posterior wall between them.The ratio of maximum wall thickness of the Left ventricular wall or apex to the PWTd in end-diastole was greater than 1.5 in the HCM group.LVIDd,LVIDs and LVOTd in the HCM group were smaller than in the control group,on the contrary,LADd in the HCM group was greater than in the control group.WT in the control group was about(57.88 5.09)%,while it reduced to(20.10 ± 4.89)% of the thickened segments in HCM group.Both MM and EF in the HCM group were greater than in the control group,instead,both EDV and ESV in the HCM group were smaller than in the control group.One case had atheromatous plaque and the degree of coronary artery stenosis was approximately 85%;7 cases had myocardial bridge(MB) and all of the MB at LAD.Conclusions:DSCT is a promising modality to assess HCM,which can provide one-stop noninvasive evaluation of cardiac morphology,function,as well as coronary artery anatomy.

Research on Inspecting Concrete Flaws with LFM Signal

LI Zhang-zheng, SHI Fang-fang, WU He-zhen

2014, 23(1): 19-26.

Abstract(723) PDF(1)

Abstract:
On account of existing problems of ultrasonic inspecting concrete defect,such as low signal noise ratio(SNR) and limited penetrating depth,the method of exciting with LFM is put forward.Linear frequency modulation(LFM) signal with the characteristics of long time series and wide band width is excited at transmitting terminal,and compressed signal with narrower main lobe and higher SNR will be obtained at receiving terminal through compression method.The effect of transducer's bandwidth is analyzed.The results of numerical calculation show that good compressed results of echo will be obtained if there is much noise.Testing results show that pulse compression method can improve signal-noise ratio.

Suppressing Method Study and Application of Seismic Scattered Wave Based on Local Hyperbolic Radon Transform

WANG Li-xin, HUANG Guang-tan, ZHANG Bin-bin, ZHU Wen-bo, ZHANG Jun-hua

2014, 23(1): 27-36.

Abstract(729) PDF(1)

Abstract:
Generally,seismic waves scatter when they meet a subsurface heterogeneous body,i.e.a scattering source.Currently,scattered imaging technique which uses scattered waves as effective waves has been used in the identification of special geologic bodies such as caves and fractures.However,in the Gobi Desert,gravel areas,mountain front and other surface complex areas,scattered waves affect the quality of seismic data seriously and are interference waves for seismic field data.Because related research and practical application are not clearly seen at home and abroad,it is necessary to analyze basic characteristics and study denoising method of scattered wave.Firstly,this paper analyzes the geometric characterization of reflection wave and scattered wave based on the t-x relationship in seismic kinematics.Then,finite difference method is applied to simulate scattered wave field and local hyperbolic Radon transform method is proposed to suppress scattered wave for theoretical models.For field CSP data,the limitation of FK filtering to denoise scattered wave is analyzed and then local hyperbolic Radon transform technology is used to remove scattered wave on shot gathers,the results show that scattered wave obtains effective suppression using this method.

The Relationship between the Optimal Magnification and the Limit Spatial Resolution in CT System

CHEN Jian, HUANG Zheng-ren, LIU Xue-jian, YANG Jin-jing, CHEN Zhong-ming, LIU Yan, YUAN Ming, ZHU Yun-zhou

2014, 23(1): 37-43.

Abstract(832) PDF(8)

Abstract:
The faithfulness of a CT image depends on a number of system-level performance factors,with one of the most important being spatial resolution.Spatial resolution refers to the ability of a CT system to resolve small details or locate small feature with respect to some reference point.Spatial resolution is generally quantified in terms of the smallest separation at which two points can be distinguished as separate entities.The limiting value of the spatial resolution is determined by the design and construction of the system.The limit spatial resolution is determined by the cut-off frequency(COF),which is approximately 1/BW.The optimal magnification is derived by the relationship equation in this paper.This discovery of this principle will be helpful to getting the best image for the testing personnel in his work.At the same time it will also provide a theoretical basis for the design of the CT system.

CT Image Binarization Threshold Selection of Coal and 3D Reconstruction Technology Research

ZHANG Qing-cheng, WANG Wan-fu, ZUO Jian-min, MAO Ling-tao, LIU Dian-shu

2014, 23(1): 45-51.

