CT理论与应用研究

Fast Computation of 3D Radon Transform Via a Geometrical Method

XU Hai-jun, WEI Dong-bo, FU Jian, ZHANG Li-kai, DAI Xiu-bin

2008, 17(2): 1-7.

Abstract(2977) PDF(19)

Abstract:
Exact three-dimensional reconstruction algorithms are usually based on the three-dimensional Radon transform which is also widely used in other related fields. However, Radon transform consists of all Radon values placed at the corresponding points. Each value is defined as a plane integral in the object domain. So, the computation of Radon value is rather time expensive using direct integral method. New applications based on it may become convenient if a fast and efficient transformation algorithm is adopted. Therefore, an analytical method is proposed to compute the 3D Radon transform in this paper that is based on 3D S-L phantom including spheres and further compare it with the traditional algorithms of their advantages and disadvantages. Finally, the origin object reconstructed by 3D inverse Radon transform has been proved right by the result from computer simulation.

Registration of Three Dimension Digital Model and CAD Model Based on the Method of Adaptive Genetic Algorithm

HU Dong-cai, ZHAO Xin-bo, ZHANG Ding-hua, LI Ming-jun, KONG Yong-mao

2008, 17(2): 8-14.

Abstract(2336) PDF(6)

Abstract:
To match the three dimension digital model and the CAD model, a new method is proposed, which consists of the surrounding box -based initial registration and the float data coded adaptive genetic algorithm-based accuracy registration. The initial registration can ensure the ranges of the spatial transform parameters for the accuracy registration. In the accuracy registration, the goal function is constructed by the method of the least squares. In order to overcome the premature convergence, an index that is related with the diversity of the population is defined. The index is used to define the crossover operator and mutation operator in the genetic algorithm, and to adjust the probabilities of the crossover and mutation adaptively. The result showed that the method can properly match the three dimension digital model and the CAD model, and the algorithm is steady and reliable.

Tomographic Imaging of P and S Wave Velocity Structures Beneath North China and its Vicinity

WANG Zhi-shuo, WANG Chun-yong, CENG Rong-sheng, WANG Xi-li

2008, 17(2): 15-27.

Abstract(3026) PDF(8)

Abstract:
The regional travel-time data from 475 seismic stations in the North China and its vicinity were used to inverse the P and S velocity structures of the crust and uppermost mantle.The pseudobending ray tracing algorithm was used to calculate the travel times.The large and sparse system of observation equations is solved by using the LSQR algorithm.According to the checker-board tests,reliable inversion results were obtained for a parameterized model with grid size of 0.5°by 0.5°in the horizontal directions and 5 nodes of 1,10,25,42 and 60 km in depth.The Yangtze Block and the Sino-Korean Block are located in two sides of the Qinling-Dabie orogenic belt.The differences of velocity structure between two Blocks are that lower velocity anomaly exists in most part of the Sino-Korean Block,while velocity distribution is normal in the Yangtze Block.This indicates that the Yangtze Block is relative stable,and the Sino-Korean Block is still active,where strong earthquakes have frequently occurred.Main features of the velocity structure in the Sino-Korean Block are that major tectonic belts (such as Yanshan uplift,Taihangshan piedmont fault belt,Tanlu fault belt,and Qinling-Dabie orogenic belt)are located in the low velocity areas or the transition zone from low velocity area to high velocity area in the crust and upper mantle.In the Tangshan earthquake area,low velocity anomaly commonly exists at the depth of 25 km,42 km and 60 km,which may imply that the hot material in upper mantle upweUs,and then stops to the lower part of upper crust.

The Abnormal Characteristics of Apparent Resistivity in Direct Current Electric Methods on Artificial Cavity

GONG Sheng-ping, LI Zhen-yu, YU Yong-peng, ZHOU Xin, HUANG Wei

2008, 17(2): 28-33.

Abstract(2211) PDF(2)

Abstract:
According to the practical geological conditions, different arrays can be chosen for detecting underground artificial cavity. The structure message of the cavity can be obtained roundly by the comprehensive contrasting of the results. In this paper, we take one subterranean artificial cavity as an example. By using different arrays, comprehensive contrasting the abnormal characteristics and results, the effectiveness of the DC methods in detecting underground artificial cavity is demonstrated.

A Low Profile Monopole Antenna for Breast Cancer Imaging

ZHAO Yan, SHI Qiao-lian

2008, 17(2): 34-39.

