CT理论与应用研究

Numerical Simulation of Excitation Source with Medium of Different P-wave Velocity

YU Lu-yang, TIAN Gang, WANG Yi-min

2016, 25(3): 251-260. doi: 10.15953/j.1004-4140.2016.25.03.01

Abstract(567)

Abstract:
Source excitation is an important factor of the effects of seismic exploration. Choosing the appropriate excitation parameters in oil and gas exploration in order to get better seismic record is necessary. By using the software ANSYS/LS-DYNA, we adopted Lagrange algorithm based on the finite element method to simulate the seismic source of the cylindrical explosive. In this paper we focus on the frequency component of excited seismic waves in single well. Through the study of explosive detonation velocity and explosive shape we conclude that the dynamite with low detonation velocity and elongated grains has high excitation frequency and energy in the medium with low P-wave velocity, but the dynamite with high detonation velocity and short-thick shape has high excitation frequency and energy in the medium with high P-wave velocity. We want to provide references for the choices of excitation parameters in actual exploration to save exploration costs.

Fresnel Zone Travel-time Tomography Based on Multi-band Frequencies' Combination

TIAN Ya-jing, YANG Guo-quan, ZHANG Min, LI Zhen-chun, WANG Zheng

2016, 25(3): 261-268. doi: 10.15953/j.1004-4140.2016.25.03.02

Abstract(492)

Abstract:
To resolve the problems of tomography based on ray theory, Fresnel tomography discards the concept of zero-width geometric ray. Taking into account the seismic signal has a certain bandwidth, high-frequency radiation path not only on the nature of the medium will affect the propagation of seismic waves, rays near the same media features will affect the propagation of seismic waves. We propose the Fresnel zone travel-time tomography based on multi-band frequencies' combination. This paper starts from the Born and Rytov approximation of frequency-domain wave equation to derive the travel-time sensitivity kernels of wave equation on the band-limited wave-field and the travel-time residual can be obtained based on the Rytov approximation at the same time. Meanwhile, we enhance the resolution and precision by combining multiple frequencies during different stages of iteration. The inverted result proves that our method has a higher resolution and accuracy

Study on the Value of Dual Source CT Assessment of Correlation between Hypertension and Coronary Plaque

YANG Yang, SHEN Bi-xian, CHEN Sheng-ji, HUANG An-rong

2016, 25(3): 269-277. doi: 10.15953/j.1004-4140.2016.25.03.03

Abstract(563)

Abstract:
Objective: To investigate the correlation between hypertension and the formation of coronary atherosclerotic plaque by DSCTA. Methods: Collect patients who underwent coronary DSCTA from April 2014 to August 2015 and divided into hypertension group(n= 150) and non-hypertension group(n= 150) on the basis of cases. The hypertension group was divided into high pulse pressure(PP > 60 mm Hg) and low pulse pressure(PP < 60 mm Hg) group. The incidence rate of plaque, distribution characteristics and types were observed. Results: The incidence rate of 3 and above coronary artery vascular lesions was 61.7% in hypertension group and 45.3% in non hypertension group. The incidence rate of plaque was 28% in hypertension group and 19.2% in non hypertension group, the difference between the two groups were statistically significant(P < 0.05). The degrees of coronary artery stenosis between hypertension and non hypertension groups have no significant differences, but Severe stenosis was 8.6% and occlusion was 3.7% in high pulse pressure group; and were 4.4% and 0.8% respectively in low pulse pressure group, the difference were statistically significant(P < 0.05). Occurrence rate of mixed plaque was 54.5% in hypertension group and 43.0% in non hypertension group. The incidence of non calcified plaque was 40.6% in hypertension group, 50.7% in non hypertension group, the difference were statistically significant(P < 0.05). Occurrence rate of mixed plaque was 57.5% in group 1 and 49.1% in group 2,the difference between the two groups were statistically significant(P < 0.05). Conclusion: DSCTCA can evaluate the relationship between the hypertension and coronary artery plaque. The range of coronary involved by plaque is wider, incidence rate of mixed plaque is higher and having more risk prone to cardiovascular events in hypertension, and will be more serious with higher pulse pressure.

