CT理论与应用研究

Comparison of Four Iterative Algorithm Based on Incomplete Projection Reconstruction

QUE Jie-min, WANG Yan-fang, SUN Cui-li, WEI Cun-feng, SHI Rong-jian, WEI Long

2012, 21(2): 169-178.

Abstract(1143) PDF(3)

Abstract:
In emission computerized tomography and transmission computerized tomography, the analytic algorithm reconstruction used incomplete data will result in image artifacts in the result reconstructed. But the iterative algorithm would improve the quality of reconstruction images. In this paper, four type iterative reconstruction algorithm is applied to experimental sparse projections and limited-angle projections of the resolution test phantom. Their advantage and disadvantages are analyzed quantitatively. The study will provide the reference for the clinical or engineering application of the algorithm.

A New Reconstruction Iterative Algorithm on Fan Beam CT

LIU Miao-ling, LIU Chang, QIU Jun

2012, 21(2): 179-185.

Abstract(972) PDF(0)

Abstract:
Computerized tomography model have parallel bean, fan beam and cone beam. Image reconstruction algorithms of fan beam most use image square partition. This paper gives a new image reconstruction discrete model, studies algebraic iterative correction methods and rearranging algorithm. The text discusses geometric significance based on this new model. The new algebraic iterative algorithms can improve the reconstruction quality and inspire new image reconstruction algorithm.

A Fast Algebraic Reconstruction Algorithm Based on Improved Projection Coefficient Computation

YANG Wen-liang, WEI Dong-bo

2012, 21(2): 187-195.

Abstract(1240) PDF(2)

Abstract:
Algebraic Reconstruction Technique is an important method for image reconstruction. To improve the reconstruction speed of ART, this paper presents a new and fast algorithm to calculate projection coefficient based on different situations of grids intercepted by ray. This Algorithm can calculate the projection coefficient by simple operation such as addition, subtraction and comparison. Since the computation of intersection and sorting in traditional algorithms are avoided, the reconstruction speed is greatly increased. The experiments using Shepp-Logan phanom show that the new algorithm is more effective than the traditional algorithms.

Visualization CT of Characteristics Formation and Stability of Foam of Porous Media

SHENG Qiang

2012, 21(2): 197-204.

Abstract(827) PDF(0)

Abstract:
Recently, the foam fluid is cared about by more and more academics in Enhance Oil Recovery (EOR). The CT technology has its own advantages in EOR mechanism. By researches and analyses foam flooding with BIR ACTIS (CT), this paper gives a visual description to the foam feature and distribution in media, uses a new visual method to study the oil saturation and reveals the mechanism of the foam flooding.Resultsof the study have significance for guiding the field application.

Improved Phase Shift and Phase Shift Interpolation Method Research

XUE Hua, ZHAO Xian-sheng

2012, 21(2): 205-212.

Abstract(779) PDF(0)

Abstract:
In order to realize the precise complex geological body shift position, using phase shift and phase shift interpolation method, the imaging quality and computation efficiency are two factors we must consider. Therefore in view of the actual encountered in the various problems, following are the technical improvement of phase shift and phase shift interpolation method: A discussion of the space in the domain of the dynamic boundary absorption; First put forward wave number domain filtering method, above two kinds of method effectively avoid the endpoint effect and making the calculation efficiency improved significantly. The method of small speed migration and phase shift factor analysis described, both proved significantly improve the migration profile of the imaging quality.

Thin Sand Thickness Predicting Technique Based on the Theory of Linear Transitional Medium

WEN Huan, XU Feng, ZHAO Ying-jie, CHENG Suo

2012, 21(2): 213-220.

Abstract(873) PDF(0)

Abstract:
It is one of the difficult problems in oil and gas exploration to predict the thin sand thickness. This paper introduces the linear transitional theory. Based on such theory, the linear transitional wedge model which is more closely to the practical medium is established. Following the forward modeling in time domain and the characteristic analysis of its response in frequent domain, a thought of thin sand thickness predicting based on turning frequency is proposed and a relevant working flow is also formed by the practical thin sand thickness prediction. Validated by the drilled-well data, it is found that the predicting results of the thin sand spatial boundary and thickness are coincide with the reality and that the method has a good future by widely using.

