CT理论与应用研究

Local Reconstruction Algorithm Based on the Special Filter and Its Analysis

SONG Pei-ran, QU Gang-rong

2009, 18(3): 1-9.

Abstract(699)

Abstract:
In order to reduce the harm of X-ray on human body,local reconstruction is becoming one of the important studies in image reconstruction.The local reconstruction algorithm based on the special filter is studied.Reconstructing the local image by using the projection data through the region of interest(ROI),generates the unknown constant bias in the reconstructed image in general.By making continuation along the radial direction,the unknown projections are derived from the projections in the ROI.And by reconstructing from the modified projection,the local reconstructed image is improved.The error analysis of this method based on the special filter is derived and this algorithm is implemented in fan beam reconstruction.According to the numerical experiment,the conclusion is obtained that this algorithm is also available to fan beam reconstruction problem.

Restricted Landweber Iteration Algorithm for Image Reconstruction from Projection

LI Hong-yan, TONG Li-li

2009, 18(3): 10-14.

Abstract(541)

Abstract:
Image reconstruction from incomplete projections is a key problem in image reconstruction. In this paper, based on least-square optimization, some unknown error are adopted as inequality constraints. A new restricted iterative algorithm using Landweber iteration is proposed for the ill-posed problem. Compared with non-restricted iterative algorithm, under the condition of same computation time, this algorithm is more stable, and can give less error and higher fitness image. The effectiveness of the algorithm has been verified by image reconstruction using parallel-scanning data. The quality of reconstructed images clearly indicates the superiority of the proposed algorithm.

The Research and Realization of a Re-Sorting Algorithm Used in Fan-Beam CT Short-Scan Reconstruction

MA Chen-xin, YAN Bin, JIANG Hua

2009, 18(3): 15-21.

Abstract(783)

Abstract:
This paper reviews two main categories of reconstruction algorithms in parallel CT and fan-beam CT,and introduces the approachs to implement them on PC.In order to speed up CT scan and reconstruction,based on the analysis of the beam geometries relationship between parallel scan and fan-beam scan,the paper introduces a special scan model named short-scan which differ from traditional full-scan,and proposes an approach named parallel re-sorting to reconstructing images from short-scan fan-beam data.And then realizes it.According to experimental results,we find that reconstruction speed is improved remarkably.

The Application of Sparse Signal Recovery Theory in CT Image Reconstruction

WANG Lin-yuan, LI Lei, YAN Bin, JIANG Cheng-shun, WANG Hao-yu, BAO Shang-lian

2009, 18(3): 22-29.

Abstract(626)

Abstract:
The new image reconstruction algorithm remains one of the hot problems in the current research of computed tomography(CT),among which the reconstruction algorithm with limited views is a difficult problem in practice.Recently,a sparse signal recovery theory was proposed by Terence Tao and his colleagues,which may give a strategy for solving this problem.We introduced this theory and presented some primary simulated results in this paper.The realization of the strategy is significant in some special applications for cone beam CT imaging,which will be a new direction in this field and will greatly influence on this field.

Application of Cone Beam Computed Tomography Technology in Oral Clinical Practice

HU Hai-feng, ZHANG Li, CHEN Zhi-qiang, LI Liang, WU Hong-xin, LI Ying-cao

2009, 18(3): 30-37.

Abstract(618)

Abstract:
The application of Cone Beam Computed Tomography(CBCT) in three-dimensional oral imaging has recently become a focus for both CT technology researchers and dentists.In particular,with the development of dental implanting technology,the CBCT image based implant planning and surgery-guide template design has become a new research field.This paper provides a summary of the general principle of dental CBCT imaging and an overview of its clinical applications.We compared dental CBCT and conventional CT,and concluded some key techniques and research spots to be used for reference by researchers in this field.

Beamlet Pre-Stack Depth Migration Based on Gabor Frame Theory

ZHANG En-jia, WANG Xi-chong, LIANG Dong, TANG Xiao-biao

2009, 18(3): 38-45.

Abstract(587)

Abstract:
Base on beamlet's local dualism in both wavefield decomposition and space propagation, use the Fourier propagate operator to complete the propagation of the beamlet, combine the imaging conditions to gain the imaging value and then imaging.To testify the theory, first construct beamlet and the beam source record, then apply it to pre-stack depth migration numerical experimentation, the outcome is inspiring. It also testified that the beamlet pre-stack migration is both effective and efficient.

