CT理论与应用研究

Using IMAGE Data for Observe the Plasma Density Distribution of the Geomagnetic Equatorial Plane

ZENG Bo, LI Liang, CHEN Zhi-qiang

2017, 26(1): 1-8. doi: 10.15953/j.1004-4140.2017.26.01.01

Abstract(659) PDF(3)

Abstract:
The IMAGE satellite has been observed the Earth’s plasmasphere for 5 years, it provides a large quantity of practicable data for the plasmaspheric research. However, IMAGE data had the three problems: ‘the earth shelter’, ‘the sunlight shadow’ and ‘the lack of data’, so the traditional CT methods can not directly reconstruct the earth’s plasmasphere. In this paper, by using the earth's magnetic field model and starting from the physical properties of the Earth’s plasmasphere, we establish a new EUV imaging model which associates with the surface density of the Earth's magnetic equator and the projection data. Then we use an ART-type technique to inverse compute this model and acquire the density distribution of geomagnetic equatorial plane. This method realized a 3D plasmaspheric density distribution was computed from the single angle of the EUV observed images. In addition, we evaluated the result by using the simulated data and the IMAGE data; it was show that the method is feasible and effective.

One-step qP-waves forward Modeling in TTI Media with Lowrank Approximation

ZHU Hao-ran, SUN Xiao-dong, LI Zhen-chun

2017, 26(1): 9-18. doi: 10.15953/j.1004-4140.2017.26.01.02

Abstract(591) PDF(5)

Abstract:
Forward modeling of quasi-P-waves (qP) in TI medium for practical application draw great attention in recent year. Lowrank two-step wave field extrapolation can eliminate the SV-wave artifacts interference, but the two-step method relies on a real-valued phase function and cannot use in large time step. For this reason, we propose qP wave one-step wave field extrapolation method based on Lowrank approximation, One-step method has the ability to handle complex-valued phase functions, we add velocity gradient term to the phase function, and successfully applied in TTI media qP wave forward modeling. By experiment shows: One-step wave field extrapolation has the advantage the traditional two-step process, no SV-wave artifacts. One-step method is more stable in the large time step, and can reduce computing costs. In the case of anisotropic, the one-step wave field extrapolation applies to any inclinations, and the result of wave field simulation is clear and accurate, with no instability.

The Study on Monochromatic Image Feature for Renal Solid Mass with Dual-energy CT in Nephrographic Phase

LEI Ping-gui, WANG Xiao-ying, WANG He, LIU Jian-xin, JIANG Jian

2017, 26(1): 19-26. doi: 10.15953/j.1004-4140.2017.26.01.03

Abstract(577) PDF(4)

Abstract:
Objective: To evaluate reconstruction parameters of monochromatic image with dual-energy CT in nephrographic phase, and find the optimal monochromatic image for displaying renal solid mass. Methods: Clinical material and imaging data of 20 patients underwent dual-energy CT examination (80 kVp/Sn140 kVp) were analyzed in this study. Various monochromatic image (40 ~ 120 keV) of Dual-energy CT were generated by 80kVp image and Sn140 kVp image. The image quality was evaluated by subjective and objective assessment. The optimal CNR and SNR monochromatic images were calculated by objective assessment for comparison with linear blending image with weighted factor 0.5. Subjective image quality evaluated by using five points grading scale method for blending linear image with weight factor 0.5 and optimal monochromatic image by two experienced radiologists. Results: Twenty patients (male 13, female 7) were enrolled in this study, mean value of CTDI_vol was (11.54 ±4.09) mGy, SSDE was (14.86 ±3.97). Objective assessment: the highest CNR and SNR of monochromatic image was 60 keV and 70 keV, respectively. Significant statistical difference was existed comparison with blending linear image with weight factor 0.5, respectively (all P<0.05). Subjective assessment: There was no significant statistical difference in the whole image quality and detail of renal lesion comparison with blending linear image with weight factor 0.5 (all P>0.05). Conclusions: Monochromatic images of 60 keV and 70 keV could get highest CNR and SNR for detection of renal solid mass, respectively, which were superior to linear blending images (M= 0.5). However, Monochromatic images of 60 keV and 70 keV were equivalent to display the whole image quality and detail of renal solid mass.

Traveltime Tomography in Imaging Domain and Application Based on Raytracing

ZHANG Zi-liang, LI Zhen-chun, ZHANG Kai, HU Bo-kai, ZHU Bai-hang

2017, 26(1): 27-34. doi: 10.15953/j.1004-4140.2017.26.01.04

Abstract(577) PDF(6)

Abstract:
Tomography is a common means of modern seismic exploration and development process, according to the traditional view of traveltime tomography inversion with the coverage problem, using the regularization constraint to solve the judgment accuracy, judging the experimental model by using pick fitting angle gather, at the same time, no longer use the original shot records to pick up the residual move out, improving the accuracy of picking travel time residuals by using linear of depth the residuals and travel time residuals. With three layers in the model and real data inversion results show that: the method can update the migration velocity field better, get the migration results more accurate, and describe the construction of small scale geologic.

