CT理论与应用研究

Finite-difference Modeling and Wave-field Analysis of Rayleigh Surface Wave in Viscoelastic Media

WANG Changbo, TIAN Kun, LIU Libin, LI Guolei, ZHANG Xuetao

2019, 28(2): 153-166. doi: 10.15953/j.1004-4140.2019.28.02.01

Abstract(275) PDF(4)

Abstract:
Rayleigh surface wave has been used to research the character of shallow subsurface widely, and the real geological medium is close to viscoelastic media. This paper models Rayleigh wave in viscoelastic media with planar free surface by using the staggered-grid finite-difference method based on the generalized standard linear body. And we compared the results of the viscoelastic media with the elastic one. In this paper the Levenberg-Marquarat algorithm is adopted to compute the relaxation time to fitting the constant Q model firstly. Acoustic-elastic boundary approximation method is used to implement free surface conditions. The condition that transverse stress on and under the free surface remain continuous is considered by keeping the shear modulus unchanged. And for other boundaries the unsplit multiaxial convolutional perfectly matched layer is chosen to absorb waves. Then the wave fields are calculated in several typical models. The comparisons of numerical and analytical solutions confirm the veracity and validity of the method in this paper. And the computed results indicate that viscoelasticity can influence the surface wave dispersion. So the viscoelastic factors should be considered in the surface wave exploration.

Microstructure Analysis of Deformation Band in Porous Sandstone Based on Three-dimensional X-ray Microscope

QU Fang, LIAN Chengbo, CHAI Zhenhan, REN Guanxiong

2019, 28(2): 167-174. doi: 10.15953/j.1004-4140.2019.28.02.02

Abstract(328) PDF(5)

Abstract:
Deformation bans in porous sandstones is of great significance in revealing their related geological processes and engineering applications. Its microstructure is the key point of its related scientific and engineering research. Conventional methods of rock micro structural analysis have some limitations in comprehensively analyzing the internal microstructures of rocks. Three-dimensional X-ray micro-imaging technology developed in recent years can acquire three-dimensional fine digital images of micro-scale inside rocks nondestructively. It is an effective means to establish and analyze rock microstructures. High resolution three-dimensional micro structural image of deformation band in porous sandstones was established by scanning the deformation band with three-dimensional X-ray microscopy. The micro structural characteristics of deformation band in porous sandstones were analyzed by using continuous slice images. Based on the analysis of micro-occurrence zones and particle breaking process of deformation band, a complete time series of grain breaking-broken particles and residual broken particles rearrangement-local particle breaking zones-weak particle breaking deformation zones-strong particle breaking deformation zones-strong and weak particle breaking deformation zones-cluster deformation zones was established.

Upper Mantle Velocity Structure and Its Dynamic Implications beneath the Tibetan Plateau from Triplicated Seismic P Waveforms

LV Miaomiao

2019, 28(2): 175-186. doi: 10.15953/j.1004-4140.2019.28.02.03

Abstract(300) PDF(7)

Abstract:
Due to its complex structure and evolution history, Tibetan plateau has always been a focused region for study continental collision, tectonic movement and its geodynamics. Based on the the vertical P wave records from a selected earthquake recorded by CDSN (Chinese Digital Seismic Network) and temporary seismic stations, the high resolution upper mantle structures beneath the Tibetan Plateau including the Lhasa Terrane,south Qiangtang terrane and Songpan-Ganzi terrane are obtained by triplication waveform fitting technique. Our results show that: (1) The high velocity anomaly observed at the bottom of MTZ (mantle transition zone) beneath Lhasa and south Qiangtang terranes are interpreted as the remnants of the subducted Indian slab,and these cold material depressed the post-spinel phase transition of 660km discontinuity by 3~8km. The high velocity anomaly can also be observed beneath Songpan-Ganzi terrane, which may be caused by the delamination of thickened Eurasian lithosphere. It suggests that the influence of Indian slab subduction has reached the MTZ, and the subduction front beneath the Tibetan Plateau is located near the Bangong-Nujiang suture. (2) From Lhasa, south Qiangtang to Songpan-Ganzi terranes, the upper-mantle velocities over 200km decreases gradually along the N-S profile, and the high-velocity lid even disappears in Songpan-Ganzi terrane. Influenced by the small-scale mantle convection or thermal instability, the thickened Eurasian lithosphere beneath south Qiangtang and Songpan-Ganzi terranes was delaminated, and the lithosphere was thinned and weakened, resulting in the low velocity of upper mantle in Qiangtang and the absence of high-velocity lid in Songpan-Ganzi terrane. Some of the delaminated lithosphere maybe now sitting atop of the 410km discontinuity, causing the uplift of 410km discontinuity by about 10km and others may have penetrated into the MTZ, characterized by the high velocity in the lower MTZ beneath Songpan-Ganzi Terrane. Low temperature causes the depression of 660km discontinuity by about 8km, resulting in the thickening of the MTZ.

