ISSN 1004-4140
CN 11-3017/P

2017 Vol. 26, No. 6

CT Theory
The Seismic Wave Numerical Simulation and Characteristics Analysis in Anisotropic Medium
GONG Ming-ping, ZHANG Jun-hua, LIU Wen-ge, LIU Yang, WU Xi-yuan
2017, 26(6): 661-668. doi: 10.15953/j.1004-4140.2017.26.06.01
Due to the anisotropy widely exists in underground rocks, and with the increasing of exploration precision, isotropic hypothesis of underground media can't be gradually content with the status quo, so the numerical simulation of the anisotropic medium is more important. This paper derived the elastic wave equation of anisotropic medium, summarized the source type, tackled the problem of the artificial boundary by PML method, and verified the numerical dispersion and stability conditions by snapshots. The results show that: 1) PML based on staggered grid can solve the problem of the artificial boundary; 2) reduce the spatial sampling interval is much better than reduce time sampling interval to suppress numerical dispersion and blindly reduce time sampling interval can reduce the operational efficiency of the numerical simulation; 3) there is quasi p-wave and slow quasi s-wave in the elastic wave field of anisotropic medium; 4) quasi p-wave front energy is stronger than quasi s-wave energy, quasi p-wave and quasi s-wave front are changed as parameters of anisotropic medium.
Viscoacoustic Reverse Time Migration by Adding a Regularization Term
TIAN Kun, ZHANG Xue-tao, LI Guo-lei
2017, 26(6): 669-677. doi: 10.15953/j.1004-4140.2017.26.06.02
The real geological medium is close to viscoelastic media in which seismic wave propagate with dispersion and attenuation. It is important to compensate the unwanted viscous effects in seismic processing. It is more accurate and physically more consistent to mitigate these effects in a wave-equation-based prestack depth migration. Historically, reverse time migration (RTM) based on directly solving the two-way wave equation has provided a superior way to image complex geologic regions. However, instability usually arises when considering compensation for absorption. Most researchers conduct high frequency filtering in wavenumber domain before or during wave field extrapolate in RTM to ensure stability. In this paper, we use viscoacoustic wave equation derived by Bai et al. (2013) to do Q-RTM and stabilize extrapolate by adding a regularization term. Compared with direct filtering, the regularization parameter can be space-varying. So this is suitable for severely variational regions. And we also find that source normalized cross-correlation imaging condition is more suitable in Q-RTM.
Evaluation and Analysis of Chronic Pulmonary Hypertension Model of Rats Based on CT and MRI
GAO Yan, SU Zhuang-zhi
2017, 26(6): 679-687. doi: 10.15953/j.1004-4140.2017.26.06.03
Objective: The aim of our study was to establish the rat models of pulmonary hypertension induced by monocrotaline. Using the micro CT and magnetic resonance (MR) right ventricular function imaging methods, we research the relationship between the evolution of right ventricular structure and function and the evolution of pulmonary artery pressure (PAH). Methods: Ninety-six Sprague-Dawley rats were randomly assigned into two groups: control group (n=48), and four PAH groups (n=48) caused by monocrotaline (MCT). Each group were divided into four groups (1 wk-PAH group, 2 wk-PAH group, 3 wk-PAH group, 4 wk-PAH group). We measured pulmonary artery pressure by right heart catheterization. After injection of MCT, we used the micro CT and MRI to measure the pulmonary artery diameter and the right ventricular function of the rats every week. All measurements of RV structure and function in model group were compared with pulmonary average pressure (PAP) using Pearson's correlation. Results: There were strong correlations between the parameters of RV structure and function in model group with the pulmonary average pressure (r=-0.823 for RV EF, r=0.732 and 0.803 for RV EDV and RV ESV, r=0.694 for the maximum inner diameter ratio of right ventricle to left ventricle). The diameter of main pulmonary artery was not correlated with mean pulmonary artery pressure (r=0.438). After injecting monocrotaline two weeks, the PAP, the maximum inner diameter ratio of right ventricle to left ventricle,, right ventricular eject fraction (RVEF), end-diastolic volume (EDV) and end-systolic volume (ESV) of right ventricle between rats in PAH and the control group showed no significant difference (P > 0.05). But three-four weeks after MCT injection, all these parameters were significant differences in PAH rats than in control group (P < 0.05). Conclusions: As the pulmonary arterial pressure increased in rats, the right ventricular function was gradually impaired. For the monitoring of chronic pulmonary hypertension model in rats, CT and MRI can accurately and rapidly measure the changes of parameters. The PAH can be indicated by observing parameter changes such as the pulmonary artery diameter, the right ventricular volume and cardiac output.