Acoustic Velocity Study of Low Porosity and Low Permeability Reservoir Based on Gas Inclusion Model

BAI Bo, ZHAO Ru-min, SHI Bin-quan, CAO Xiang-yang

2017, 26(1): 35-44. doi: 10.15953/j.1004-4140.2017.26.01.05

Abstract(531) PDF(4)

Abstract:
According to the evaluation difficulty of middle-deep gas reservoir with low porosity and low permeability, the study of rock physics using modified White gas inclusion model is carried out in this paper. Firstly, the gas inclusion model is analyzed to get the calculation formula of P-wave and S-wave velocity. Then, the parameters of acoustic velocity, porosity, saturation, pressure and temperature are theoretically calculated. Finally, the calculated results are verified by laboratory experiments. This study indicated that P-wave velocity changed obviously with the water saturation variation, and S-wave velocity changed slightly with the water saturation variation. Compaction makes the P-wave velocity increases rapidly and the S-wave velocity increases slowly, which is caused by the changes of elastic modulus and shear modulus. Effect of temperature on the acoustic velocity can be neglected. The study of this paper can provide technical support for the acoustic wave velocity measurement and interpretation of complex reservoir with low porosity and low permeability.

The Application of Improved AVAZ Method in Predicting the Fractured Reservoir

SHU Meng-cheng

2017, 26(1): 45-52. doi: 10.15953/j.1004-4140.2017.26.01.06

Abstract(460) PDF(5)

Abstract:
Nowadays, it is effective to predict the fracture attributions via AVAZ technique based on pre-stack azimuthal data. However, in the seismic acquisition of narrow azimuth, the number of folds can hardly be consistent at different azimuth directions, so that different azimuth data has different energy resulting in the trend error in the prediction of fracture attributions. In this paper, the AVAZ method based on the amplitude normalization in the fractured reservoir is proposed. By adding the method into the fracture analysis step the trend error caused by the seismic acquisition could be avoided. Finally, the application results from real data shows that this method is effective and practical and it significantly improves the fracture predicted results.

The Method of Inversion Imaging Based on Matrix Pretreatment and BPT-SIRT Nonlinear Weighted

YUAN Ye, HUANG Xiao-han, WANG Zhong-gang, ZHANG Yu, JIANG Zheng

2017, 26(1): 53-62. doi: 10.15953/j.1004-4140.2017.26.01.07

Abstract(612) PDF(4)

Abstract:
In order to improve the quality of the inversion in the elastic wave CT, at the same time, taking into account the pathological characteristics of the coefficient matrix and low quality of the reconstruction image obtained by the BPT-SIRT algorithm, a method based on principal component weighting preprocessing and weighted BPT-SIRT algorithm is proposed. The initial iterative value obtained by the method of BPT is weighted, then, adding a weight to the principal component of the coefficient matrix, the element of ray matrix is weighted by the nonlinear exponential weighting function. The method is verified by numerical simulation and concrete filled steel tube specimens with defects. The results show that the method has better convergence speed and accuracy, and the recognition effect is better.

Application and Research on Reconstructed Wavelet Threshold Functionin Signal Denoising

CHEN Jian-yong, WANG Dao-kuo, DENG Wen-feng, YUAN Pei-xin

2017, 26(1): 63-68. doi: 10.15953/j.1004-4140.2017.26.01.08

Abstract(543) PDF(8)

Abstract:
In practical engineering applications, the signals collected by physical methods have noise information and this will submerge many useful signals used for analyzing the system characteristics. The traditional filtering techniques, such as band pass, low pass, high pass, seems powerless, so extracting useful feature information requires denoising of the original signal. Common wavelet threshold denoising methods have many shortcomings. In this paper, a threshold function is re-constructed on the basis of wavelet threshold denoising methods. To realize the simulation of denoising the Gaussian white noise, in the Mtalab (2014a) environment, the conventional hard, soft threshold function and the new threshold function are respectively used. Results show that signals become better and clearer by using the new threshold function.

Diagnostic Value of the Vascular Convergence Sign of Solitary Pulmonary Nudules on 3D Reconstruction

CHEN Zi-min, XIANG Zi-yun, WANG Yi, ZHAN Yong, YU Hui

2017, 26(1): 69-76. doi: 10.15953/j.1004-4140.2017.26.01.09

Abstract(667) PDF(6)

Abstract:
Objective To explore the diagnostic value of the vascular convergence sign of solitary pulmonary nodule (SPN) on 3D reconstrucion. Materials and Methods Helical CT scans of 63 patients with SPN confirmed by pathology were reviewed and and analyzed.3D reconstruction was made using MPR and VR. Manifestation of the vascular convergence sign of the tumor was observed. A difference in the result was found between MPR and VR, benign and malignant SPN. Results: The rate of visualization of the vascular convergence sign of SPN in VR was higher than the one in MPR (P<0.05). The rate of visualization of the vascular convergence sign in benign SPN was higher than the one in malignant (P<0.05). Conclusion: 3D reconstrucion can demonstrate vascular convergence sign effectively. VR is an effective method for the differentiation of benign SPN with malignant lesions.