Abstract(706) PDF(2)

Abstract:
Completion of the uniaxial loading experiments using industrial CT experimental system of coal samples(DT-3),and carried out a series of coal specimen tomography,accessed to the different cross-sections at the destruction of CT images.Based on image segmentation technology,the image gray level set different binarization threshold,the threshold under different pore size change curve,and puts forward to a turning point in the corresponding threshold as a slit image binarization threshold.By the threshold and the gray linear weighted average method,the coal is realized the 3D reconstruction of CT images by the Matlab software programming,and it providies a scientific basis in order to study of coal fracture 3D representation.

Rayleigh-wave Tomography Based on Ambient Seismic Noise in the Central and Western Blocks of the North China Craton

SHI Cheng-cheng, LU Lai-yu, WANG Chun-yong, HE Zheng-qin, DING Zhi-feng

2014, 23(1): 53-64.

Abstract(782) PDF(4)

Abstract:
Using the one-year ambient noise records of 51 portable broadband stations across the Ordos Block and 138 permanent stations from May 2010 to April 2011 with data of the North China Array during the year of 2007,we obtained Rayleigh wave group velocity maps in the Central and Western Blocks of the North China Craton from 6s to 36s based on ambient seismic noise tomography.The results for 6s to 15s show the outline of tectonic units in the upper crust,such as rises and collapse basins;the results for 16s to 30s indicate the possibility of low-velocity zones within the middle and low crust of the Datong Basin and the western area of the Fenhe Basin;the results for 30 s to 36 s show that the thickness of the crust in the Eastern Block is thinner than that in the Central and Western Blocks,and the Moho depth of some collapse basins is respectively shallower compared with that of adjacent regions.

Analysis of Stratigraphic Resolution with the Current Parameter in Electric Logging

QIANG Jian-ke, XIAO Jun-ping

2014, 23(1): 65-70.

Abstract(704) PDF(2)

Abstract:
In the conventional electrical logging,the apparent resistivity of wall rock is calculated by the electric current and the potential difference between electrodes.As the same time,the stratigraphic interfaces are divided by the apparent resistivity.However,the current parameter is often ignored.In this paper,we could get the resistance change of the wall rock by the change of the electric current based on the ohm's law.And then we identify the stratigraphic properties by the current intensity curve.Theory analysis and experiment show that the current of the electrode depends on its contact resistance,but the apparent resistivity depends on the sizes of the two receiving electrodes or the electric array,that is the integrated result.So the sensitivity of current logging curve is higher than the apparent resistivity's.The layer interface can be accurately divided with the current intensity of logging curve and the thickness of strata is determined.It is attractive because almost free cost.

Application of Seismic Waveform Classification Technique in the Study of Fluvial Reservoir

FAN Hong-jun, FAN Ting-en, WANG Hui, GAO Yu-fei

2014, 23(1): 71-80.

Abstract(685) PDF(1)

Abstract:
The technology of seismic waveform classification technique is very mature,but it is not perfect in the oilfield development.The reservoir of fluvial facies that changes very quickly on the side has a severe heterogeneity,so it is a critical problem to descript the reservoir heterogeneity between wells.Through the combination of logging and 3D seismic data,using the seismic waveform classification techniques,by the bridge of electrofacies,the seismic waveform characteristics can be turn into the reservoir overlay feature that improves the description of the reservoir distribution heterogeneity.Studies have shown that:the fluvial reservoirs has the typical four electrofacies types corresponding to four kinds of seismic response characteristics,that represents the fluvial reservoir overlaying mode.The application of seismic waveform classification techniques supplies the support of well locations adjusting of and potential reserves searching in the development oil field.

The Application of Seismic CT Technology in Urban Geological Survey

GUO Shu-jun, HOU Yan-hua, LI Hong-li, LEI Ming, LIU Wen-zeng

2014, 23(1): 81-90.

Abstract(710) PDF(2)

Abstract:
In order to successfully apply seismic computerized tomography(CT),at first,the author used cross-hole imaging method to get the first break travel time data.Then,on the processing basis of curved ray-tracing forward modeling based on shortest path method and inversion technique based on LSQR algorithm,combined with well logging data interpretation,the author got the cross-hole wave velocity distribution maps.Thus,within the scope of well control,the stratum structure and the foundation grouting effect were studied.Also,the locations and distributions of fracture tectonic belt and people shelter were gotten.This result shows that when seismic CT is used in urban environmental geological survey and evaluation and shallow engineering geological investigation,it can solve the complexity of formation lithology and structure and accurately predict the target environment.Seismic CT plays an important role in urban environmental geology research and in the construction of infrastructure and has important significance to promote the development of urban geophysical prospecting technique.

