CT理论与应用研究

CT Image Explanation in Peak Diffraction-Enhanced Imaging

LIU Li, ZHU Pei-ping

2008, 17(1): 1-6.

Abstract(2410) PDF(7)

Abstract:
In X-ray Diffraction Enhanced Imaging (DEI), the extinction contrast in peak CT mode can intensify the boundary of the object, and effectively raise the special resolution of the tomographic image. In this article, a definite physical explanation is given to this intensifying effect. By theoretic calculating and BSRF experimental data processing, it is demonstrated that this extinction contrast leads in CT image a fictitious one-pixel wide round ring with a very high mass density, and thus intensifies the image of edges of the round object.

An Improved Single-Slice Rebinning Algorithm for Helical Cone-Beam CT

CHEN Lian, WU Zhi-fang, ZHOU Li-ye

2008, 17(1): 7-13.

Abstract(2298) PDF(9)

Abstract:
Large pitch was used to speed up scanning in helical cone-beam CT, but its reconstruction remains a challenging problem. The Single-Slice ReBinning method (SSRB), proposed by Noo et al, can obtain high image quality at large pitch, but artifacts appear when pitch is too large for given detector. In this paper, a new approximate reconstruction scheme, i.e. Improved Single-Slice ReBinning method (ISSRB) is described. It modified the key rebinning step of SSRB. Theoretical considerations and reconstruction of simulation data are presented in comparison to SSRB in the paper. Results show that the pitch of proposed method is (1+tan²δ) times larger than that of SSRB for given detector size, and the reconstruction image quality is comparable or even better.

Overview of RP-Oriented CT Image Processing Technology

JIANG Rui-zhi, YUE Xiu-yan, SHI Ting-chun, QIU Jian-hui, SUO Hai-rui, PENG Dong-liang

2008, 17(1): 14-20.

Abstract(2454) PDF(9)

Abstract:
Data modeling in reverse engineering is one of key technologies to realize RP. According to the 2D information of CT image, the edge contour was extracted by the image segmentation and binary image processing. Then the 3D CAD model was reconstructed. 3D physical model was made by reconstructing the 3D CAD model, converting into standard data for RP. It has wide application in the biomedicine domain. Based on the state of the study, the process of CT image reverse model and its application on RP were discussed.

Expounding the Pitch,Thickness,Reconstructing Space of Multislice CT and Influencing the Imaging Quality

ZHOU Ze-jun, HU Yong-sheng, GAO Bin, CHAO Hui-ming

2008, 17(1): 21-26.

Abstract(3365) PDF(18)

Abstract:
With multislice CT appearing, the scanning speed was improved enormously. The images of multislice can be acquired simultaneously by once-through scanning, and sufficient informations were postprocessed. It was important that the scanning parameters were choosed rightly. The article expounds the pitch, thickness, reconstructing space of multislice CT, which influences the imaging quality.

Tomography of the Cross-Hole Electromagnetic Measurements

SHEN Jin-song, SUN Wen-bo

2008, 17(1): 27-40.

Abstract(2303) PDF(7)

Abstract:
The regularized least-squares inversion scheme is used to reconstruct the formation resistivity within boreholes from the tomography of the cross-hole electromagnetic measurements. In the tomography, a two-dimensional conductivity variation profile with point dipole sources and receivers in it are assumed. The forward modeling was fulfilled by the iso-parametric finite element method in wave-number domain, and the 3-D problem was converted to a series of 2-D problems in K_y wave-number domain, thus make it possible to deal with the practical model. For the requisite number of K_y values, the coupled equations are solved by the finite element method on the iso-parametric element on the xoz plane. In order to improve the accuracy of the numeric solution, Gauss integral was applied to the wave-number numeric solution in the inverse Fourier transformation of the wavenumber domain solution to real space domain. The sensitivities of the electromagnetic measurements to the formation conductivity are effectively calculated by using of the reciprocity principle of the electromagnetic fields in source locations and receiver locations. Our method validated by using of the simulation data and field data. For the singularity of the source point in modeling of cross-hole electromagnetic measurement, a pseudo-delta function was adopted to distribute the dipole source current, and the numeric accuracy is enhanced. A quantitative test of accuracy is presented which compares the numeric results with the analytic solutions for a dipole source in layer medium for different wave number K_y to validate the code. Through the perturbation of the conductivity of a single block, the difference between two simulations was compared with that from the reciprocity principle, and the effectiveness has been verified. The sound tomography results of the simple block, slant fracture zones and the big character model, verify the effectiveness of the tomography procedures.

A High Speed Data Transmission Solution for Cone-beam CT Based on Ethernet Interface

JIN Xin, CHEN Zhi-qiang

2008, 17(1): 41-49.