The Diagnositic Value of MSCT on Bowel Ischemia

WANG Bao-hai, SUN Jing-tao, LI Qian, WANG Lai-you, WANG Dong-ping, LIU Xiao-jun, ZHOU Xiao-sen

2017, 26(1): 77-84. doi: 10.15953/j.1004-4140.2017.26.01.10

Abstract(492) PDF(7)

Abstract:
Objective: To explore the finding and diagnostic value of MSCT in intestinal ischemia disease and provide help for clinical treatment. Methods: Retrospective analysis the MSCT plain and enhanced performance of intestinal ischemic lesions in 55 cases were final diagnosed by DSA, surgery, pathology or clinical. Results: Of the 55 patients, there were superior mesenteric artery embolism or thrombosis in 13 cases, mesenteric venous thrombosis in22 cases, ischemic colitis in 2 cases, volvulus in 6 cases, intestinal obstruction in 5 cases, intussusceptions in 4 cases, internal abdominal hernias in 3 cases. The MSCT and CTA findings of the 55 patients, there were lumen expansion and effusion in41 cases, mesenteric edema in 33 cases (cable levy in 5 cases, fat muddy levy in 27 cases, product gas in 1case), mesenteric vascular abnormalities take shape in 17 cases (there were whirlpool sign in 5 cases, abnormal position in 10 cases), vascular stenosis or filling defect in35 cases. Conclusion: MSCT findings of intestinal ischemia lesions has high sensitivity and certain characteristic, it should be as routine and preferred examination, at the same time refer to clinical manifestations, we can make the correct diagnosis and provide the basis for accurate clinical treatment for the important action of the etiologies and differential diagnosis.

Application of Diffusion Tensor Imaging in the Early Diagnosis of Parkinson's Disease

YANG Tao, ZHANG Chun-yan, CHENG Jing-liang, LIU Kang-yong, FAN Xiao-jun, WANG Wei, ZHANG Ye, LIU Fei

2017, 26(1): 85-90. doi: 10.15953/j.1004-4140.2017.26.01.11

Abstract(505) PDF(5)

Abstract:
Objective: To explore the diagnostic value of diffusion tensor imaging in early Parkinson disease (PD). Methods: There were 18 patients with primary early PD and 18 volunteers as control group. Conventional MR sequences and DTI images were examined. The fractional anisotropy (FA) value and apparent diffusion coefficient (ADC) value of the bilateral thalamus, caudate nucleus, substantia nigra, putamen and globus pallidus were evaluated. Results: The FA value of thalamus, caudate nucleus and substantia nigra in PD group was significantly lower than that in the control group (P<0.05). The FA value of bilateral putamen and globus pallidus was no significant difference between the two groups (P>0.05). No significant difference was found in ADC value between the two groups. Conclusion: The changes of FA value in the thalamus, caudate nucleus and substantia nigra can help to recognize and detect PD. This study suggests that DTI may provide valuable clue for early diagnosis of PD.

Analysis of MDCT Features on Pulmonary Small Cell Neuroendocrine Tumor

JA Ya-jun, YANG Zhi, YANG Da-xing, FU Bing, LI Chun-ping, CHEN Tian-wu, YANG Fan, LI Rui

2017, 26(1): 91-98. doi: 10.15953/j.1004-4140.2017.26.01.12

Abstract(476) PDF(4)

Abstract:
Objective: To explore CT features of pulmonary small cell neuroendocrine tumor. Methods: Imaging findings of 28 patients with pathologically confirmed pulmonary small cell neuroendocrine tumor were retrospectively analyzed, all patients underwent plain CT and contrast enhanced CT examinations. Results: There were 18 cases were central type. Mass or nodule in hilar or medisatina side and thick Bronchial wall were seen in 18 (88%). Hilar and mediastinal lymphadenopathy were seen in 15 (83%). Mass and lymph nodes were significantly heterogeneous enhancement with contrast enhanced CT examination. 10 cases fell into peripheral carcinoma without features of CT. Conclusion: Pulmonary small cell neuroendocrine tumor is mainly as bronchial wall thickening with mass, the tumor has homogeneous density with hilar and mediastinal lymph nodes.

