CT理论与应用研究

A Method for Directly Inverting Low Permeability “Sweet spot” by Using Elastic Impedance Equation

LI Bingying, ZHANG Jiajia, TU Qicui, LIU Jiang, ZHANG Guangzhi, ZHAO Chen, ZHU Shengwei, FAN Xianggang

2019, 28(4): 407-416. doi: 10.15953/j.1004-4140.2019.28.04.01

Abstract(272) PDF(7)

Abstract:
The "sweet spot" in low-permeability reservoirs is a very important geological target in the exploration and development of low-permeability oil and gas.It is of great significance to study the "sweet spot" prediction and identification methods for low-permeability reservoirs.Firstly, based on the definition of low-permeability "sweet plot", the sensitive elastic parameters of "sweet spot" are determined.On this basis, the elastic impedance inversion and "sweet spot" sensitive parameters prediction are proposed by the elastic impedance equation including the sensitive parameters of "sweet plot".This method reduces the cumulative error of indirect prediction of "sweet plot" and improves the accuracy of the "sweet plot" prediction.Combined with the Facies and fluids probabilities(FFP) technology, it achieves better results in the prediction of the "sweet plot" for the target area.

Comparative Study of Signal Time-Frequency Analysis Techniques Based on EMD,EEMD and CEEMD

SI Youqiang, GUO Runhua, SHI Pengcheng

2019, 28(4): 417-426. doi: 10.15953/j.1004-4140.2019.28.04.02

Abstract(416) PDF(21)

Abstract:
The time-frequency analysis method is widely used in various fields, especially in the field of engineering, and it is applied to the deformation of structures and components and internal damage detection.As an emerging nonlinear, HHT non-stationary time-frequency analysis technology has broad prospects in the field of detection and exploration.In this paper, the EMD, EEMD and CEEMD algorithms are analyzed.The Fourier transform and Hilbert-Huang transform of the synthesized signal are used to obtain the spectrum of the signal, Hilbert's yellow spectrum and marginal spectrum.Through comparative analysis, the advantages and disadvantages of the three methods are summarized.The results show that the EMD, EEMD and CEEMD methods are effective tools for nonlinear non-stationary signal analysis.

The Application of Accurate Seismic Processing in Shenhu Area

XU Yunxia, WEN Pengfei, ZHANG Ruwei, XUE Hua, CHEN Xi, ZHANG Xudong

2019, 28(4): 427-437. doi: 10.15953/j.1004-4140.2019.28.04.03

Abstract(203) PDF(9)

Abstract:
This article based on Shenhu Area's seismic data, in order to solve the problem of low imaging accuracy caused by rugged seafloor in the research area, this paper proposes a targeted treatment method: using combined multiple wave suppression technology to solve the problem of multiple wave attenuation in rugged seafloor, protruding the structural characteristics of middle and deep layers;using predictive deconvolution and zero phase processing technology to improve the resolution of shallow hydrate;using multiple iterative velocity analysis techniques to refine the accuracy of velocity analysis gradually, highlight the velocity reversal feature of hydrate.The final treatment results show that the targeted treatment technology proposed in this paper has achieved the expected results.The geophysical characteristics of hydrate related to BSR polarity reversal, amplitude blank zone and velocity reverse are clear, and the geological structural characteristics are clear such as faults, which are related to hydrate gas source and migration channel research.The result is helpful for interpretation experts to study hydrate enrichment and reservoir formation characteristics.

A Simple Method to Determine Linear Attenuation Coefficients of Some Metal Materials Using 9MeV Industrial CT System

WANG Kun, DENG Jun, WEI Bingjun, LUO Zhipeng, YU Yang

2019, 28(4): 439-446. doi: 10.15953/j.1004-4140.2019.28.04.04

Abstract(276) PDF(13)

Abstract:
X-ray linear attenuation coefficients have applications in choosing X-ray source, evaluating X-ray source penetration capability, investigating shielding performance of materials, etc.This work has been done to measure linear attenuation coefficients for Aluminum, Tungsten and Iron.Samples of different materials and different thicknesses were positioned between the X-ray source and the detector array and the central beam passed through the samples perpendicularly.The greyscale values of three channels in the detector array were read out with different materials and different thicknesses.The linear attenuation coefficients were calculated by plotting the log of the transmitted intensity against the varying in thickness.Compared with the results in NIST and another reference the linear attenuation coefficients obtained indicate that there is a good agreement between the experimental results and the results offered by the references.The proposed method can be adopted as an alternative method to measure the linear attenuation coefficients of materials.