Abstract(2404) PDF(10)

Abstract:
With the fast development of the CT technology, real-time data acquiring and fast image reconstruction as a advanced capability in a Cone-beam CT system are more frequenfly requested. Therefore to transfer projection data from the detector unit to the computing unit in a fast and stable way becomes one of the key points in today's design of CT systems. In this paper we proposed a high speed data transmission solution based on Ethernet interface and Linux OS in which a transfer caching system is introduced. Test results show that such application has significant merits in solving the data loss problem while transferring from CT sampling module to the PC. Being with a low cost yet high stability and efficiency, it can be practically useful to the similar fast data acquiring system for image reconstruction.

Study on the Application of ICT to Structure Analysis and Dismantle in the Aerial Depth Bomb

SUN Ming-tai, LIANG Yue-xuan, HU Zhu-xi, XU Jian-hua

2008, 17(1): 50-55.

Abstract(2178) PDF(3)

Abstract:
Through the analysis of the research technique of Reverse Engineering, this article has put forward a kind of method. The method is using the industrial computer tomography (ICT) fault scan to carry out structural analysis on the Aerial Depth Bomb, and accurately measure its component location, dimension changes. Then draw the blueprint and establish the dismantle scheme accordingly. Consequently, it has offered security and reliability for the dismantlement and study of the depth bomb.

The Findings of Multi-Slice CT in Pripheral Pulmonary Hamartoma

BI Chun-long, WAN Xia, ZHANG Wei

2008, 17(1): 56-60.

Abstract(2450) PDF(6)

Abstract:
Objective: To research the appearances of multi-slice CT(multi-slice CT MSCT)in pulmonary hamartoma so as to improve the CT diagnostic accuracy. Methods: The CT and pathological findings of 32 cases of pulmonary hamartoma were analyzed. Dynamic contrast enhancement MSCT scanning were performed in 22 cases. All cases were confirmed by surgical operation and pathology. Results: All hamartomas had smooth edge on MSCT. Focal fat without calcification inside were present in 12 of 32 cases(37.5%), focal fat and calcification inside in 8 of 25cases (25%), calcification without fat inside in 2 of 32 cases (6.25%). The CT contrasted value was less than 20 Hu in 20 of 22 cases (90.9%). Contrast-enhancing septa were present in 16 of 22 cases(72.7%). Conclusion: Some specific MSCT features, including smooth edge, calcification and fat inside, are useful for diagnosis of pulmonary hamartoma. Dynamic contrast enhancement MSCT scanning is useful for differentiating pulmonary hamartoma with peripheral lung carcinoma.

The CT Diagnosis and Clinical Analysis of Neonatal Hypoxic-Ischemic Encephalopathy

DENG Jia-xiu, ZHANG Yong-dong

2008, 17(1): 61-66.

Abstract(2173) PDF(2)

Abstract:
Objective: To discuss CT characteristic and clinical manifestation of hypoxic-ischemic encephalopathy (HIE). Methods: Combined with CT manifestation, the clinical materials of 85 HIE patients were analyzed retrospectively. Results: According to the clinical diagnosis criterion of HIE, the patients in this sequence were divided into three groups, mild group (26 cases), moderate group (38 cases), severe group (21 cases). At CT imaging, there was low density area of brain in 85 cases, CT value was from 6 to 18Hu, combined with high density hemorrhage of 52 cases, which CT value was about 58 to 85Hu. According to the CT diagnosis criterion of HIE, in three groups (mild, moderate and severe group) were 26, 38, and 21 cases, respectively. Out of all cases, 48 cases were performed fellow-up CT examination in latter, 19 cases of hydrocephalus in mild group became normal in 11 days, 12 cases of the hydrocephalus in moderate group were lightened and disappeared, and subarachnoid hemorrhage were absorbed. A little subdural effusion was appeared in one case. In severe group, out of 17 cases, there was 6 cases of encephalomalacia, 3 cases of brain atrophy and subdural effusion, 2 cases of waterhead, 2 cases of calcification, 1 case of porencephalic cyst, 4 cases dead. Conclusions: Cranial CT could show the brain lesions of neonatal HIE, according to CT manifestation of HIE, it was consistent with clinical criterion. Re-CT examination could show the change of this cranial disease. Combined with clinical manifestation, the examination of cranial CT has important value for diagnose and intervene, and decrease the sequela of this disease.

Evaluation of Multislice Helical Computed Tomography in Diagnosing of Duodenal Diverticulum

ZHANG Jian-mei, ZHAO Tong, WEN Ting-guo

2008, 17(1): 67-71.

Abstract(2238) PDF(6)

Abstract:
Objective: To discuss the value of MSCT in diagnosis of duodenal diverticula. Methods: Twenty-three patients suspected duodenal diverticula with MSCT were examined with GI in one week. Results: Twenty-two cases were detected with MSCT and GI, detection rate is 95.6%(22/23), Duodenal diverticula appeared cystiform nodose lesion, whicn were outstanding duodenum and had air-flind level or netting image. Conclusion: MSCT is rapid and safe method, it can be provide more diagnostic information.

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2008 Vol. 17, No. 1