Detection Technology of Concealed Structure of Hydraulic Engineering Based on the Fusion of Nondestructive Multi-source Heterogeneous Data

XU Yunqian, YUAN Mingdao, CHEN Xiaowen, SHI Yongsheng, LIU Jianwen, YANG Wenbin, LINE Yueqi

2019, 28(2): 187-194. doi: 10.15953/j.1004-4140.2019.28.02.04

Abstract(318) PDF(7)

Abstract:
This paper introduces the different detection methods and characteristics of the exposed structure and concealed structure of hydraulic engineering and the status quo of relevant research and exploration. In this paper, the application of the hidden trouble detection of the Zhongxingou East Gate of the University of Macau in Hengqin New Area is presented. Take the method of 3d laser scanning and ground-penetrating radar technology. This paper discusses and studies the fusion application of multi-source heterogeneous detection data of hidden structure of hydraulic engineering.

Algebraic Reconstruction and Structure Recognition for Ultrasound CT Image on Physical Model

CHEN Xuananga, ZHANG Shia, LI Zhiyonga, WU Dib, WANG Chengyonga, WU Faena, CHEN Lichenga

2019, 28(2): 195-204. doi: 10.15953/j.1004-4140.2019.28.02.05

Abstract(293) PDF(11)

Abstract:
In this paper, a two-dimensional physical model made of "wood board" and "plexiglass board" is adopted, and three square holes of different sizes and positions, filled with gypsum are added to the model. The same observation system is arranged for the two physical models to form the same ray mode. Under the condition of equally spaced rectangular pixels, the integration step size of each ray (the length of the ray segment passing through a single pixel) is a constant. The travel time data of each transmitted wave ray (i.e. the "observed value" of the Radon transform line integral) is collected by the ultrasonic instrument along the designated ray. The "algebraic reconstruction method" (ART addition modified iteration method) is used to solve the discretized equations of the Radon transform, and the CT digital image of the two-dimensional physical model is reconstructed. In the reconstructed model CT digital image, the existence and location of "gypsum hole" can be effectively identified, which verifies the effectiveness of "algebraic reconstruction" CT imaging technology and its recognition of model structure. This paper is basic research of addition modified iteration ART and provides practical application reference for those who interest in" Algebraic Reconstruction Technique".

Application of Industrial Computerized Tomography in Testing of Fault Magnetic Coil

PAN Guangyong, ZHANG Minxia, BAO Yilang, ZHANG Hangbin

2019, 28(2): 205-212. doi: 10.15953/j.1004-4140.2019.28.02.06

Abstract(329) PDF(7)

Abstract:
The internal structure analysis of the magnetic coil was using industrial CT to avoid the difficulty of disassemble magnetic coil during failure analysis. The computed tomography (CT) imaging characteristics for internal defects of resin matrix composite products were studied and analyzed. The results show that industrial CT is able to effectively detect various defects of the fault magnetic coil such defects as breakage of enameled wire, inadequate installation of components, fusing of enameled wire, winding deformation, porosity in the envelope, excess wire or metal impurities, et al. industrial CT can accurately determine t the location and geometry of the defects. The analysis of Industrial CT application has guidance significance for improving the quality of magnetic coil and production technology.

Optimization of the Measurement of CT Perfusion Parameters of Rectal Carcinoma Recurrence

HU Juan, TANG Guangjian, YANG Xuedong, WANG Xiaoying, LIU Jing, GUO Xiaochao

2019, 28(2): 213-220. doi: 10.15953/j.1004-4140.2019.28.02.07

Abstract(273) PDF(4)