Logging Interpretation and Application Based on Three-water Model in Fractured Tight Sand Reservoirs

XU Xue-feng

2012, 21(2): 221-229.

Abstract(800) PDF(1)

Abstract:
The interpretation model of the fractured tight sandstone is basis of logging evaluation and quantitative calculation. According to the geological features of the fractured tight sandstone, the composition of the pore space is analyzed. Based on three-water conductive model for logging interpretation method, the conductive mechanism is discussed and derived, the three-water interpretation method for fractured formation is proposed, which can achieve a quantitative calculation of the saturation. In Longtan formation of Huangqiao area, the three-water components calculated is good agreement with NMR logging interpretation results, and the test results indicate that this model is applicable for logging evaluation of the fractured tight sandstone.

Orientation Correction Study for Horizontal Components in Marine Multi-component Seismic Exploration Based on Amplitude Method

LIU Yi-feng, FU Dan-dan

2012, 21(2): 231-238.

Abstract(799) PDF(0)

Abstract:
A new method of orientation correction for the horizontal-component in the situation of horizontal-component random orientated, called amplitude method, is put here, aimed at the most complicated situation in multi-component seismic exploration when the multi-component seismic data were acquired using the looped-draped seabed cable system. The satisfied results of orientation correction were obtained, via the testing of 3-D theoretical forward modeling data and the processing of 3-D multi-component seismic field data in this paper, that indicating the feasibility and practicality of the new method.

Basis Function Approach to Computerized Tomography

ZHANG Li, LIU Chang

2012, 21(2): 239-246.

Abstract(780) PDF(1)

Abstract:
We have a image reconstruction of the discrete model that based on the ideal small area replaces the original pixel grid in the traditional sense. The function about the distance form the ideal small area to the ray, to measure the size of the attenuation coefficient when the radiation passes through the ideal small area.In this image reconstruction of the discrete model we introduce the basis function.The discrete image is mapped into continuous image by convolution with a basis function.We discuss the conditions the basis function need to meet and give two basis functions and their firequency properties.

Ring Artifact Correction Method Based on Air Scan for Cone-beam CT

ZHANG Hua, HUANG Kui-dong, SHI Yi-kai, LI Ming-jun

2012, 21(2): 247-254.

Abstract(1145) PDF(6)

Abstract:
On the basis of analysis of flat panel detector correction methods and the residual causes of ring artifacts in cone-beam CT (CBCT), a simple correction method for CBCT ring artifacts based on air scan is proposed.Firstly, an air scan and measured object scan are performed using the same parameters in the same CBCT system.And then a series of slice images are reconstructed, respectively.Finally, the air slice images are subtracted from the corresponding slice images of the measured object to achieve the correction of the residual ring artifacts, at the same time playing a certain role in noise reduction.Experimental results demonstrate the feasibility and effectiveness of this method.

Reserching on Geometric Correction of Concrete CT Image

DING Wei-hua, LEI Man, GUO Rui

2012, 21(2): 255-261.

Abstract(791) PDF(0)

Abstract:
Meso-crack of concrete in CT image is the key object to study.It’s very difficult to observe directly meso-crack of concrete in CT image based on grey scale conception.Image enhancement processing method is needed to CT image according to subtraction conception.Subtraction CT image has some shadow-positive circle phenomenon.So before subtraction operation, CT image is needed to correct.Correction methods including whole translation, whole geometric and region of interest correction method, while region of interest correction method is objective.This paper proposes a new useful method to gain meso-crack information of concrete in CT image.

The Features of Traumatic Intrahepatic Biloma on CT and MRI

DING Zhang-qing, LI Jun, SUN Ying-ying

2012, 21(2): 263-267.