The Application of Geoelectricity CT in Cave Exploration in Hotspring of Tangquanchi-Shangcheng Henan

WANG Ji-hua, LI Qing-lin, XIE Ru-yi, XU Shun-qiang

2009, 18(3): 46-51.

Abstract(564)

Abstract:
The resistivity CT in the geothermal investigation,may objective,earnest reflect the fault,the hot geologic body essential feature on the spot.This article elaborated the resistivity CT's principle,the method as well as the Tangquanchi hot spring geothermal geological condition,has carried on the interpretation and the generalized analysis to four resistivity CT section plane,to decide the well to provide the basis.

Ultrasonic Testing of the Cast-in-Place Bored Pile

YIN Jian-wu, LI Qing-lin

2009, 18(3): 52-59.

Abstract(572)

Abstract:
Combined with the ultrasonic testing of the cast-in-place bored pile in jiaozheng Highway,the paper introduces and analyzes not only the application steps of ultrasonic transmission but the judgment of defect in pile.By the example prove that ultrasonic transmission can judge the location and the range of defect exactly and evaluation of the degree of defect.It is a good way to inspect the quality of cast-in-place piles.

Experiment Study on Micron Crystal Defect of Explosive Based on μVCT

ZHANG Wei-bin, DAI Bin, TIAN Yong, HUANG Hui, YANG Cun-feng, ZONG He-hou, LI Hong-zhen

2009, 18(3): 60-65.

Abstract(557)

Abstract:
The inner defect of explosive crystal is one of the key factors that affect the performance of explosive material.The structure of typical crystal explosive(HMX) is studied with microfocus x-ray industrial volume CT(μVCT) and the micro hole ratio is quantificationally analyzed in this paper.The results indicate that micron holes are extensively presented in HMX crystal and the micro hole ratio is up to 1%~2%,which reveal initial damage existence in explosive parts and the difference between theoretical density and actual density of crystal.The micro hole of HMX crystal may reduce effectively and density and performance are improved after a certain technical treat.The inner structure and micro hole ratio measurement can be effectively studied with μVCT for HMX crystal over tens of micron.This research provides an intuitionistic reliable experimental means for studying molding performance and damage destruction mechanism of explosive parts.

Applications of Industrial CT in Reinforced Rigid Polyurethane Foam Non-destructive Testing

YANG Cun-feng, LI Jing-ming, TIAN Yong, ZHANG Wei-bin, DAI Bin

2009, 18(3): 66-71.

Abstract(516)

Abstract:
The rigid polyurethane foam with high mechanical properties, as structure materials, can be obtained by filling reinforcing materials. Structure characteristic and material composition influence mechanical properties of RRPUF. In this thesis, 3D structure of glass fiber RRPUF was tested by microfocus cone-beam X-ray industrial computed tomography. Structure characteristic such as shape, position, size and volume percentage of glass fiber and porosity defect inside glass fiber RRPUF was analyzed by CT analysis software. It shows that microfocus cone-beam X-ray industrial computed tomography is important method in non-destructive testing for RRPUF structure characteristic.

Application of Large Industrial Computed Tomography in Nondestructive Testing of Key Components of Railway Vehicles

XIAO Yong-shun, HU Hai-feng, CHEN Zhi-qiang, ZHANG Li, YANG Guang, YONG Tao

2009, 18(3): 72-78.

Abstract(582)

Abstract:
Swing bolster and side frame,as important components of train bogies,play a crucial role in train movement.The requirements of high-penetration testing facilities for manufacturers to inspect a large number of workpieces are very strong.This paper introduced the large industrial CT system for the non-destructive inspection of the key components of the railway vehicles,elaborated the system design and the scanning flow,Through an example,we demonstrated the non-destructive testing application of industrial CT in imaging a swing bolster and a side frame.The successful practical applications show the industrial CT can be used in the detection of internal structure and defects of swing bolsters and side frames,such as internal air holes,sand and slag inclusions,porosity,shrinkage,cold shut and casting cracks and etc.The performance can meet the requirement of this industry well.