Research on the Contrast Medium's Best Injection Combined with Low Tube Voltage in Aortic CTA

FU Chuanming, CHEN Lungang, CHEN Wen, XU Lin, WANG Sirong

2019, 28(4): 447-454. doi: 10.15953/j.1004-4140.2019.28.04.05

Abstract(213) PDF(4)

Abstract:
Objective: To explore the feasibility of contrast medium's best injection combined with low tube voltage in aortic CTA.Methods: Divided 80 patients who will be done aortic CTA examination into A, B two groups(n=40) by different contrast medium concentrations and tube voltages, while group A is divided into group A1, group A2(n=20) by different contrast medium concentrations and injection rate.Group A1: Injecting 302 mg I/mL Iohexol as contract medium, injection rate 4 mL/s, tube voltages 100 kV;group A2: Injecting 300 mg I/mL Iohexol as contract medium, injection rate 3.5 mL/s, tube voltages 100 kV;group B: Injecting 350 mg I/mL Iohexol as contract medium, injection rate 3.5 mL/s, tube vantage 120 kV;Other scanning parameters: Injection contrast dose, reconstruction mode, automatic tube current regulation technologies are consistent.Two independent sample tests are used(Mann-Whitney U test for non-normal distribution) to compare the clinic data, radiation dose of CT, subjective and objective evaluation of image quality in the two groups.Results: There was no significant difference in age, gender, body mass index(BMI) between group A and group B(P>0.05);there was also no statistical significance in the subjective and objective evaluation of image quality(P>0.05).The CNR of group B was better than group A, which met the diagnostic requirements, the CT values of the aortic trunk and branches were all>300 HU.There was statistically significant differences between group A and group B in radiation dose and iodine content(P<0.01).Effective radiation dose(ED) of group A was 17.73%lower than that of group B, and iodine content was 14.29%lower.Conclusion: injection of 300 mgI/mL Iohexol solution and injection rate of 3.5 mL/s combined with low tube voltage(100 kV) obtained satisfactory image quality in aortic CTA examination, providing accurate diagnostic basis for clinical practice, which not only reduced the radiation dose, but also reduced the iodine content.

To Investigate the Application of Low-dose Contrast Agent Combined with Low Monitoring Threshold in CTA of the Head and Neck

YU Tao, DAN Hua, JIANG Wenwen

2019, 28(4): 455-461. doi: 10.15953/j.1004-4140.2019.28.04.06

Abstract(235) PDF(5)

Abstract:
Objective: To investigate the application of Philips Brilliance ICT with low-dose contrast agent combined with low monitoring threshold in CTA of the head and neck.Materials and Methods: Sixty patients requiring CTA of the head and neck in our hospital were selected and randomly divided into group A(observation group) and group B(experimental group), which received different injections and scanning scheme, respectively.A(observation group) contrast agent 60 mL, saline 40 mL, Monitoring Threshold 150 HU;B(experimental group) contrast agent 40 mL, saline 40 mL, Monitoring Threshold 90 HU;injection rate of both groups were 5.0 mL/s, monitoring the aortic arch.The images in the 2 groups were subjectively evaluated(visual observation) and objectively evaluated(the measurement of CT values of the superior vena cava, aortic arch, left and right common carotid artery, left and right middle cerebral artery), respectively, for the analysis of the quality of images.Results: (1) The subjective evaluation showed that all images in group A and group B could meet the diagnostic requirements.In group B, the contrast agent residue in the superior vena cava reduced significantly.(2) The scores of images quality in group A and group B presented no statistical significance(P>0.05).3.Comparison of the CT values of the superior vena cava, aortic arch, left and right common carotid artery, left and right middle cerebral artery between group A and group B showed statistical significance(P<0.05).Conclusion: Although the application of Philips Brilliance ICT with 40 ml of contrast agent combined with monitoring threshold of 90 HU in CTA of the head and neck shows differences in CT values of the images, the quality of the images can fully meet the clinical diagnostic requirements.In addition, with the quality of images ensured, the contrast agent dose and contrast agent residue in the superior vena cava are reduced.