Spectral CT
Applied Value of Gemstone Spectral CT Imagine on Coronary Stents
ZHUANG Gao-ming, ZHONG Wei-feng, CHEN Xian-jie, LI Shu-ming, LAO Min-hua
2017, 26(6): 689-694. doi: 10.15953/j.1004-4140.2017.26.06.04
Objective: To investigate the application value of Gemstone spectral CT in coronary stents. Methods: CTA data of 45 patients with coronary stent implantation were collected, and the actual diameter of stent lumen was measured, and the difference of CT value between the stent lumen and adjacent vascular cavity was compared. Results: a total of 60 stents were found, which showed clear and no stenosis. 1, when the actual stent lumen diameter ≥ 2 mm, the stent lumen CT value measurement with good stability, the stent lumen CT value had no significant difference with the adjacent vascular cavity CT. 2, stent lumen diameter < 2 mm, the measurement of CT value of stent lumen is not stable and inaccurate, MPR images can still partially observe the stent lumen. Conclusion: Gemstone spectral CT has a higher diagnostic value for stents with a diameter ≥ 2 mm, and a definite diagnostic value for stent lumen diameter < 2 mm.
The Analysis and Gravity-Seismic Imaging in the Baiyun Sag Deep-water Hydrocarbon Area in the Northern South China Sea
QIN Qin, WU Shi-guo
2017, 26(6): 695-706. doi: 10.15953/j.1004-4140.2017.26.06.05
Baiyun sag, located in the marginal deepwater area of northern south China sea, is an important area for deepwater oil and gas exploration in China. The gravity-seismic imaging is the important methods to analyze the characteristics of the hydrocarbon source rock distribution, large structural trap, oil and gas accumulation and reservoir formation conditions. In this paper, through the calculation of gravity and gravity gradient inversion, and the analysis of the structure model of the seismic wave velocity Vs and seismic section, the free space gravity anomaly, bouguer gravity anomaly, horizontal, vertical gradient and density inversion images, the structure image of v wave velocity, high resolution seismic exploration profile image of the study area were achieved. The image of gravity data reveals that the strong negative abnormal in the center of Baiyun sag is associated with thicker deposition, basal ups and downs; the east of the sag is relatively high, related to Mesozoic residual strata; the north of the sag is abnormal as bandings, related to the of the concave-down basement where the slope extends to the oceanic basin. The sag and the south sag exist obviously layered negative residual density or relatively low density area, being the most reservoirs to holding oil and gas. The image of seismic data reveals: thin neck belt, outer edge uplift belt, ocean-land transition zone, and so on from north to south of Baiyun sag. During the epicontinental strong stretching thinning crust, there formed the sag structure of large delta-lacustrine source rocks sedimentary environment, and sediment source mainly comes from the north. As the strong thinning crust thin neck, there was obvious in Baiyun sag, resulting that the shelf slope break belt migrated from south to north to form the reservoirs: shelf edge of delta, deep-water gravity current channel and deep-water fan, and so on. Based on the analysis of high resolution seismic data for seismic section, we can identify many gas migration pathways, showing that shallow gas in Baiyun sag originate from deep strata.
A Method for Enhancing Resolution of Irregular Seismic Data in Curvelet Domain
KONG Xue, WANG De-ying, ZHANG Rui-xiang, ZHU Xue-juan, HU Qiu-yuan
2017, 26(6): 707-713. doi: 10.15953/j.1004-4140.2017.26.06.06
Considering the irregularity of seismic data and the limitation of traditional enhancing resolution method in single-channel seismic data, the problem of enhancing resolution is introduced into Curvelet domain and the method for enhancing resolution of irregular seismic data in curvelet domain is proposed. It utilizes the two-dimensional or high-dimensional support of curvelet basis function and the sparse representation of seismic data in curvelet domain, the problem of enhancing resolution of two-dimensional or high-dimensional seismic data is converted into the sparse promote solving with the constraint of L1-norm. Avoiding the problem of spatial consistency of the traditional enhancing resolution method, this method can enhancing the seismic resolution, suppressing random noise and restore the missing seismic traces, the completeness and resolution of seismic data are improved. Model and real data verify the correctness, validity and applicability of the method.