Feasibility of 80 kVp Ultra-low Dose Scan Protocol in Prospective Coronary CT Angiography

TIAN Zhi-nan, LONG Shi-liang, ZHAO Yue, TAN Hong-wen

2017, 26(1): 99-106. doi: 10.15953/j.1004-4140.2017.26.01.13

Abstract(488) PDF(5)

Abstract:
Objective: To investigate the feasibility of prospective coronary computed tomography angiography (CTA) using tube voltage of 80 kVp in patients with low body mass index (BMI). Methods: Eighty-four patients with suspected coronary artery disease (CAD) underwent prospective ECG-gate coronary CTA. The cases were divided into two groups based on BMI: One group (BMI ≤ 22kg/m²) was examined with 80 kVp, and the other group (22< BMI ≤25) with 100 kVp. If heart rates < 65beats/min, pulse exposure time was set at 200 ms, otherwise 380ms. The imaging qualities of coronary artery segments with diameter ≥1.5 mm were evaluated. Image quality and radiation dose were compared between groups. Results: The age, height, and heart rate were insignificantly different between groups. In the 80 kVp and 100 kV groups, the EDs were 0.56 ±0.21 and (1.43 ±0.58) mSv, respectively. There were significant differences in CT dose index volume (CTDIvol), dose length product (DLP) and ED between groups. The image quality rates (score of 3 or 4) were 92.2% and 91.8% in the 80 kVp and 100 kVp groups, respectively. In image quality scores, aortic SNR and coronary trunk CNR had no significant differences between two groups. Conclusion: Prospective coronary CTA using tube voltage of 80 kVp in low-BMI patients can provide adequate coronary diagnostic information; while significantly reduce the radiation dose.

Multi-slice Spiral CT Virtual Endoscopy in Diagnosis of Adult Bicuspid Aortic Valve Deformity

LI Jing, LIU Huai-jun, GUO Qing-le, LIU Jing-wang, WANG Jun-qi

2017, 26(1): 107-114. doi: 10.15953/j.1004-4140.2017.26.01.14

Abstract(552) PDF(7)

Abstract:
Objective: To investigate the clinical value of MSCT virtual endoscopy (CTVE) in diagnosis of adult bicuspid aortic valve deformity. Methods: From March 2010 to August 2015, eight cases with calcification of aortic valve underwent 128-slice spiral CT coronary angiography (CTCA) examination were presented bicuspid aortic valve deformity intuitively under CTVE. The thickness of aortic valve and the maximum diameter of the ascending aorta were measured. Results: Eight cases with calcification of aortic valve were presented bicuspid aortic valve deformity intuitively under CTVE, through the CTCA, other merger cardiovascular malformations can be found, and included 6 cases of aortic widened, one case of abnormal left coronary artery origin. And thickened aortic valve was found in 5, no thickening of the aortic valve in 3.Conclusion: Application of CTVE in CTCA examination visualize the structure of the aortic valve, and can find other vascular malformation, observe coronary artery, so as to rule out other diseases. Moreover, CTVE and color Doppler echocardiography can complement each other

The Manifestation of CT Colonography on Detecting Transperitoneal Invasion about Gastric Cancer

JIN Zhao, BAO Li-wei

2017, 26(1): 115-120. doi: 10.15953/j.1004-4140.2017.26.01.15

Abstract(500) PDF(4)

Abstract:
Objective: To evaluate the diagnostic value of CT colonography (CTC) in detection of transperitoneal invasion from gastric cancer. Method: Eight gastric carcinoma patients underwent CTC for preoperative work-up. Although no obvious peritoneal nodule was seen on axial CT images, colonic wall deformities were noted on three-dimensional (3D) air images. Multiple Planar Reconstruction (MPR) images revealed thickening colonic wall at the deformities, and in addition, we also observed dense cordlike structures which connecting the primary gastric cancer and colonic wall thickening. Results: on one hand, cordlike indurations consistent with peritoneal invasion were found to connect the primary gastric cancer, gastrocolic ligament, and transverse mesocolon during exploratory surgery. On the other hand, we observed colonic scars consistent with peritoneal invasion. Conclusion: All of observations suggest that CTC could be use for the differentiation of gastric cancer and transperitoneal colonic invasion.

Research Progress in Risk Assessment of Ruptured Intracranial Aneurysms

SHI Shi-kui

2017, 26(1): 121-128. doi: 10.15953/j.1004-4140.2017.26.01.16

Abstract(477) PDF(4)

Abstract:
Rupture of intracranial aneurysms can lead to fatal subarachnoid hemorrhage, its pathogenesis and the mechanism of rupture has not been fully clarified. Some aneurysms will not rupture in lifetime, no obvious clinical symptoms or only mild clinical symptoms, which need not be special treatment; some aneurysms can rupture in young ages, even life-threatening. Therefore, it is of great clinical significance to assess the risk factors and the inducing factors of intracranial aneurysms rupture.

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2017 Vol. 26, No. 1