Computer Simulation of Digital Projections-of-cuboid Object in CL System

WANG Ya-xiao, WEI Cun-feng, QUE Jie-min, SHU Yan-feng, CAO Da-quan, WANG Yan-fang, SUN Cui-li, SHI Rong-jian, WEI Long

2014, 23(1): 91-100.

Abstract(701) PDF(2)

Abstract:
Computer Simulation of X-ray Projections can be used to exclude the random errors during the X-ray tomography scan.It can be used for verifying the correctness of the scan mode and image reconstruction method,and providing theoretical basis for the actual system implementation and improvement and reconstruction algorithm.While most of the simulation focused on cylinder and ellipsoid,we make simulation of cuboid samples in typical CL system in this paper,as printed circuit is approximate sheet-like cuboid.We compared the Experimental and simulation results and get satisfactory results.The work provides a good foundation for improving image reconstruction algorithm,analyze errors and correct artifacts.

High Atomic Number Liquid Container Identification Based on Combined Invariant Moments and Local Feature

XU Yu-jun, YANG Li-rui

2014, 23(1): 101-113.

Abstract(704) PDF(2)

Abstract:
For the security inspection at airports and stations,it is urgently needed to discriminate the liquid examination.We proposed a novel method for high atomic liquid container discrimination based on global and local features.First,we extracted the combined invariant moments based on the global feature,which quickly find a large number of candidates for an efficient recognition.Then local feature identification was made as a second judgment to improve the recognition accuracy of feature detection.The container wall the bottom projection features were chosen as the local feature.Experimental results show that this method combines good global and local target information.This approach can solve the container occlusion problems with a high atomic number materials in partial,and also has high recognition accuracy.

A Fast Simulation Method for CT Projection Based on Bisection

LI Bin, ZHANG Yao-jun, ZHU Pei-ping, LI Bao-lei, MO Yang

2014, 23(1): 115-122.

Abstract(724) PDF(1)

Abstract:
Projection simulation is the basis of CT simulation research.A fast simulation method for CT projection based on bisection was proposed in this paper,and then the simulation process was optimized.As long as a scanned object could be decomposed to individual convex items,arbitrary scanning trajectory could be used to simulate projection based on our method,and the projection accuracy could be infinitely close to theoretical projection accuracy.Numerical simulation results verify the effectiveness of our method.

Preliminary Study of Diagnostic Value of Ultra High Resolution Thin Slice CT on Small Pulmonary Nodules Diameter Less Than 2cm

ZHANG Ming-xia, WANG Ren-gui

2014, 23(1): 123-130.

Abstract(1004) PDF(2)

Abstract:
Objective:Morphological features of solitary pulmonary nodules is an important basis to judge the malignant and benign,high resolution CT imaging is a key factor to improve the detection rate of SPN subtle morphological characteristics.The objective of this study is to comparatively analyze the difference of pulmonary nodules diameter less than 2 cm imaging features between high resolution thin slice CT(512×512 matrix,HRCT) and ultra- high resolution thin slice CT(1 024×1 024 matrix,ultra-HRCT),and to analyze the advantages and disadvantages of ultra-HRCT in showing the fine structure of SPN and the image quality.Method:72 SPN in living body were scanned by ultra-HRCT and HRCT.The occurrence rate of various features of SPN was calculated,the features of SPN include:edge:lobulated sign(deep,shallow),halo sign(clear,fuzzy),burr sign(thin and short burr,thin and long burr,spine sign),internal structure(bubble sign/air bronchogram/cavity),nodules density(calcification,ground glass density).Meanwhile the image quality of ultra-HRCT and HRCT was observed,and their statistical difference was analyzed.Results:The occurrence rate of various features of SPN prompts that ultra-HRCT is better than HRCT,but P>0.05,which showed no significant statistically difference.The image quality of ultra-HRCT is better than that of HRCT,but P>0.05,which showed no significant statistically difference.Conclusions:The occurrence rate of various features of SPN on ultra-HRCT is less than that on HRCT,ultra-HRCT on the lobulated sign,burr sign,halo sign,bubble sign,air bronchogram,the detection rate of GGO is higher than that of HRCT,suggesting that ultra-HRCT in displaying the lobulated sign,burr sign,halo sign,bubble sign,air bronchogram,GGO and other fine is better than HRCT in terms of structure,but the two has no significant statistical difference.Subjective image quality score of HRCT was higher than Ultra-HRCT,ultra-HRCT image display quality is better than that of the edge of the lesion and vascular structure of HRCT,but the motion artifacts and noise occurrence rate is higher,the difference was not statistically significant.X-ray radiation dose of the two are in a safe range.