The New Technology by Using Multiple Wave Calculate Reflection Coefficient
LIU Yu-ping, YANG Zhi-cheng, Li Li-qing, ZHANG Bao-jin, LI Fu-yuan
2017, 26(6): 715-721. doi: 10.15953/j.1004-4140.2017.26.06.07
Conventional seismic data processing will be suppressing multiple waves as interference wave. Multiple waves are the feedback of reflected wave spread in the formation back and forth, so it carries information of reflection coefficient. Base on the causes of multiple waves, this article deduces reflection coefficient formula, that is the deconvolution of the first order multiple wave and the reflected wave. The theoretical model shows that the method is correct. The reflection coefficient is matched roughly with the reflected wave in processing of single channel seismic data. Because of the limitations of SNR, wavelet and deconcolution algorithm, this method needs further research.
Industrical CT
Effects of Relaxation Factor on ART Algorithm for Neutron CT
YIN Wei, TANG Bin, LIU Bin, SUN Yong, CAO Chao, HUO He-yong, LI Hang, WANG Sheng, WU Yang
2017, 26(6): 723-728. doi: 10.15953/j.1004-4140.2017.26.06.08
ART is one of significant and classical methods in CT reconstruction. Relaxation factor is an important parameter of ART. In this article, effect of relaxation factor on convergence speed and quality of reconstructed images has been researched, using the projections obtained from Cold Neutron CT facility of Mianyang Research Reactor, A chosen range of relaxation factor is given considering reconstruction efficiency and image quality, which has an important reference to neutron CT reconstruction.
Medical CT
Application of Iterative Reconstruction in Low-dose Chest CT Scans of Preschool Children
XIONG Shan, XU Lei, CHENG Jian-min, CHEN Bo, ZHENG Li, DAI Ting-ting, LIU Si-bin, HUANG Yuan-yi
2017, 26(6): 729-736. doi: 10.15953/j.1004-4140.2017.26.06.09
Objective: To explore the feasibility of iDose4 iterative reconstruction technique in low-dose chest CT scans of preschool children. Methods: One hundred and fifty patients underwent non-contrast chest CT examinations, they were randomly assigned into three groups: control group (standard dose protocol 120 k V, 50 mAs) (n=50); 25 mAs group (low dose protocol 120 k V, 25 mAs) (n=50); and 10 mAs group (low dose protocol 120 k V, 10 mAs) (n=50). Images from control group were reconstructed by FBP, and low-dose groups were reconstructed by FBP and iDose4. Subjective image quality was assessed by two associate chief physicians of radiology department in a blinded manner. Image quality and radiation dose of the 3 groups were compared and analyzed statistically. Results: Subjective and objective image quality in 25 mAs group with iDose4 compared with FBP was increased. Subjective and objective image quality in 10 mAs group with iDose4 compared with FBP was increased either. Subjective and objective image quality in 25 mAs with iDose4 was increased compared with control group. Subjective and objective image quality has no significant statistical difference between 10 mAs with iDose4 and control group. Effective dose in low dose groups 50 mAs and 25 mAs was decreased by 52.6% and 78.2% respectively. Conclusions: 50 and 25 mAs groups with iDose4 technique (iDose4-5) could obtain acceptable image quality in low-dose chest CT scans of preschool children while decreasing radiation dose.
The Relationship of CT Enhancement Magnitude between the Pathological Morphology and the Expression of VEGF in Esophageal Carcinoma
XING Yuan-yuan, ZHAO Jia-jia, CAO Hong-wei, WANG Sheng-lin, FENG Tao, LI Chun-hui
2017, 26(6): 737-743. doi: 10.15953/j.1004-4140.2017.26.06.10
Objective: To compare the expression of VEGF and the peak value of CT in 56 patients with esophageal cancer, and to study the correlation between them, and to provide reference for imaging diagnosis and early detection of esophageal cancer. Methods: Before operation, fifty-six cases of patients had an examination by routine and dynamic enhanced CT scan, get the CT scan value and enhance the peak value of each phase lesion. The positive expression of VEGF in esophageal mucosa and esophageal cancer tissues of control group was determined by immunohistochemical technique. Used statistical software SPSS 21.0 to process statistical analysis of all experimental data. Results: Enhancement of VEGF expression is related possibly to occurrence and metastasis of squamous cell carcinoma by lymph-vessel. These results showed that CT enrichment degree was not related to VGEF expression in esophageal mucosa of squamous cell carcinoma, indicating that CT enrichment degree in lesion do not respond directly lymph node metastases of carcinoma. Conclusion: Enhanced expression of VEGF may be a marker of squamous cell carcinoma and lymph node metastasi, The enhancement of the lesion in the CT scan could not reflect the metastasis of the tumor lymph nodes.