Abstract:
Objective: To optimize measurement of CT quantitative perfusion parameters for local recurrence and postoperative scar of rectal carcinoma. Method: Ten consecutive rectal carcinoma patients who had undergone Mile's operation were recruited. They were suspected recurrence of cancer because of symptom or review examination. A cine-mode CT perfusion acquisition was performed covering each lesion. The acquisition started 10s after intravenous injection of contrast material (70mL) and lasted 60s. On a perfusion dedicated workstation, regions of interest (ROI) were placed in different ways which contained fixed ROI (24mm²), hot spot (single voxel), hot zone (24mm²) and whole mass. Blood flows (BF), blood volume (BV), mean transit time (MTT) and permeability-surface product (PS) were calculated. Perfusion functional maps were obtained. With the cross-section histogram tool of workstation, the mean value of the highest 5%, 10%, 20%, 40% and 60% of BF, BV, MTT and PS were acquired respectively. All the parameters were measured twice separated by two weeks. All patients with 11 masses received CT guided needle biopsy within one week. Long-term follow-up confirmed the character further. All the perfusion parameters by each method were compared by One-Way ANOVA and two times measurements were compared by Paired-Samples t Test. Results: There were ten patients and 11 lesions(recurrence group: n=6; scar group: n=5). Perfusion parameters varied obviously of different ways of measurement. The lowest value was acquired by whole mass measurement, while the highest value was acquired by the highest 5% measurement. BF, BV, MTT and PS of recurrence group were higher compared with scar group (P<0.05) except the MTT using fixed ROI measurement,MTT and PS using hot spot measurement (P>0.05). There was no statistical difference of perfusion parameters between the first and second measurements (P>0.05) except PS using hot zone (P<0.05). And the whole mass and highest ratio perfusion parameters were more stable (r ≥ 0.963, P<0.05). Conclusion: Compared with conventional measurement, the highest ratio perfusion value obtained by the cross-section histogram tool is more useful, objective and stable for differentiation of local recurrence and postoperative scar of rectal carcinoma. The recommendatory ratio was the highest 5%.

The Influence of Different Noise Indexes on Chest CT Image Quality for Patients with PCP

XIA Zhenying, WU Dan, YU Jianan, LI Siyuan, SONG Wenyan

2019, 28(2): 221-228. doi: 10.15953/j.1004-4140.2019.28.02.08

Abstract(303) PDF(3)

Abstract:
Objective: To evaluate the application of different noise index combined with Z-axis automatic tube-current modulation technology, guided by body mass index (BMI), in CT chest scanning of AIDS patients with PCP. Methods: A total 30 cases of AIDS patients with PCP underwent routine dose and low dose scanning protocol with Z-axis automatic tube current modulation. The noise index (NI) for standard protocol was set to 10, the noise index (NI) for low dose protocol was set to 20, the range of tube current was set to 30-500mA, the tube voltage was 120kV, the NI of control group was 10, and the NI of low-group was 20. The volume CT dose index (CTDIvol) and dose length product (DLP) during CT scanning were recorded and the effective dose (ED) was calculated. The noise value was measured at pulmonary tip level, aortic arch level and pulmonary base level under the longitudinal window. The quality and subjective noise of CT images were evaluated by the 5-point system. Results: The subjective scores of the two groups reached the standard of clinical diagnosis. When NI was 20, the noise was higher than that when NI was 10, and the difference between the two groups was statistically significant (P<0.05). When NI was 20, the mean CTDIvol, DLP and ED decreased by 63.20%, 63.48% and 63.49% respectively compared to the low-dose group, and the difference between two groups was statistically significant (P<0.05). Conclusion: Under the guidance of BMI, by using Z-axis automatic tube-current modulation technology, the radiation dose of AIDS patients combined with PCP can be significantly reduced by setting a reasonable NI, while the quality of CT image meets the requirements of clinical diagnosis.

The Study of Accurate Liver Volume Measurement by IQQA-liver Auto Analysis Software

HUA Chenchen, LIU Yao, YIN Qihua

2019, 28(2): 229-235. doi: 10.15953/j.1004-4140.2019.28.02.09

Abstract(341) PDF(5)

Abstract:
Objective: To compare the Accuracy and stability of liver volume measurements by MDCT and MR by IQQA-liver auto analysis software. Method: (1) 12 rabbits were scanned by MDCT and MR FIESTA and LAVA sequences, Then kill the rabbits and measure the rabbits, liver immediately (actual liver volume ALV) by means of water displacement. Compare the liver volumes measured by MDCT, MR and water displacement. (2) Repetitive study: repeat measure the liver volumes of all the rabbits. Results: (1) The liver volumes of rabbit measured by MDCT, MR FIESTA and LAVA sequences were (126.4±35.8) cm³, (125.0±35.4) cm³, (125.8±35.7) cm³, had a significant correlation (r=0.997, 0.997, 0.998, P<0.05) with the liver volume by means of water displacement which was (126.6±36.4) cm³. Liver volume with MDCT, MR FIESTA and LAVA sequences and displacement of water was good consistency by Bland-Altman method. (2) Repetitive study: repeated measures of liver volumes of rabbits and patients at different time by each same operator, the ICC were 0.995, 0.985; measures of liver volumes of rabbits by two operators at each time, the ICC were 0.996, 0.987. Conclusion: MDCT and MR can provide accurate information in the measurement of the liver volume used by IQQA-Liver auto analysis software, with high reliability and reproducibility.