The Study of the Image Quality of Dual Energy Spectral CT in the Assessment of Myocardial Infarction

BU Yu-lian, ZHANG Huan, PAN Zi-lai, YANG Wen-jie, CHEN Ke-min, YAN Fu-hua

2016, 25(3): 279-286. doi: 10.15953/j.1004-4140.2016.25.03.04

Abstract(506)

Abstract:
Objective: To study the effectiveness of the functional parameters of spectral CT, and to explore their clinic values of image quality in the evaluation of myocardial infarction(MI), so as to provide a novel and reliable imaging diagnostic system for early detection of MI. Methods: 30 patients with coronary heart disease were scanned with the conventional coronary CT angiography(CCTA) and the dual energy spectral imaging modes. In addition, all cases had the Cardiac MRI scan within a week. CCTA images were used to measure stenoses. The optimal contrast-to-noise ratio(CNR) and the optimal monochromatic energy levels for displaying infractions were measured from 1 min and 3 min monochromatic images. Record the image noise according to the optimal monochromatic energy levels. The results were compared with those measured from conventional 140 k Vp polychromatic images. Detect MI in MRI perfusion images and compare with those detected by CT. Results: Spectral CT have detected 36 regions of MI and had good correlation with the myocardial perfusion images of MRI(r = 100%, P = 0.00). All spectral CT-identified MI had associated coronary artery with more than 50% stenosis of the intravascular diameter(71.7% ± 16.2%). The optimal CNR for displaying infractions of 1 min and 3 min monochromatic images were significant higher than the CNR of conventional 140 k Vp polychromatic images(P < 0.05). The image noise according to the optimal monochromatic energy levels of 1 min and 3 min monochromatic images were significant lower than conventional 140 k Vp polychromatic images(P < 0.05). Conclusions: The GSI mode of dual energy spectral CT greatly improves the image quality and the efficiency of the detection of MI.

Application of Regularization Method in Radio Wave Tomography

DONG Yi-fei, ZHANG Zhi-fu

2016, 25(3): 287-298. doi: 10.15953/j.1004-4140.2016.25.03.05

Abstract(581)

Abstract:
Radio-wave penetration method is one of the most popular methods for geological detection. Based on Simultaneous Algebraic Reconstruction Technique(SIRT) method, the attenuation coefficients of coal seam are reconstructed. But the inversion resolution for SIRT tomography method is reduced by the poor geometry and low SNR data acquired in mine tunnel. In our study, the Tikhonov and Total Variation(TV) regularization methods for minimization problem are derived to inverse the attenuation coefficients and the influence factors of inversion results are discussed to account for effect on model solutions.Conclusionsare reached from inversion experiment for theoretical models and field data. Regularization methods have better inversion resolution than SIRT method. More fold and higher SNR are important factors to obtain high resolution result. For Tikhonov regularization method, increasing regularization parameter makes the inversion result smoother, while decreasing parameter causes the result closer to the geological anomalies. TV regularization method has opposite property. The inversion result for field data well conform to the known geological anomalies, which shows the feasibility and reliability of the two regularization methods for practical application.