Abstract(2380) PDF(6)

Abstract:
In this paper, a novel wideband microstrip-fed monopole antenna with a size of only 24 mm×31.7 mm×1.6 mm is studied by the method of moment based on the two-level hi-conjugate gradient-fast Fourier transform method. The antenna has a wide bandwidth ranging from 3.1 GHz to 11 GHz for Sn₁₁〈-10dB (S₁₁ denotes the return losses). Details of the proposed antenna design approach and measured results are presented and discussed, which can be used for Ultra-wideband applications in the area of breast cancer imaging.

An Sequence Subsets Simultaneous Algebraic Reconstruction Techniques

KONG Hui-hua, PAN Jin-xiao

2008, 17(2): 40-45.

Abstract(1184) PDF(0)

Abstract:
A major drawback of the iterative image reconstruction algorithms is their high computational cost. To decrease computation time, an Ordered Subsets (OS) method was proposed by Hudson et al. Because the OS algorithm uses a fixed number of subsets for each iteration, the quality of images depends upon the number of subsets. In this paper, we develop a new algorithm called the sequence subsets SART, which decrease the number of subsets after each iteration. Thus we not only accelerate convergence of the reconstructed image but also recover various frequency components of the reconstructed image in early iterative steps. Experimental results show that the proposed sequence subsets SART can provide higher quality reconstructed images that are very insensitive to noise at a small number of iterations.

Volume Rendering of Multilayer Surface Based on Data From CBS Scanner

HAN Yu, XIA Xiao-niu, SHAO Li-kang, DING Hou-ben

2008, 17(2): 46-50.

Abstract(1212) PDF(1)

Abstract:
Based on CBS scanning data, constructs the file of CBS volume data, brings forward an improved volume data division method to achieve the fast and accurate extraction of fringe surface and optimizes algorithm.

The Clinical Value of 3 Dimensional Reconstruction for Multiplex Spiral CT in Acetabulum Fracture

QUAN Qiang, REN Zhong-qing, HU Chun-feng, XU Kai

2008, 17(2): 51-54.

Abstract(1261) PDF(0)

Abstract:
Objective: To evaluate the clinical value of 3 dimensional reconstruction for multiplex spiral computer tomography (MSCT) in acetabulum fracture. Methods: 38 patients with acetabulum fracture examined by X-ray plain film and 3 dimensional reconstruction imaging were analysed retrospectively. Results: In 38 cases with acetabulum fracture, 34 patients were diagnosed accurately, 3 patients was suspected,and 1 patient was missed by X-ray plain film, 24 patients were classificated accurately by X-ray plain film. 38 patients with acetabulum fracture were diagnosed accurately and classificated by 3 dimensional reconstruction imaging. Conclusion: 3 dimensional reconstruction for multiplex spiral CT could clearly demonstrate the acetabulum fracture location, sizeand so on. 3 dimensional reconstruction for MSCT is better than X-ray, it plays an important role in the diagnosis of acetabulum fracture and in the surgical plan designing.

CT Diagnosis and Clinical Pathological Analysis of Gastrointestinal Stromal Tumors

BI Chun-long, WAN Xia, ZHANG Wei

2008, 17(2): 55-60.

Abstract(1006) PDF(0)

Abstract:
Objective: To improve the ability of CT diagnosis of gastrointestinal stromal tumors (GIST) through analyzing imaging findings of GIST. Methods: Plain and enhanced spiral CT scan: was performed in 32 patients with GIST which were proved by operation and pathology. Results: All 32 cases originated single, 17 were located in stomach, 7 in jejunum and ileum, 3 in colon and rectum, 1 in esophagus, 2 in and 2 in duodenum and posterior peritoneum. 9 cases were benign and 23 cases were malignant in 32 cases with GIST. The imaging appearance of CT included submucous hypervascular lesions with predominating exophytic growth. There were obvious necrosis, cystic changes or calcification within the mass. The degree of enhanced CT were more marked in venous phase compared with that in arterial phase. Conclusion: CT is useful imaging technique in the diagnosis of GIST. The imaging findings of CT can reveal some characteristic signs of GIST. CT can precisely localized GIST and is helpful in differentiating benign with malignant GIST. The imaging of CT has important value in differential diagnosis, however, the qualitative diagnosis needs depend on immunohistochemical and eleetronmicroscopic examinations.