Dynamic Contrast-enhanced MRI Parameters Measurements in Epithelial Ovarian Carcinoma: Comparison of ROI on the Reproducibility of the Parameters

MAO Mimi, FENG Feng, LI Haiming

2019, 28(2): 237-245. doi: 10.15953/j.1004-4140.2019.28.02.10

Abstract(281) PDF(4)

Abstract:
Objective: The study aimed to investigate the comparison of different regions of interest (ROI) on reproducibility of semi-quantitative parameters in dynamic contrast-enhanced MRI (DCE-MRI) of epithelial ovarian cancer. Methods: DCE-MRI data of 60 epithelial ovarian cancers, confirmed by surgery and histopathology, were analyzed retrospectively. Four DCE-MRI semi-quantitative parameters, including the peak time (TTP), the maximum concentration (MAX), the area under the concentration time curves (AUC) and the maximal slope (MS), were measured with postprocessing software. The two physicians used the irregular shape, the circular shape and the rectangular method to delineate the ROI on the semi-quantitative AUC pseudo-color image. The data were calculated by two observers independently, observer 1 reevaluated all of the images, which were presented in a different order, one month after the first session. The differences of DCE-MRI semi-quantitative values with different ROI methods, which can be compared in One-Way ANOVA.Intra and interobserver agreement, were evaluated using the intraclass correlation coefficient (ICC), coefficient of variation (CV) and Bland-Altman analysis. Results: There was no significant difference among the three groups (P>0.05). Intra- and interobserver reproducibility were excellent by polygon ROI, The values of ICC in the intraobserver and the interobserver were (0.975~0.985) and (0.961~0.984), respectively; CV were (2.73~4.21) and (3.48~4.86), respectively. The results showed that polygon repeat the measurement of consistency in the range of small, good accuracy. Conclusions: Epithelial ovarian cancer with different ROI had no significant effect on the semiquantitative parameters, and showed a high degree of consistency.

Analysis of CT Differential Diagnosis of Esophageal and Gastric Syndromes with Different Pathological Types

DENG Zhiqiang, TANG Min

2019, 28(2): 247-254. doi: 10.15953/j.1004-4140.2019.28.02.11

Abstract(209) PDF(5)

Abstract:
Objective: To explore the differential diagnosis effect of energy spectrum on the pathological type of esophagogastric junction cancer. Methods: We retrospectively analyzed the clinical data of 116 patients with esophageal and gastric adenocarcinoma who were admitted to our hospital between January 2015 and January 2018. Of these patients, 64 were adenocarcinomas and 52 patients were squamous cell carcinomas. There were 27 well-differentiated cases, 45 moderately differentiated and 44 poorly differentiated. All patients underwent spectral CT scans. The ROI iodine concentration (IC), effective atomic number (Eff-Z), water concentration (WC), energy spectrum curve slope (λ_HU) in arterial and venous masses were compared between adenocarcinoma and squamous cell carcinoma patients, and the degree of differentiation was compared. In patients with arterial and venous masses, IC, Eff-Z, WC, and λ_HU. Analyze the differential diagnosis efficacy of energy spectrum CT on the pathological type and differentiation of esophageal and gastric junction cancer. Results: The comparison of IC, Eff-Z, WC, and λ_HU in the arterial and venous phases of adenocarcinoma and squamous cell carcinoma was performed. Results: (1) There was no significant difference in WC between arterial phase and venous phase in the two groups of patients. (P>0.05); (2) Compared IC, Eff-Z, and λ_HU in arterial phase and venous phase between the two groups of patients were statistically significant (P<0.05), IC and Eff-Z in arterial phase and venous phase in adenocarcinoma patients. λ_HU were higher than squamous cell carcinoma patients. The venous phase IC, Eff-Z, and λ_HU had higher diagnostic efficacy. Eff-Z had the best diagnostic performance at the venous phase. The AUC was 0.97. With 8.72 as the threshold, the differential sensitivity was 88.90% and the specificity was 94.70%. Conclusion: Quantitative analysis of multi-parameters of energy spectrum CT has certain diagnostic value for differentiation of esophagogastric junction cancer.