The Diagnostic Value of Quantitative T1WI MR Parametric Perfusion-weighted Imaging Based on DCE-MRI in Duct-borne Breast Cancer

YAO Wei-wei, XIA Jun, DU Heng-feng, LIU Pin-ni, LUO Xiao, LEI Yi, LIN Fan, WU Hui-sheng

2014, 23(1): 131-138.

Abstract(734) PDF(9)

Abstract:
Objective:To study the diagnostic value of quantitative T1WI MR parametric perfusion-weighted imaging based on DCE-MRI in duct-borne breast cancer.Methods:16 cases of female were performed the DCE-MRI examination before surgical operation,and the time-intensity curve(TIC) were acquired,then the parameters perfusion images of Wash-in,Wash-out,TTP,MIPt and PEI were drawn out by the special software for breast.And then measured the parameters of perfusion,analyzed the features of perfusion of duct related breast cancers.Results:13 cases invasive ductal carcinoma and 3 cases ductal carcinoma in situ were confirmed by pathology in the 16 cases.13 cases were non-mass-like enhancement,such as 7 cases duct-like,5 cases patchy,1 case spot-like.Another 3 cases were mass enhancement.All of the 16 cases TIC were the type II.13,10,9,15 and 16 lesions were found in the five kinds of parametric images.The detection rates were 81.25%,62.50%,56.25%,93.75% and 100%,respectively.We found the parameters between lesions and normal breast tissue were significant difference(P<0.001).Moreover,the parameters between periphery and centre of lesions was also significant(P<0.001),except in the TTP.But there's no significant difference between the invasive ductal carcinoma and the ductal carcinoma in situ.Conclusion:Quantitative T1WI MR parametric perfusion-weighted imaging based on DCE-MRI has a high detection rate of the duct-borne breast cancers,and might provide important additional information for its diagnosis and differential diagnosis.

The Low Field MRI Findings of Iliotibial Band Friction Syndrome

DING Zhang-qing, WANG Wen-sheng, WANG An-zhen, LI Hai-feng, DENG Hong-zhen, SUN Ying-ying, LUO Hui, DAI Lan-lan

2014, 23(1): 139-144.

Abstract(666) PDF(3)

Abstract:
Objective:To explore the low field MRI features of the iliotibial band friction syndrome(ITBFS).Methods:The clinical and 0.35 T MRI imaging data of 12 patients with ITBFS lesions confirmed clinically were analyzed retrospectively.Results:All patients had lateral knee pain,particularly evident when running and other sports.On the acute and sub acute stage(4 cases),MRI showing the iliotibial band swelling with the increased signal,the swelling effusion located in the medial and(or) lateral of the iliotibial band;On the chronic phase(8 cases),MRI showing the thickening iliotibial band,the swelling effusion located in the medial and(or) lateral of the iliotibial band may be seen.The coronal MR imagings show the best.Conclusion:Knowing the features of clinical and low field MRI manifestations may be helpful to early diagnosis of the ITBFS.

Quantification of Epicardial Adipose Tissue in Non-ECG-gated Low-radiation-dose MDCT

WU Lei, ZHA Yun-fei, LIU Chao, CHEN Wen, CHEN Yi-jia

2014, 23(1): 145-152.

Abstract(651) PDF(2)

Abstract:
Objective:To quantify the EAT volume in non-ECG-gated low-radiation-dose MDCT and assess the relationship of EAT volume in non-ECG-gated MDCT in comparison with ECG-gated Coronary CTA.Method:In all,61 patients were enrolled in this study and underwent retrospective ECG-gated coronary CTA and non-ECG-gated low-radiation-dose MDCT for lung cancer screening.The EAT volume was calculated through depicted the epicardium with AW4.4 workstation(GE).The threshold of EAT quantification in non-ECG-gated CT was -195~- 45 Hu.A total of five programs of the thresholds of EAT quantification in coronary CTA would be built(-175~- 25 Hu,-170~- 20 Hu,-165~-15 Hu,-160~-10 Hu,-155~- 5 Hu respectively).Result:The EAT volume quantification in non-ECG-gated MDCT had a significant relationship with the quantifications in ECG-gated Coronary CTA(r=0.996,r=0.997,r=0.997,r=0.997,r=0.996 respectively).When the threshold of EAT quantification in ECG-gated Coronary CTA was -165~-15 Hu,no significant difference was observed for EAT volume quantification with non-ECG-gated MDCT with respect to ECG-gated Coronary CTA(P=0.125).Conclusion:Non-ECG-gated low-radiation-dose MDCT allows quantifying EAT with almost the same consistency and correlation as using ECG-gated Coronary CTA.