Volume Changes in Normal-Appearing Gray Matter for Nasopharyngeal Carcinoma by Using MR Voxel-based Morphometry
LUO Yan-ting, ZHANG Wei-dong, ZHONG Rui
2017, 26(6): 745-750. doi: 10.15953/j.1004-4140.2017.26.06.11
Objective: To assess the radiation-induced gray matter (GM) volume differences between nasopharyngeal carcinoma (NPC) patients who had and had not received radiotherapy (RT). Methods: Differences in GM volume between 20 NPC patients after RT and 16 control patients with newly diagnosed but not yet medically treated NPC was assessed by using magnetic resonance imaging voxel-based morphometry (VBM). Results: Patients who had received RT had GM volume decreases in the bilateral middle temporal gyrus, left superior frontal gyrus and left inferior occipital lobular, cluster size >100 voxels. Conclusion: GM volume deficits in bilateral temporal lobes in patients who had received RT. VBM can detect the earlier GM alteration which conventional MR can not detect.
Imaging Findings of Acute Bilateral Paramedian Thalamic Infarction Syndrome
WANG Xue-lu, DING Zhang-qing, DAI Lan-lan, LUO Hui, LIU Wen, DING Ai-lan, SUN Hui-fang
2017, 26(6): 751-759. doi: 10.15953/j.1004-4140.2017.26.06.12
Objective To analyze the images features of acute bilateral paramedian thalamic infarction syndrome. Methods: From October 2014 to January 2017, 8 patients with acute bilateral paramedian thalamic infarction syndrome confirmed clinically in our hospital were enrolled, and the clinical and images data were retrospectively analyzed. All patients underwent the first CT of the brain examination within 24 h, the first MRI examination of the brain was performed within 5 d. 3 cases had MRA examination data. Results Initial CT of the brain was unremarkable in 3 cases, suspicious bilateral paramedian thalamic infarcts in 4 case (presenting as suspicious or small low-density lesions), clear bilateral paramedian thalamic infarcts in 3 cases (presenting as somewhat symmetrical low-density lesions). MRI showed that the bilateral paramedian thalamus symmetrical distribution of the butterfly low or slightly low signal in T1 WI, high or slightly high signal in T2 WI, high or slightly high signal in FLAIR, high signal in DWI, and low signal in ADC. The lesion was characterized by high signal in DWI images on MRI. Follow-up of images showed the lesion was progressing in 4 cases. "V" shaped infarction of the midbrain could be seen in the course of the disease in 4 cases. Unilateral or bilateral posterior cerebral artery and its branched vessels stenosis could be seen on the images of the three patients underwent MRA examination. Conclusion Imaging examination methods, especially MRI, are of great value in the early diagnosis and differential diagnosis of acute bilateral paramedian thalamic infarction syndrome.
Correlation of Epicardial Adipose Tissue and Pericardial Adipose Tissue with Carotid Artery Plaque
LI Jing, QIAO Jian-min, WANG Jun-qi, GUO Qing-le, CHEN Shu-jun, ZHANG Wen-yan, ZHAO Yan-sheng, ZHAO Jing, LIU Jing-wang, LIU Shu-juan, ZHENG Bao-xia, WANG Long
2017, 26(6): 761-768. doi: 10.15953/j.1004-4140.2017.26.06.13
Objective: To explore the relationship among epicardial adipose tissue (EAT), pericardial adipose tissue (PAT) and carotid artery plaque. Methods: The routine health check-up data of 475 senior managers in Kailuan Corporation were collected and analyzed. All of them underwent chest CT scan examination, EAT and PAT volume were measured, according to the carotid ultrasound, the health check-up data was divided into plaque group (165 cases) and non-plaque group (310 cases), based on BMI, taking BMI < 24 as normal weight group, 24 ≤ BMI < 28 as overweight group, BMI ≥ 28 as obesity group, moreover, the correlation of EAT and PAT volume in normal weight group, overweight and obesity group with or without carotid plaque was studied respectively. Results: There were 45 cases with carotid plaques and 84 cases without plaques in normal weight group, 86 subjects with carotid plaques and 172 subjects without carotid plaques in overweight group, obesity group included 34 cases with carotid plaques and 54 cases without carotid plaques, the EAT and PAT volume of the subjects with carotid plaques in three groups were higher than those without carotid plaques (P < 0.05). Conclusion: EAT and PAT increase with obesity. After adjusting BMI, the EAT and PAT volume have a strong correlation with the formation of carotid plaques.