The Relationship between Pancreatic Steatosis and Framingham Cardiovascular Risk Score in Patients with Type 2 Diabetes Mellitus

SUN Pengtao, DOU Xuechao, SUN Xiaoli, ZHAO Tong, WEI Hailiang, WEN Tingguo, WANG Rengui

2019, 28(4): 463-470. doi: 10.15953/j.1004-4140.2019.28.04.07

Abstract(271) PDF(7)

Abstract:
Objective: To investigate the association of pancreatic steatosis with Framingham risk score(FRS) in patients with type 2 diabetes mellitus(DM).Methods: Patients with type 2 DM undergoing abdominal CT in our hospital were enrolled in the study from January 2018 to February 2019.CT attenuation of pancreas and the spleen was measured on nonenhanced CT images, and CT attenuation indexes was calculated(The difference between pancreatic and splenic attenuation and the ratio of pancreas-to-spleen attenuation).Pancreatic steatosis was defined as pancreatic attenuations below median levels.The demographic data and biochemical indexes were collected from all the participants.According to FRS, all patients were divided into low-risk, mid-risk and high-risk group.Kruskal-Wallis rank test or Chi-square test was used to assess differences of clinical and imaging data in each group.Spearman correlation was used to assess the correlation between CT attenuation of pancreas, CT attenuation indexes and Framingham risk score.Multiple Logistic regression analysis was used to analyze the related factors of Framingham risk score.Results: Totally 161 consecutive patients with type 2 DM were included in this study.There were significant differences in CT attenuation of pancreas(Z=11.320, P=0.001), P-S(Z=0.324, P=0.002) and P/S(Z=9.908, P=0.002) between low risk group and higher risk group.There were significant differences in CT attenuation of pancreatic head, body and tail in high-risk group(Z=10.239, P=0.006).Spearman correlation showed that CT attenuation of pancreas(r=-0.312, P<0.0001), P-S(r=-0.280, P=0.0003) and P/S(r=-0.287, P=0.0002) were negatively correlated with Framingham risk score.After adjusting for confounding factors, CT attenuation of pancreas(OR=0.950, 95%CI: 0.910-0.991;P=0.018), P-S(OR=0.943, 95%CI: 0.895-0.992;P=0 024), P/S(OR=0.040, 95%CI: 0.003-0.571;P=0.018) and pancreatic steatosis(OR=2.825, 95%CI: 1.150-6.940;P=0.024) were still associated with the risk of cardiovascular events.Conclusion: CT attenuation of pancreas and CT attenuation indexes were independently associated with risk score of cardiovascular events in patients with type 2 DM, suggesting that pancreatic steatosis may indicate the risk of cardiovascular events in these patients.

Comparison in Localization of Pancreatic Insulinoma by the Multiparameter of Dual Energy Spectral CT Imaging

ZHANG Jing, LI Honglei, ZHANG Ting, BU Yulian, CHEN Xiaoyan, FANG Weihuan, XU Jingci, PAN Zilai, CHEN Kemin, LI Weixia, SHAO Dandan, LIN Xiaozhu, YAN Fuhua

2019, 28(4): 471-476. doi: 10.15953/j.1004-4140.2019.28.04.08

Abstract(257) PDF(9)

Abstract:
Objective: To compare the multiparameter of dual energy spectral CT imaging in localization of pancreatic Insulinoma.Materials and Methods: 42 patients were included in this study with underwent the dual-phase DEsCT imaging.Their CT images were interpreted retrospectively by two radiologists.All the patients had been confirmed pathologically.Results: 70 ke V mono-energy imaging detected 30, 20 of 42 tumors, in arterial phase and venous phase, separately;the optimal CNR monochromatic imaging detected 38, 27 of 42 tumors, in arterial phase and venous phase, separately;the iodine density imaging detected 38, 29 of 42 tumors and 39, 32 of42 tumors detected with the combination of the three kinds of images, in arterial phase and venous phase, separately.71.4%(30/42), 90.5%(38/42), 90.5%(38/42), 92.9%(39/42) and 47.6%(20), 64.3%(27), 69%(29), 76.2%(32).Conclusion: The optimal CNR monochromatic imaging has highest sensitivity in localization of insulinomas compared with the 70 ke V mono-energy imaging and the iodine density imaging.The combination of monochromatic image and iodine density image can improve the sensitivity of locating insulinomas.

