CT理论与应用研究

A New 3D Iterative Reconstruction Algorithm for C-Arm Imaging Systems from Limited-Angle Cone Beam Projections

WANG Li-yan, LUO Shou-hua, WEI Zhi-hui

2008, 17(4): 1-7.

Abstract(1173)

Abstract:
In this paper,a new 3D iterative reconstruction algorithm for C-arm imaging systems from limited-angle of cone beam projections was proposed.The well-known FDK algorithm was adapted for C-arm imaging systems.Our approach was to introduce prior knowledge and regularizations(such as non negative,limited support) into iterative procedure.Experiments show that by our method,the streak artifacts can be greatly suppressed and the contrast can be significantly improved.

CT Reconstruction Algorithms with Sparse Radiographs Based on Bayes Estimates

XIE Dan-yan, JING Xi-li, REN Guo-chao

2008, 17(4): 8-14.

Abstract(840)

Abstract:
A Bayes estimation method is presented via analyzing CT reconstruction with sparse radiograph data.We transform prior information about target object based on medical treatment anatomy to prior probability density and measurement information to likelihood function,and combine them to get posterior probability density.Through sampling and mean estimates,the expected value is taken as the result of CT reconstruction.The simulation results show that,compared to conventional CT reconstruction methods,the Bayes estimation method has less radiation data,short reconstruction time,good-quality images and high noise resistance.

CT Reconstruction Algorithm from Limited-angle Using Modified Regularization Method

WANG Hao, LU Xiao-qiang, SUN Yi

2008, 17(4): 15-22.

Abstract(1041)

Abstract:
In this paper, a modified Tikhonov regularization CT image reconstruction algorithm from limited-angle was proposed.The modified Tikhonov regularization method adopted homotopy mapping to adjust the regularization parameter continuously, which increased the efficiency of computation procedure by avoiding the attempt of the regularization parameter.Experimental results show that the proposed algorithm improved the quality of reconstruction image by fixing on the optimization parameter rapidly.

Review on Reconstruction Algorithms for Differential Phase-Contrast Computed Tomography

FANG Qiao-guang, ZHANG Li, HUANG Zhi-feng, CHEN Zhi-qiang

2008, 17(4): 23-31.

Abstract(958)

Abstract:
Based on the principles of diffraction enhanced imaging(DEI) and grating-based phase-contrast imaging,the reconstruction algorithms for differential phase-contrast CT(DPC-CT) are discussed,including the latest developments,the main ideas and their properties.These algorithms are combination between the physics principles of phase-contrast imaging and conventional CT reconstruction theories,which can reconstruct the distribution of refractive index decrement in the sample from differential projection data directly,showing the interior structure of the low-Z weakly absorbing materials.

The Earthquake Volume from Body Waves

Seweryn J. Duda, Jaromír Janský

2008, 17(4): 32-46.

Abstract(932)

Abstract:
The propagation of seismic body waves is a linearly elastic process in most of the Earth body.Only in the region surrounding the earthquake focus nonlinear processes may be expected to take place as the result of the radiation and propagation of the waves.The investigation is concerned with the estimation of the dimension of the region in which nonlinear processes prevail.

A Preliminary Application Study of the IP Sounding Method in Luoning Qiliping Multi-Metalliferous Ore Exploration

CHEN An-wen, LI Qing-lin, YU Yi, XU Shun-qiang, XIE Ru-yi, ZHANG Wei-dong, GAO Wei, YANG Chen-tang, ZHANG Zhen-yu

2008, 17(4): 47-54.

Abstract(915)

Abstract:
The application of IP sounding technology has made geophysical prospecting more simple, highly efficient and economical.This paper presents a preliminary study and the application result of the IP method in Luoning Qiliping multi-metalliferous ore exploration.The principle and usage of the method have been discussed and, in particular, the paper elaborates on the technical principle and scientific basis, equipment and data acquisition, observation instrument and system control, data processing and tomography algorithm, polarization mode and parameter computation, technical characteristics and precautions for applying the IP technology to mineral resource exploration.

Application of CV Active Contour in Weld Defects Detection

LI Shou-tao, CHEN Hao, ZHU Rui-hui, LI Xiao-mao

2008, 17(4): 55-61.

Abstract(947)

Abstract:
Weld is the main way of constructing steel structure.X ray detection is one of the few major techniques in detecting weld defects.There are two methods for evaluating the results of X ray detection: manually and automatically evaluation.In a manual way,the person may be tired so the result is not reliable,and the evaluation is subjective.The computer aided analysis and recognition can improve the efficiency.The basis of analysis and recognition is image segmentation.This article is based on CV model which is an development of Mumford-Shah model and active contour by Tony,Chan and Luminita.And we apply this model in welding seam defects detection.

Contour Data Denoise Based on Inter-Scale Correlations of Contourlet Transform

DONG Fang, HU Liang, LI Bo-lin, LI Ming, CHEN Hao, WANG Yuan, ZHANG Cheng-xin, XU Zhou

2008, 17(4): 62-66.

Abstract(918)

Abstract:
Because CT slice outline data has a lot of noise,, proposed the multi-scale analysis method based on the curvature wavelet transform. Using the inter-scale correlation to achieve denoise and features detection. Not only solved the single-scale can not effectively remove contour noise, but also solved the contour detection difficult and the poor fitting accuracy problems which were caused by sharp fluctuations of line features.

Study of Medical Gray Level Normalization Technique

WAN Jin-xin, SONG Yu-qing, DONG Shu-de, ZHAO De-kun

2008, 17(4): 67-75.

Abstract(1119)

Abstract:
The current paper describes processing of liver images via histogram equalization,Wiener filtering and median filtering.The gray level transformation technique was used for gray adjustment of the images after the processing.The images are put together and an analytical comparison is carried out for quality evaluation.The innovative gray level transformation technology after median filtering yields exquisite images,with clear tissue structure and stronger layered effect in the interest area,and thus it is significant to clinical diagnosis.The technology can attain gray level normalization display without manual adjustment of the window breadth,which facilitates computerized automatic identification.

Study of Clinical Applied Characteristics of 3.0T MRI

CHANG Ren-min, LIU Guang-bao, ZHANG Yu-zhong, HU Ba-sheng, CHEN Bin, QU Hua-li, XU Yi-kai, QIU Shi-jun, ZHANG Xue-lin

2008, 17(4): 76-81.

Abstract(840)

Abstract:
In order to conduce to comprehend some basic physical knowledge,to congnition accurately clinical practical value of 3.0 T MRI,to foster strengths and circumvent weaknesses and bring it into full play in clinic and scientific research,the characteristics,advantage and disadvantage is studied and analyzed in signal noise ratio(SNR),susceptibility effects,dielectric effects,chemical shift effects,relaxation time and specific absorption rate(SAR).

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2008 Vol. 17, No. 4