Prediction of the Sweet Spots within Shale Gas Reservoirs by Using Nonlinear Inversion of Seismic Data Acquired from Baojing Area Hunan Province

LIANG Guo-hua, HUANG Han-dong, LIU Fu-yi, FU Chao, LIN Zhong-yue, WANG Xiang-hao, YANG Ya-di, MIAO Yu-xin, SHEN Jin-song, ZHANG Xiao-chen

2016, 25(3): 299-310. doi: 10.15953/j.1004-4140.2016.25.03.06

Abstract(497)

Abstract:
Facing the difficulties of various near surface formations in Baojing area, Hunan province, and significant tilt of the subsurface formation and structure, and hence caused low signal/noise ration of the seismic data, and the low contrast of seismic impedance between the shale gas reservoir and the shoulder shale, we have investigated integrated evaluation method that consists of four steps of sensitive well logs reconstruction and optimal processing, nonlinear inversion of seismic data constrained with sedimentary facies, and fluid detection by using poststack seismic data. Comparison of the seismic inversion results and fluid detection results of several inlines with that of the borehole shows sound consistency, and verified the effectiveness and practical usefulness of our method.

The Application of Seismic Wave CT to Qualities Detection of Concrete Cut-off Walls

PAN Ji-shun, SONG Chao-yang, LENG Yuan-bao, LI Yan-zhuo, WANG Xin-jian, ZHAO Xiang, GAO Dong-pan, LI Di

2016, 25(3): 311-317. doi: 10.15953/j.1004-4140.2016.25.03.07

Abstract(501)

Abstract:
Plastic concrete cut-off wallsare underground concealed work, playing a decisive role in seepage control, and the quality of cut-off walls directly affects the anti-seepage effect. The seismic wave CT may be an effective way to detect the quality of cut-off walls. We applied the seismic wave CT technology to detect concrete cut-off walls. We also compared the seismic CT results with the borehole core, geotechnical test and water injection test. All show that the seismic wave CT is a fast, accurate and reliable method to detect the quality of concrete cut-off walls. Seismic wave CT has a broad prospect in the nondestructive quality testing of concrete cut-off walls.

Effectiveness Analysis of Forward Modeling and Ghost Suppression for Two Kinds of Variable-depth Streamer Acquisitions

ZHOU Han-rui, SONG Jian-guo, GONG Yun-liang

2016, 25(3): 319-330. doi: 10.15953/j.1004-4140.2016.25.03.08

Abstract(479)

Abstract:
In recent years, variable-depth streamer acquisition is a kind of seismic exploration technique. The mainly propose of this acquisition is to suppress ghost and obtain high quality broadband seismic data. The commonly used variable-depth streamers are linear streamer and curved streamer, which could obtain more high frequency and low frequency information. By comparing the different parameters of seismic data and de-ghosting data, we found that curved variable-depth streamer data in wave-field analyze showed better characteristics, and have a higher signal-to-noise ratio. That is to say, the observation system of curved variable-depth streamer is superior to the linear variable-depth streamer. According to the result, it is recommended that curved variable-depth streamer is a better choice in the seismic exploration.

Application of the Strong Shielding Peeling Technique Based on Matching Pursuit Algorithm in the Reservoir Prediction of Fan 159 Well Block

LIU Lei, ZHANG Qiu, ZHANG Jun-hua, BAN Li, LI Jun-lin

2016, 25(3): 331-337. doi: 10.15953/j.1004-4140.2016.25.03.09

Abstract(548)

Abstract:
When the cap rock above the reservoir containing thick source rocks and other special strata, the reflection of the overlying strata will show strong amplitude, it will hide the reservoir information and make it present as a weak reflection, thereby interference normal description and prediction of reservoir. Therefore, eliminating the effect of interference layer on seismic reflection of reservoir, enhancing weak reflection signal is very important to improve the accuracy of reservoir prediction and determine the distribution of reservoir space. Fan 159 well block is located in the Midwest Fandong area. In this area, it containing high resistance and high speed thick hydrocarbon source rocks above the reservoir, it has a strong effect on the underlying reservoir, and it must be stripped. In this paper, we use F159 area as an example, analyses the geophysical characteristics of reservoir, study the matching pursuit algorithm based on horizon control, and finally peel off the strong shielding layer. We compared the section attributes and horizon attributes, it can be found that the recognition accuracy of reservoir is obviously improved.