The Value of MSCT and Post-processing Techniques in the Diagnosis of Abdominal External Hernia and Intestinal Obstruction

CHEN Wen, CHEN Yi-jia, FU Chuan-ming, CHEN Ping-you, GONG Xiao-hong

2014, 23(1): 153-158.

Abstract(672) PDF(1)

Abstract:
Objective:to assess the value of MSCT and post-processing techniques in the diagnosis of abdominal external hernia and intestinal obstruction.Methods:CT features of 21 cases with abdominal external hernia and intestinal obstruction confirmed by surgery were retrospectively analyzed.19 cases underwent abdominal plain and two contrast scans.MPR and CPR post-processing techniques were performed in all patients.Result:21 cases abdominal external hernia and intestinal obstruction were confirmed,of which 8 cases with oblique inguinal hernia,5 cases with direct inguinal hernia,4 cases with incisional hernia,2 cases with Cloguet's hernia,2 cases with obturator hernia;13 cases with incomplete intestinal obstruction,8 cases with complete intestinal obstruction.Conclusion:MSCT and post-processing technique is valuable for diagnosing abdominal external hernia and intestinal obstruction,which can provide accurate and reliable information for the surgical plan.

The Comparative Study of CT and Pathology in Intra-abdominal Desmoid Tumors

LIU Huan-huan, ZHANG Huan, PANG Li-fang, SHI Lei, PAN Zi-lai, CHEN Xiao-yan, CHEN Ke-min, YAN Fu-hua

2014, 23(1): 159-165.

Abstract(742) PDF(1)

Abstract:
Objective:To investigate the CT imaging and pathology features of intra-abdominal desmoids tumors(DT).Methods:CT imaging features of 10 cases with intra-abdominal DT proved by pathology were retrospectively reviewed and compared with pathological results.Results:Among the 10 cases,6 cases were located in the abdominal cavity and 4 cases in the retroperitoneum.The maximum tumor size ranged from 4.3 to 17.1 cm.4 cases were irregular and 6 cases were ellipse.5 tumors had well-defined contours,the other 5 cases showed ill-defined contours.3 cases showed complete or incomplete encapsulation.All the 10 cases underwent CT plain and enhanced scan.On CT plain imaging,the lesions showed homogeneous density in 3 cases,the others showed heterogeneous density,one of which had flaky hemorrhage.There was no necrosis or calcification in all lesions.All the tumors showed lower density than iliopsoas.On CT enhanced scan,10 lesions presented slight heterogeneous enhancement in the arterial phase and continuous enhancement in the venous phase.Under the microscope,the spindle fibroblasts were bunchy distribution with no obvious heteromorphism and rare karyokinesis.The collagen fibers showed proliferation and mucinous degeneration.Positive immunohistochemical staining:Vimentin 100%(10/10).Negative immunohistochemistry staining:CD34 90%(9/10),S-100 90%(9/10),CD117 100%(10/10),SMA 80%(8/10).Conclusion:Intra-abdominal DT has characteristic features on CT imaging and plays an important role in the diagnosis and distinction between DT and other tumors in abdomen.

The Diagnostic Value of Multislice CT in Retroperitoneal Parasitic Foetus

FU Chuan-ming, WU De-hong, GONG Xiao-hong, XU Jian, CHEN Lun-gang, XU Lin, XIONG Yin

2014, 23(1): 167-172.

Abstract(658) PDF(1)

Abstract:
Objective:To evaluate retroperitoneal parasitic foetus of MSCT axial images and image post- processing performance,further improve the understanding of the disease inspection method.Methods:2 cases of clinical suspected diagnosis of retroperitoneal parasitic foetus with MSCT scan first,then the original image to AW workstation 4.2 a thin layer of multiplanar reconstruction(MPR),volume representation(VR) and maximum density projection(MIP);Observation of axial,MPR,VR,MIP imaging characteristics.Results:2 cases of axis of probably have shown in the image to see a mixed density with irregular shape,clear boundary,which see liquid,fat,bone,soft tissue density with post processing image in the spine,pelvis,and part of limbs.Conclusion:MSCT post-processing techniques of retroperitoneal parasitic has high diagnostic value,especially VR can directly provide parasitic foetus imaging characteristic.

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2014 Vol. 23, No. 1