CT Differential Diagnosis of Intra-abdominal Aggressive Fibromatosis and Stromal Tumors

CHENG Qinghong, WANG Siwei, SHENG Mao

2019, 28(2): 255-262. doi: 10.15953/j.1004-4140.2019.28.02.12

Abstract(253) PDF(4)

Abstract:
Objective: Intra-abdominal aggressive fibromatosis and stromal tumors are easily confused in diagnosis, so comparative analysis the CT findings of both, to summary their key points of differential diagnosis. Methods: The difference of both in sites, cystic degeneration or necrosis, enhancement phase and enhancement degree were significant (P=0.01), it has high value for differential diagnosis, among them, enhancement phase and enhancement degree have important value. There was significant difference between both in the size, morphology and boundary of the lesion, as well as blood vessels, bleeding, gas and calcification in lesions, it has certain value for differential diagnosis. Conclusion: If the lesion is located outside the gastrointestinal, without cystic degeneration or necrosis, enhanced scan showed slight enhancement, and time-density curve showed slowly ascending linear type, we should consider intra-abdominal aggressive fibromatosis. If the lesion is located in the gastrointestinal wall, with cystic degeneration or necrosis, enhanced scan showed moderate to marked enhancement, and time-density curve showed parabola type, we should consider stromal tumors.

The Contrast-enhanced CT Diagnostic Value on Hepatic Sinusoidal Obstruction Syndrome

YAN Xuan, SUN Ying, KONG Ling, ZHANG Qijing, WEN Jing, SUN Xiaoli, WANG Rengui

2019, 28(2): 263-270. doi: 10.15953/j.1004-4140.2019.28.02.13

Abstract(326) PDF(4)

Abstract:
Objective: To evaluate the diagnostic value of contrast-enhanced CT in hepatic sinusoidal obstruction syndrome (HSOS). Materials and Methods: Six patients (2 males and 4 females) diagnosed with HSOS by clinical and imaging in our hospital were included in this study. All patients underwent contrast-enhanced CT examination. Observed the changes of liver parenchyma, liver related blood vessels and other images within the scanning range in contrast-enhanced CT imaging. The results of hepatic vascular ultrasound, angiography or contrast-enhanced MR were also referred. The characteristics of contrast-enhanced CT in HSOS were analyzed and summarized. Results: All 6 cases showed liver swelling and uneven decrease of liver parenchyma density in non-enhanced CT image. After enhancement, 6 cases displayed "patchy" or "geographic pattern" enhancement. In 1 case, there was also characteristic "radial shape" high density centered on the second hilum along the around of three hepatic veins. The three hepatic veins in 5 cases were not shown. In the other 1 case, the left hepatic vein was not shown, the middle and right hepatic vein became thin like a line. The hepatic segment of inferior vena cava was severely narrowed in 3 cases and slightly compressed in 3 cases. However, hepatic vascular ultrasound, angiography or contrast-enhanced MR examination confirmed that the venous blood flow in the hepatic vein and the inferior vena cava was smooth. Conclusion: Liver swelling and uneven decrease of liver parenchyma density in non-enhanced CT image and "patchy" or "geographic pattern" enhancement or characteristic "radial shape" high density centered on the second hilum along the around of three hepatic veins in contrast-enhanced CT, which contributes to the diagnosis of HSOS. However, contrast-enhanced CT has some limitations in the diagnosis of hepatic vein or inferior vena cava hepatic segment stenosis or occlusion.

Imaging Analysis of Malignant Bone Tumor in Scapula

LI Mingqiu, DU Gang, PENG Jiayou, HUANG Xueqiao, ZHANG Jiaxiong

2019, 28(2): 271-277. doi: 10.15953/j.1004-4140.2019.28.02.14

Abstract(274) PDF(3)

Abstract:
Objective: To summarize the types and imaging features of malignant bone tumors of scapula. Materials and methods: From April 2006 to December 2018, the preoperative X-ray and CT, MRI data of 18 cases of malignant scapular tumors confirmed by surgical pathology (male to female ratio: 14: 4, average age: 47 years old) were collected for retrospective analysis. Results: Metastatic tumors were more common in scapular malignant bone tumors (9/18, 50%), most of which were metastatic from lung adenocarcinoma. Ewing's sarcoma was also more common in this area (3/18), with small bone lesions with periosteal reaction and calcification, and large soft tissue masses are common manifestation. The second was solitary plasma cell tumor (2/18). Some of the lesions developed slowly and expanded, showing a low-grade malignant process. Magnetic resonance imaging (T2WI) and contrast-enhanced MRI are helpful to distinguish chondrosarcoma from osteosarcoma. In addition to osteosarcoma, Ewing's sarcoma, chondrosarcoma, epithelioid angioendothelioma should also be considered in the presence of radial periosteal reaction. Conclusion: Combined use of X-ray and CT, MRI can improve the preoperative diagnosis rate of scapular malignant tumor.

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2019 Vol. 28, No. 2