Application Value of the Research Dual-energy CT Color Coding Technique to Patients with Gout Deposition of Monosodium Urate

LIU Li, JIN Mei, SHEN Jian, LIN Yi-jun, GAO Zhen-xing, WANG Kai-le, CHEN Tong

2016, 25(3): 339-348. doi: 10.15953/j.1004-4140.2016.25.03.10

Abstract(593)

Abstract:
Objective: To evaluate dual source CT dual energy(DECT) color coding technology in patients with gout urate crystals and different clinical period the relationship, between blood uric acid and further evaluation of dual-energy CT imaging in the gout screening application value. Methods: Retrospective analysis 120 cases of patients with Hyperuricemia or gout dual-energy CT imaging characteristics and clinical data, According to the clinical stage can be divided into two groups of 92 cases of male and female 28 cases; 30 cases of control group for the pseudogout patients, male 26 cases, female 4 cases, All cases of hand, footline DECT non enhanced scan, thin layer after restructuring would transmit the original data to choose MMWP workstation Dual Energy GOUT software, image post-processing, comparing the difference between the patients with GOUT two uric acid salt deposition and uric acid value relevance, and DECT detection urate deposition area and the difference of clinical evaluation. Using t test and chi-square test, Fisher exact probability statistical analysis. Results: Three groups of gender and age, there was no statistically significant difference(P_age= 0.236, P_gender= 0.613, P > 0.005). Urate deposition quantity high uric acid group was obviously higher than that of uric acid in the normal group, two groups have significant statistical significance(P = 0.00013, P < 0.001); Gout group detection rate compared with the control group, with significant difference statistically significant(P = 0.00015, P < 0.001). Conclusion: DECT imaging of urate crystals, the deposition has a good ability of hyperuricemia, early gout patients and suspected gout have a higher detection rate, can be used as a routine examination gout screening project, has high clinical value.

Correlation between MSCTE Evaluation of Crohn's Disease Activity Index and the Harvey-Bradshaw Index

YE Wen-wei, ZHANG Yan-hong, LI Zhong-rong, GUO Tian-chang, CHENG Wei-guang, CHEN Yi-bin, LIU Qin

2016, 25(3): 349-354. doi: 10.15953/j.1004-4140.2016.25.03.11

Abstract(962)

Abstract:
Objective: To investigate Multi-slice Computer Tomography Enterography(MSCTE) evaluate Crohn's disease activity index(CDII) and the Harvey-Bradshaw Index(HBI) correlation. Method: Select from July 2014 to March 2016 two hospitals confirmed by pathology CD 30 patients for the study, after HBI score, MSCTE scan, score table to evaluate Crohn's disease activity index based on CD image index, comparison CDII and HBI difference CD activity classification and correlation. Conclusion: CDII and HBI difference in the classification of each CD was not statistically significant(P > 0.05). Spearman correlation analysis CDII and HBI in CD activity at all levels were significantly correlated. Result: CDII and HBI was significantly correlated with a higher clinical value.

CT and MRI for Diagnosing of Multiple Hepatic Biliary Hamartoma in Adult

HU Li, WU De-hong, YU Gang, CHEN Ping-you, CHEN Xue-qiang

2016, 25(3): 355-362. doi: 10.15953/j.1004-4140.2016.25.03.12

Abstract(498)

Abstract:
Objective: To analyze the CT and MRI features of multiple hepatic biliary hamartoma in adult to improve diagnostic level. Methods: Retrospectively analyzed the clinical and imaging features of 12 patients with pathologically confirmed multiple hepatic biliary hamartomas and summarized the imaging features. Results: Plain CT scan showed multiple lesions which were low density, diffuse or scattered in the distribution, unclear boundary, varied shapes, the diameter of the most of lesion was less than 15 mm, no enhancement in contrast enhanced scan. The signal of lesions was lower than that of normal liver parenchyma in the T₁ WI sequence, markedly hyperintensity in T₂ WI sequence which showed clearer. The T₂ WI sequence was better than CT and T₁ WI in finding quantity of the diseases. Most of lesions with no enhancement, a few foci showed nodular enhancement or slightly circular enhancement. MRCP showed intrahepatic multiple type cystic lesion with high signal and with the bile duct is not connected. Conclusion: CT and MRI findings of multiple hepatic biliary hamartoma in adult had a certain characteristic, but still need to be identified with Caroli disease, liver cystic metastases, multiple liver cysts, polycystic liver and other liver cystic lesions.