Abstract(1001) PDF(0)

Abstract:
Objective:To investigate the features of traumatic intrahepatic biloma on CT and MRI.Methods:The imaging data of 10 patients with traumatic intrahepatic biloma clinically confirmed were analyzed retrospectively. Results:All patients underwent CT examination,2 cases underwent MRI examination in the course of the disease. All with hepatic parenchymal laceration,a short period of trauma,it showed low-density or large sheet long T1, long T2 signal intensity,follow-up soon showed water density or signal intensity in liver on CT and MRI.7 cases were single cystic,multiple in 3 cases.Multiple biloma along the biliary tree were pouch pocket arrangement. Except for 7 cases were naturally smaller,the remaining 3 cases were cured by surgery or ultrasound or CT-guided drainage,and whose contents were bile components.Conclusion:It has crucial significance for the diagnosis and treatment to recognize the CT and MRI features of traumatic intrahepatic biloma.

The Imaging and Pathological Analysis of Extranodal Lymphoma in Head and Neck

ZHANG Jian-xin, YANG Xiao-tang, WANG Yan-yan, CHEN Mai-lin, WANG Jun

2012, 21(2): 269-276.

Abstract(785) PDF(1)

Abstract:
Objective:To explore the imaging and clinical features of extranodal lymphoma in head and neck. Methods:51 extranodal lymphoma patients in head and neck were confirmed by surgery and pathology.The CT and MR images data were analyzed in comparison with surgical and pathological results.Diagnostic value of the CT and MR imaging were analyzed.Results:All 51 cases were non-Hodgkin lymphoma(NHL).Among all cases B-cell lymphomas accounted for 62.75%(32 cases).19 cases were T-cell lymphoma(37.25%).The most common site of extranodal lymphomas located in nasal cavity and pharynx ring.23 cases in nasal cavity(45.10%), 20 cases in pharynx ring(39.22%),The rest part 8 cases(15.69%),include:3 cases in orbit,2 cases in laryngeal, 2 cases in thyroid and 1 case in parotid.The lymph nodes metastases were observed in 18 cases.According tumor form all lymphoma were divided into three types:31 cases single mass type(60.78%),17 cases diffuse swelling type(33.33%),2 ulcer or necrotic type(5.89%).Conclusion:CT and MR images showed the special characteristics of head and neck extranodal lymphoma.Combined with clinical characteristics the imaging examinations could indicate the location,morphology,surrounding tissue and lymph nodes metastases and have great value in clinical diagnosis,staging and treatment.

The Application Value of Susceptibility Weighted Imaging in Patients with Early Intracerebral Hemorrhage and Hemorrhagic infarction

XU Peng-jun, JIANG Qing-jun, LI Jie, ZHU Ming, YU Bing-bing, YANG Xiao

2012, 21(2): 277-282.

Abstract(838) PDF(0)

Abstract:
Objective:To evaluate the application value of susceptibility weighted imaging (SWI) at 1.5 Tesla (t) MRI in patients with hyper acute intracerebral hemorrhage (ICH) and hemorrhagic infarction (HI).Method: Collected twenty-five patients (average age:58) with hyper acute ICH and twenty-two patients (average age:54) with acute HI from 2010.2 to 2011.11.All cases underwent T1WI, T2WI, FLAIR, DWI and SWI scan with 1.5t MRI scanner (GE Signa 1.5T EXCITE HDMR).ICH times of accident are in 6 hour, HI times of accident are in 24 hour.Results:The display rate of intracerebral hematomas was 80% (20/25 cases) in T2WI, but was 100% (25/25cases) in SWI.All cases showed the scope of bleeding greater in SWI than conventional sequence.The display rate of hemorrhagic infarction was 9% (2/22cases) in T1WI, but was 100% (22/22 cases) in SWI. Conclusion:The SWI sequence has greater help in the diagnosis of early stroke type and hemorrhagic infarction than conventional MR sequences.SWI has great guide significance for clinician treatment.

Diagnostic Value of ¹⁸F-FDG PET/CT for Gynecological Malignancies

DENG Kai, DONG Gui-qing, ZHANG Cheng-qi, WANG Guang-li, LIU Qing-wei, SONG Ji-qing

2012, 21(2): 283-289.