Diagnostic Value of CT Value of Creeping Fat around Intestinal Tube for Crohn's Activity

GAO Yun, GUAN Xueni, RONG Lan, ZHOU Lei, LIANG Zonghui

2019, 28(4): 477-484. doi: 10.15953/j.1004-4140.2019.28.04.09

Abstract(314) PDF(4)

Abstract:
Objective: Investigate the CT value changes of creeping fat around the intestinal segment in Crohn's disease(CD).Methods: From January 2010 to March 2019, 31 patients with active CD(study group) and 31 age and gender matched inactive CD patients/healthy people(control group) were enrolled in the study.The people of study group and control group were tested for CT values of mesentery near the inflammatory intestinal wall, including CT values in plain scan, arterial phase, venous phase and delayed phase.Clinical data including enteroscopy and its pathological results, and clinical immunosuppressive therapy were collected.Results: There were 31 patients(26 males and 5 females) with active Crohn's disease(CD) in the study group.There were 31 patients(22 males and 11 females) in control group.The CT value of creeping fat in patients with Crohn's disease in active stage is higher than that in inactive CD patients/healthy people, and there may be sustained mild enhancement after enhancement over time.Conclusion: The creeping fat along the mesenteric border of bowel inflamed segments of CD can be denser and continuously strengthened during the active stage of the disease, so the change of CT value of the creeping fat around the intestinal tube has diagnostic value for Crohn's disease activity.

The Diagnostic Value of Gd-Eob-Dtpa Enhanced MRI in Hepatocellular Carcinoma in Liver Cirrhosis

HUANG Jieling, LI Yuanzhang, LI Liangjie, YUAN Qinghua

2019, 28(4): 485-492. doi: 10.15953/j.1004-4140.2019.28.04.10

Abstract(308) PDF(7)

Abstract:
Objective: to explore the diagnostic value of gd-eob-dtpa enhanced MRI for liver cancer in the background of liver cirrhosis.Methods: the MRI findings of 20 patients with hepatocellular carcinoma confirmed by pathology were retrospectively analyzed.Results: 25 nodules were found in 20 patients with hepatitis b cirrhosis.A total of 22 nodules were diagnosed as hepatocellular carcinoma by MRI plain scan and classic phase iii dynamic enhancement scan, and the other 3 nodules were diagnosed as RN or DN nodules of cirrhosis.Twenty cases of liver cancer were diagnosed by high-b DWI imaging, and the other five cases were benign lesions.Twenty-five cases of liver cancer were diagnosed by enhanced MRI with gd-eob-dtpa.The diagnostic accuracy of plain MRI and classic phase iii dynamic enhanced MRI, high-b-value DWI imaging, gd-eob-dtpa enhanced MRI for hepatocellular carcinoma was 88%, 80%, and 100%, respectively, with statistically significant differences(P<0.05).ROC curve showed that the sensitivity, specificity and accuracy of gd-eob-dtpa enhanced MRI in the diagnosis of liver cancer were significantly higher than that of plain MRI, classical phase iii dynamic enhancement and high-b-value DWI alone, and the area under the curve(P<0.05).Conclusion: gd-eob-dtpa enhanced MRI can improve the diagnostic efficacy of liver cancer in the context of liver cirrhosis, which is worthy of clinical application.

Application of Enhanced CT in Assessing the Source of Active Haemorrhage in Patients with Abdominal and Pelvic Trauma

LIU Tao, YAN Long, WU Guangyao, MING Jianzhong, XIANG Chengxian, SHANG Xubin

2019, 28(4): 493-498. doi: 10.15953/j.1004-4140.2019.28.04.11

Abstract(258) PDF(4)

Abstract:
Objective: To assess the ability of contrast enhanced computed tomography(CECT) to detect active haemorrhage in abdominal and pelvic trauma patients, using angiographic findings as paired gold standards.Methods: A retrospective analysis of patients with abdominal and pelvic trauma from January 2016 to February2019, all patients underwent abdominal-pelvic enhanced CT after admission, and DSA angiography or embolization within 24 hours of injury, all CT and DSA images were judged by two relevant professional physicians(one of whom is the deputy chief physician).we obtain sensitivity, specificity, positive predictive value, negative predictive value of CT detect hemorrhage by compared with DSA images(as gold standard).Results: During the periods, 33 adult trauma patients sustaining enhanced CT scan of abdominal and pelvic followed by angiography.Ten patients were negative for extravasations from either of the tests.Twenty of 33 patients had both positive CT scans and angiograms.Only one patient with positive CT scans did not have bleeding on angiogram.Two with positive angiograms did not show any extravasations of contrast on CT scan.The sensitivity(SE), specificity(SP), positive predictive value(PPV) and negative predictive value(NPV) of CECT in detecting active abdominopelvic haemorrhage, as compared to DSA, were 90.9%, 90.9%, 95.2% and 83.3%, respectively.Conclusions: Contrast enhanced CT shows high sensitivity and positive predictive value for the detection of active haemorrhage in patients with blunt abdominopelvic trauma, when compared with DSA, and can be used to triage patients for management.