The Variations on Bilateral Renal Artery: A Primary Study with CE-MRA

XU Jing-ci, CHEN Ke-min, PAN Zi-lai, RAO Min, LIU Xiao, SU Wen-ting

2016, 25(3): 363-368. doi: 10.15953/j.1004-4140.2016.25.03.13

Abstract(540)

Abstract:
Objective: To evaluate the category of the variations on bilateral renal artery and clinical significance with Contrast enhancement MR angiography(CE-MRA). Methods: CE-MRA of 213 patients were retrospectively analyzed. The variations on bilateral renal artery were observed and classified. Results: According to the number of the main renal artery, the anatomy of renal artery was classified in details. The incidence of early branch of the main renal artery and accessory renal artery was 6.57%(28/426) and 13.15%(56/426), respectively. Significant difference of variation incidence was found between male and female. No statistical difference of variation incidence was found between left and right kidney. Conclusion: Anatomical variations on renal artery can be showed clearly with CE-MRA.

CT and MR Manifest Features of Posterior Shoulder Instability

DAI Shi-peng, PANG Jun, DAI Jing-ru

2016, 25(3): 369-375. doi: 10.15953/j.1004-4140.2016.25.03.14

Abstract(554)

Abstract:
Objective: To evaluate the manifestations of Posterior shoulder Instability on CT, MRI. Methods: 16 cases of Posterior shoulder Instability were examined both by CT, MRI and arthroscopy and to analyze the manifestations on CT, MRI. Results: Posterior shoulder Instability included Glenoid hypoplasial, Reverse osseous Bankart fracture, Reverse Hill-Sachs fracture, Bennett lesion, Lesions of the posterior labrum and capsular complex, posterior subluxation or dislocation of the humeral head relative to the glenoid fossa. Conclusion: Lesions of the glenoid and humerus, posterior glenoid labrum, and posterior joint capsule can be identified on CT, MRI in patients with posterior shoulder instability. CT, MRI is a good examine method of Posterior shoulder Instability.

MSCT Diagnosis of Sigmoid Volvulus

HU Li, YANG Tao, YU Gang, HUANG Yan-yan, GU Jing-hua

2016, 25(3): 377-384. doi: 10.15953/j.1004-4140.2016.25.03.15

Abstract(472)

Abstract:
Objective: To discuss the imaging characteristics of sigmoid volvulus(SV) with multi-slice spiral computed tomography(MSCT) and improve the level of preoperative diagnosis in patients of SV. Methods: MSCT examinations were performed in 15 cases with sigmoid volvulus proved by pathology or colonoscope reposition, and the CT imaging characteristics were analyzed and summarized retrospectively. Results: The MSCT signs of 15 cases of SV included all 15 cases had sigmoid dilated, 4 cases showed intestinal damage(bowel wall thickening, mesenteric edema, mesenterium effusion and ascites etc.). 14 cases with inverted U-shape were showed on scanogram scanning, 13 cases of round belly sign, 11 cases of beak sign on cross-section scanning. MPR showed 10 cases of cross sign and 9 cases of whirl sign; Contrast-enhanced CT and CTA showed the enhancement of bowel wall weakened in 3 cases, 1 case of small vessel occlusion of mesentery, 2 cases of mesenteric artery rotation. Conclusion: The MSCT features of SV had some characteristics, especially had a great value in guideline for clinical therapy in the estimate of intestinal damage.

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2016 Vol. 25, No. 3