Abstract(681) PDF(0)

Abstract:
Objective:To investigate the diagnostic value of ¹⁸F-FDG PET/CT in pre-operative diagnosis and post-operative follow-up of gynecological malignancies.Materials and Methods:33 patients(17 patients who were doubted malignant tumors and 16 patients who were suspected recurrence or metastasis after operation)were scanned by ¹⁸F-FDG PET/CT.The results were compared with the conventional imaging modalities.Results:In 17 patients who were doubted malignant tumors,the patients-based diagnostic ability of PET/CT was similar with conventional imaging modalities.For metastasis diagnosis,the sensibility,specificity,accuracy,positive predictive value and negative predictive value of the two methods were 85.7% vs 28.6%,100% vs 100%,94.1% vs 70.6%, 100% vs 100%,90.9% vs 66.7%.The sensibility of the two methods had significant difference.And the lesion-based accuracy of PET/CT for metastasis was also significantly higher.In 16 patients who were suspected recurrence or metastasis after operation,The lesion-based sensibility,specificity,accuracy,positive predictive value and negative predictive value of the two methods were 76.9% vs 48.7%,77.8% vs 66.7%,77.1% vs 52.1%, 93.8% vs 86.4%,43.8% vs 23.1%.The sensibility and accuracy of PET/CT were higher than that of conventional imaging modalities significantly.Conclusion: ¹⁸F-FDG PET/CT,as a non-invasive imaging modality,has considerable value in pre-operative diagnosis and post-operative follow-up of of gynecological malignancies.

The Value of 64-slice Spiral CT Angiography in Diagnosing Aortic Dissection

ZHUANG Gao-ming, YE Hai-ming, LIN Bo-miao, YE Qiang

2012, 21(2): 291-296.

Abstract(724) PDF(0)

Abstract:
Objective:To investigate the value of 64-slice spiral CT angiography in diagnosing aortic dissection. Methods:Retrospective analysis 10 cases of aortic dissection in 2009 to 2011 first half,all diagnose by 64-slice spiral CT angiography,and 6 cases Treatment by DSA.Results:CT results,6 cases were classified with Stanford type B,and 4 cases with Stanford type A.Six cases of Stanford B type treated by aortic endovascular repair of stent-graft.Postoperative classification are full compliance with CT.Four cases of Stanford type A are considered by Clinical unsuitable for Interventional procedures,conservative treatment,no surgical.Conclusion:The 64-slice spiral CT angiography not only a good diagnosis method of aortic dissection,but also can type correctly,guide treatment.

CT Findings and Cause Analysis of Tuberculosis Nodules or Masses Misdiagnosed as Lung Cancer

CHEN Yin-yin, CHEN Wei-tang, CHEN Ying-feng

2012, 21(2): 297-303.

Abstract(958) PDF(0)

Abstract:
Objective:To investigate CT findings of tuberculosis nodules or masses misdiagnosed as lung cancer and analyze their causes.Methods:40 patients with tuberculosis lesions≥1cm in diameter were misdiagnosed as lung cancer on CT.The shape,internal features,enhanced features,margin,adjacent lymph nodes and lung tissue changes were analyzed retrospectively.The causes of misdiagnosis were also analyzed.Results:(1)The shape and location of the lesion:oval in 22 cases,lobulated in 10 cases,irregular in 8 cases.18 cases in upper lobe,12 cases in lower lobe,10 cases in middle lobe.(2)Internal features:inhomogeneous density in 28 cases,cavitation in 3 cases,calcification in 7 cases,cavitations with calcification in 2 cases.(3)Lesion enhancement characteristics: moderate inhomogeneous enhancement in 18 cases,moderate homogeneous enhancement in 5 cases,slightly inhomogeneous enhancement in 6 cases,no enhancement in 11 cases.(4)Marginal features and adjacent tissue changes:irregular margin in 40 cases,12 cases of ill-defined margin,spicule sign in 18 cases,satellite lesions in 40 cases,pleural thickening and adhesions in 11 cases,pleural indentation in 3 cases,drainage of the bronchial wall by thickness in 5 cases.(5)Hilar and mediastinal lymph nodes:Lymph nodes enlargement in 31 cases. Lymph nodes homogeneous enhancement in 21 cases,ring enhancement in 4 cases,no enhancement in 6 cases. Conclusion:CT findings of tuberculosis nodules or masses misdiagnosed as lung cancer were not typical.Nodules or masses with satellite lesions may be suggestive of tuberculosis,but biopsy to confirm the diagnosis was necessary.