Effect of Focal Spot Size on Image Quality in 64-Row MDCT Brain Imaging

LIU Jia-bin, LI Kun-cheng, DU Xiang-ying, LI Peng-yu

2008, 17(2): 61-65.

Abstract(1394) PDF(5)

Abstract:
Objective: To evaluate the effect of different focal spot sizes on image quality in 64-row MDCT brain imaging. Method: Plain cranial axial CT scans were performed on twenty healthy volunteers with GE LightSpeed VCT (64×0.625 mm detectors, small focal spot size 0.6 mm×0.7 mm, large focal spot size 0.9 mm×0.9 mm). Informed consents were obtained in all volunteers. Axial scans across the posterior cranial fossa were performed with different focal spots on all subjects, with the other parameters not changed. The images were printed at the same window setting with Kodak Dryview 8700 laser imager and reviewed by two radiologists to rate the artifacts of bony structures at posterior cranial fossa. The results were analyzed with SPSS 11.5 for Kappa test and intragroup Chi-square test. Results: The two radiologists were in accordance with the rating of the artifacts at posterior cranial fossa (Kappa = 0.57). Less artifacts were observed at posterior cranial fossa with small focal spots than with large focal spots (P<0.05). Conclusion: Artifacts of cranial base can be reduced by using small focal spots on 64-row MDCT brain scan. Using small focal spot in clinical examination, better image quality can be achieved in brain CT scan.

A Preliminary Study of CT Perfusion Imaging and Dynamic Enhanced for Lung Nodule

DENG Jia-xiu, ZHANG Yong-dong, FENG Feng-yin, LIU Juan, CHEN Yu-ying

2008, 17(2): 66-73.

Abstract(1246) PDF(1)

Abstract:
Objective: To study the roles of CT perfusion imaging and dynamic enhanced for diagnosis of lung nodule. Methods: The dynamic contrast-enhanced CT were performed with single-slice spiral CT in 34 patients with lung nodule (including: 17 cases of malignant nodule, 11 cases of benign nodule, and 6 cases of active inflammatory nodule). The CT perfusion imaging and dynamic enhanced CT were performed with two-slice spiral CT in 45 patients with lung nodule (including: 24 cases of malignant nodule, 13 cases of benign nodule, and 8 cases of active inflammatory nodule). According to dynamic contrast-enhanced examination, CT values of the nodules at different delay time were got to describe the time-density curve in all cases. The perfusion parameters, including Blood Flow, Blood Volume, Mean Transmit Time and Permeability Surface, were acquired with body perfusion-2 software, and they were analyzed and compared among three groups of lung nodules. Results: The time-density curve of the benign pulmonary nodules was fiat with enhancement only about 10 Hu. The malignant nodule increased rapidly at early time and maintained a plateau with decreased slowly in delay phase, with enhancement of CT value about 46 Hu. Whereas the active inflammatory nodule increased rapidly and come down also rapidly, with enhancement of CT value about 62 Hu. The values of blood volume and permeability surface in malignant and active inflammatory nodule are greater than that in benign pulmonary nodules. The values of blood volume and permeability surface in benign nodules are less than 6.5 mL/100g and 30 mL/100g min, respectively. Conclusion: CT perfusion imaging can provide quantitative information of blood perfusion within lung nodules, CT perfusion imaging and dynamic enhanced CT is helpful for differentiating lung nodules.

CT Findings of Med-Diffuse Large B-Cell Lymphoma

LI Xiao-yang, LI Hui-ju, ZHONG Hong-bo, HU Wen-jian

2008, 17(2): 74-79.

Abstract(1470) PDF(0)

Abstract:
Objective: To investigate the CT findings of Med-diffuse large B-cell lymphoma so as to promote the diagnosistic accuracy (Med-Dlbcl). Materials and Methods: female 7 cases, male 4cases. The age is in 23-42. CT findings of 11 cases with Med-Dlbcl were retrospectively assessed. Results: 11 Med-Dlbcl case, the misdiagnosis of CT is 9 of the thymus gland lump, only 2 example in consideration of the Med-Dlbcl. Conclusion: Rise year by year in China along with the outbreak rate that the Med-Dlbcl, the doctor of CT should promote the understanding that examines a patient to that disease.

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2008 Vol. 17, No. 2