Comparative Analysis of the Effect of Multi-slice Spiral CT and Supersonic Echocardiography in the Treatment of Emergency Aortic Dissection
WU Yan-chun, PENG Xiao-bao, QIAN Bin
2017, 26(6): 769-774. doi: 10.15953/j.1004-4140.2017.26.06.14
Objective: To compare the value of the application of multi-slice spiral CT and echocardiography in the diagnosis of emergency aortic dissection. Methods: From December 2014 to December 2016, 61 patients with acute aortic dissection diagnosed by CT angiography in our hospital were retrospectively analyzed. All patients were examined by echocardiography and multi-slice spiral CT, and comparative analysis of two groups of diagnostic results. Results: Of all 61 patients with aortic dissection, 61 had a general abnormality, 41 had aortic valve abnormalities, 44 had aortic arch abnormalities, 45 had abnormal thoracic and abdominal aorta, and 6 had coronary artery abnormalities. The diagnosis of thoracic and abdominal aorta abnormalities and coronary artery abnormalities were 100.00%, which were 91.80%, 86.67% and 0.00% higher than those of echocardiography, the difference was statistically significant (P < 0.05). There was no significant difference between the two groups in the diagnosis of aortic valve abnormalities and aortic arch abnormalities (P > 0.05). Conclusion: Echocardiography in the diagnosis of aortic dissection is non-invasive, reproducible, and easy to operate. It can be used for the diagnosis of aortic arch abnormalities, Debakey type I aortic valve with high accuracy. Multi slice spiral CT has more advantages than echocardiography, which can be used to diagnose the abnormal branches of thoracic and abdominal aorta, coronary artery anomalies and so on.
The Effect of Contrast Medium Injection Rate on the Image Quality of Inferior Vena Cava Direct CTV
CAO Hong-wei, XING Yuan-yuan, CHOU Heng-zhi, ZHANG Dan, CAO Zhen-dong, WAN Li-ye, WANG Sheng-lin
2017, 26(6): 775-782. doi: 10.15953/j.1004-4140.2017.26.06.15
Objective: By comparing the image quality of the inferior vena cava (IVC) direct CT venography (CTV) using multi-detector computed tomography (MSCT), under different contrast medium injection rate conditions, to obtain optimal contrast medium injection rate, Methods: Using 64-detector row scanner (Sensation 64; Siemens), 30 patients who were suspected of inferior vena cava diseases underwent IVC direct CTV examination. Randomly divided into 5 groups, at the same conditions of contrast medium concentration (1: 6), liquid volume (unilateral liquid volume 200 mL), delay scan time (30 s) and without ligation of superficial veins of lower limbs, the contrast medium injection rate of each group was 2.5, 3.0, 3.5, 4.0, 4.5 mL/s respectively, then compare the image quality of each group. Result: All patients successfully completed the examination, the image quality of contrast medium injection rate 3.5~4.0 mL/s group is better than others, satisfied with clinical diagnostic purpose. Conclusion: IVC direct CTV using MDCT is feasible, at the same conditions of contrast medium concentration (1: 4), liquid volume (unilateral liquid volume 200 mL), and delay scan time (30 s) and without ligation of superficial veins of lower limbs, the optimal contrast medium injection rate is 3.5~4.0 mL/s.
Correlation Analysis of Imaging Score and Clinical Manifestation of Tibial Stress Fracture in Soldiers
ZHANG Qiu-yi, XU Kai, CHEN Kai, LIU Chen, WEN Lei
2017, 26(6): 783-790. doi: 10.15953/j.1004-4140.2017.26.06.16
Objective: To investigate the relationship between severity grade for radiography, magnetic resonance (MR) imaging, and computed tomography (CT); clinical severity; and recovery time from a tibial stress injury (TSI), as well as to evaluate inter-assessor grading reliability. Methods: A total of 34 cases of military soldier with TSI were included and mean age of all the participants were 19.1 yrs. All the TSI patients were evaluated by X-ray, MR imaging and CT by an orthopedist and a radiologist for the imaging severity. The clinical severity of these patients were assessed with an orthopedist. Statistical analyses were employed to explore the relationship between severity grade for radiography, magnetic resonance (MR) imaging, and computed tomography (CT); clinical severity; and recovery time from a tibial stress injury (TSI), as well as to evaluate inter-assessor grading reliability. Results: Negative associations could be found between X-ray (r=-0.529, P=0.029), MR imaging (r=-0.641, P=0.006), CT (r=-0.573, P=0.016) and clinical severity. No correlation was found between by X-ray, CT and recovery time. A correlation trend was found between MRI and recovery time (P=0.09). The best reliability was MRI (α=0.849), second was CT (α=0.779) and third was X ray (α=0.623). Conclusions: The clinical severity of TSI was negative associated with X-ray, MR imaging and CT grade score. No correlation was found between recovery time and with X-ray, MR imaging and CT grade score.