Diagnostic Value of 64-slice Spiral CT Post-processing on Ileocecal Lesions

FU Xi, HE Weihong, XIE Le, FANG Tingsong, CHEN Shaoluan, LIANG Zhenhua

2019, 28(4): 499-504. doi: 10.15953/j.1004-4140.2019.28.04.12

Abstract(245) PDF(5)

Abstract:
Objective: Analyze the imaging characteristics of 64-slice spiral CT in benign and malignant ileocecal lesions and the diagnostic value of post-processing techniques.Methods: 53 cases of ileocecal lesions confirmed by operation and pathology were collected.All cases underwent CT plain scan and enhanced scan.The imaging characteristics of benign and malignant ileocecal lesions were analyzed and the diagnostic effects of original axial image and post-processing image were compared.Results: The accuracy of localization and qualitative diagnosis of original axial images combined with MPR/CPR was higher than that of original axial images, and the difference was statistically significant(P=0.03;P=0.04).MPR and CPR can clearly and completely display the relationship between internal and external structures of ileocecal lesions and adjacent organs, and improve the accuracy of diagnosis of ileocecal lesions.Conclusion: 64-slice spiral CT can display ileocecal lesions accurately and intuitively.The combination of original axial images with MPR/CPR images can improve the diagnostic accuracy of ileocecal lesions.

MRI Findings of Uterine Carcinosarcoma

JIANG Xiaodong, FENG Feng

2019, 28(4): 505-512. doi: 10.15953/j.1004-4140.2019.28.04.13

Abstract(249) PDF(4)

Abstract:
Objective: To investigate the MRI features of uterine carcinosarcoma, to improve the accuracy of MRI diagnosis.Methods: The MRI findings of 7 cases of uterine carcinosarcoma confirmed by pathology from January 2017 to December 2017 were analyzed retrospectively.Results: The volume of the uterus increases and the lumps in the uterine cavity increase.Larger size of lesion(6 cases with maximum diameter greater than 5 cm).Irregular form, in a leaf shape, the boundaries are not clear.MRI features: Flat sweep T₁WI is equal low or mixed signal, T₂WI is equal, slightly higher mixed signal, partial bleeding.The real part of the lesion DWI is high signal, the ADC diagram is low signal, the average ADC value is(1.105±0.136) ×10^-3 mm².Enhanced scanning uneven enhancement, the venous phase and the delayed phase continue to strengthen, there was no enhancement of internal hemorrhage and cystic necrosis.Some tumors invade the cervix, and it is released into the neck tube.Part of the pelvic and retroperitoneal lymph nodes.Conclusion: Size and shape of the lesion, DWI high signal, higher ADC value, early and continuous strengthening, contribute to the diagnosis and differential diagnosis of uterine carcinosarcoma, MRI has a more important significance on the depth and extent of tumor invasion.

Dual-energy CT in Gout: Advances in Diagnosis and Assessment

YE Kunlin, LUO Liangping, CHENG Guanxun, XIANG Ziyun

2019, 28(4): 513-518. doi: 10.15953/j.1004-4140.2019.28.04.14

Abstract(285) PDF(9)

Abstract:
Gout is a kind of metabolic disease caused by the deposition of uric acid crystals, whose acute present as joint redness, swelling, fever and pain.It can develop into a chronic disease.And long-term recurrent attacks may be accompanied by a variety of serious diseases, which can cause severe impacts on health.This article introduces the principle of dual-energy CT imaging, and the diagnostic value of dual-energy CT in acute gout and the potential application in evaluating the efficacy of chronic gout, and the known artifacts and corresponding measures.

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2019 Vol. 28, No. 4