Pitch Optimizing Combination of Thoracic and Abdominal CTA Image Quality and Radiation Dose Discussion

ZHANG Hai-bo, FU Chuan-ming, CHEN Lun-gang, XU Lin, WANG Kai-hua

2012, 21(2): 305-311.

Abstract(952) PDF(1)

Abstract:
Objective:To evaluate the pitch of the thoracic and abdominal MSCT CTA image quality,and compare the radiation dose.Materials and Methods:Collection of clinical suspected thoracic and abdominal vascular lesions in 90 patients,according to the different pitch were randomly divided into 3 groups(n=30),group A:a pitch of 1.375:1,55 mm/s bed velocity;group B:a pitch of 0.984:1,39.37 mm/s bed velocity;group C:pitch,0. 516:1 bed velocity 20.62 mm/s,using the same injection rate and dose of contrast contrast tracking trigger scanning.After obtaining data from imaging director and supervisor technician in a AW4.4 workstation for image quality evaluation.Results:Through the pitch after optimization,A,B,C 3 groups average each patient scan time respectively:(12.60±0.54)s,(17.40±0.44)s,(33.10±1.48)s,DLP respectively:(1 462.50±71.56)mGy.cm, (2 010.55±62.14)mGy.cm,(3 821.58±198.50 the difference between mGy.cm),which was statistically significant(P<0.01);3 groups of effective dose(ED)were:24.96 mSv,34.18 mSv,64.97 mSv,A group than in B group for each ED9.22 reduction in patients with mSv,reduced by 26.97%(9.22/34.18),A group than in C group for each patients 40.01 ED by mSv,was significantly reduced by 61.58%(40.01/64.97).3 groups in the ascending aorta,abdominal aorta,renal hilar level of bilateral external iliac artery end average CT values were:353.00 Hu, 350.77 Hu,350.70 Hu,the difference between the 3 groups was not statistically significant(P>0.05), recombinant vascular definition and display of vascular branching number also no difference.Conclusion:The groups A pitch optimization,fast bed velocity scanning parameters can significantly reduce the patient radiation dose,so as to ensure the image quality and meet the requirements of diagnosis.

Magnetic Resonance Imanging Diagnosis of Limbs Lymphangioma

JIANG Li-hua, CHEN Xiao-bo, YUE Yun-long, ZHAO Li-jun, DUAN Yong-li, FU Yan

2012, 21(2): 313-319.

Abstract(904) PDF(0)

Abstract:
Objective:To evaluate the MRI findings of cavernous lymphangioma in lower limbs,in order to improve the diagnosis and differential diagnosis of this disease.Materials and Methods:10 cases with histologically confirmed carvnous lymphangioma were collected and retrospectively studied.MR scan were performed in all cases,and CT scan in 2 cases.Results:The typical image shows the hyperplasia soft tissues of lower extremity as grids,with the impractical and broden lymphatic vessels.The extent of disease usually extensive,it can involve musculus and ossature.Conclusion:MR examination is very useful in diagnosing the carvous lymphangioma,It can help determining the extent of disease,and wether the musculus and ossature were involved or not.It was very useful to determine the opration.

Correlation Analysis between Low Body Mass Index and Image Quality Using PGA CT Technique

ZHAO Lei, WANG Ze-feng, LIU Ai-shi

2012, 21(2): 321-327.

Abstract(884) PDF(0)

Abstract:
Objective:To evaluate the relationship between body mass index(BMI)and image quality for fixed tube current and tube voltage.Methods:Forty patients with average body mass index(BMI)20.12 kg/m²,average age 53.16 years were included in this study,using PGA scan technique(tube voltage was 120 kV and tube current was 400 mA).All patients were evaluated for mean attenuation,noise,signal-to-noise ratio(SNR)in aortic root. To evaluate the relationship between body mass index(BMI)and image quality using Pearson correlation analysis. AP value below 0.05 was considered to be statistically significant.Results:The BMI was statistically significant influence on noise,signal-to-noise ratio(P=0.000).The BMI was no statistically significant influence on the mean attenuation(P=0.314).Conclusion:The use of low BMI adapted mA selection method can obtain consistent image quality in abstracto and may reduced effective dose.

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2012 Vol. 21, No. 2