Optimization of a 3D FLASH Water Excitation MRI Sequence for the Visualization of Articular Cartilage

FANG Ting-song, PENG Jia-you, ZHAO Xiao-mei, QIN Hong-wei

2009, 18(3): 79-84.

Abstract(580)

Abstract:
Objective To optimize a rapid cartilage dedicated 3D-FLASH sequence using water excitation instead of conventional spectral fat suppression and compare the value of 3D-WE-FLASH sequence with 3D-FS-FLASH on evaluating articular hyaline cartilage of knee in 10 healthy volunteers.Methods.The knees of ten volunteers were scanned at 1.5T by using sagittal 3D-WE-FLASH and 3D-FS-FLASH,and different repetition time(TR),echo time(TE),or flip angle(FA) were adoped in 3D-WE-FLASH sequence.The signal noise ratio of cartilage was calculated.Then the contrast noise ratio between cartilage and its surrounding tissues,and contrast noise ratio efficiency between cartilage and fluid were calculated to quantitatively analyze the various sequences.Quantitative results were evaluated with repeated measures ANOVA. Results Group 4 had a significantly higher SNR_ca,CNR_ca-fluid,CNR_ca-bone,CNR_ca-fat,CNR_ca-menisus than in the group 1,2,3.Group 2 had a significantly higher SNR_ca,CNR_ca-fluid,CNR_ca-fat,CNR_ca-bone than group 1,3.Group 4 had a significantly higher CNR_ca-fluid eff than group 1,3,and there is no differert with CNR_ca-fluid eff between group2,4. Conclusion 3D-WE-FLASH sequence which had been optimized is valid for short acquisition time and hyaline cartilage visualization.

Application of the Spiral CT Scan with MPR Reconstruction in the Degenerative Lumbar Spinal Stenosis Clinical Diagnosis

HU Shao-ping, SONG Huai, ZHOU Li-qiang

2009, 18(3): 85-90.

Abstract(537)

Abstract:
Objective: To investigate the performance of spiral CT scan and its clinical significance for the degenerative lumbar spinal stenosis diagnosis.Methods: The CT scan data from190 patients with the clinical symptoms of degenerative lumbar spinal stenosis were retrospectively analyzed.Results: CT scan showed that bulging disc/prominent fate postal vertebroplasty,vertebral spondylolisthesis and facet hypertrophy,ligamentum flavum hypertrophy,ossification of posterior longitudinal ligament to the central spinal canal sagittal diameter and smaller transverse Drive,lateral recess,foraminal narrower manifestations are the major changes in the degenerative spinal stenosis.We found that 19 cases with typeⅠ,central spinal stenosis;97 cases with typeⅡof spinal nerve root canal stenosis,lateral spinal stenosis;74 cases with typeⅢor mixed type(Ⅰ,Ⅱ-type) among the 190 patients.Spinal stenosis mainly happened at the L4-L5 and L5-S1.Conclusion: Spiral CT scan combined with the MPR reconstruction of interesting regions is highly sensitive to the discovery,evaluation and diagnosis of degenerative spinal.

64-MSCT Coronary Angiography with Reduction Radiation Dose

CHENG Ying, GUAN Ji-tian, JIN Yang, GUO Yue-lin, ZHANG Yuan-fang

2009, 18(3): 91-95.

Abstract(624)

Abstract:
Objective: To optimize the scan protocol,and reduce the radiation dose in coronary angiography with 64-MSCT.Methods: 60 patients were randomly divided into two groups,30 included in each group.Calcium score images were scanned by tube current of 430 mA and 80 mA;delayed time was detected by timing bolus and Smart Prep,respectively;Coronary angiography was performed using ECG-gated protocol without tube current modulation and that with tube current modulation.In all groups,the mean effective dose and signal noise of ratio were calculated and compared.Results: Mean ED of calcium score scan obviously decreased from 2.35 ±0.42 of 430 mA to 0.42 ±0.03 of 80 mA;that of the delayed time detection reduce increasingly from 1.39 ±0.14 by timing bolus to 0.13 ±0.04 by Smart Prep;and that of coronary angiography protocol reduced from 28.22 ±4.90 without tube current modulation to 21.14 ±1.54 with tube current modulation.There were significant differences between mean SNR by 430 mA with that by 80 mA in calcium score scans,but there were no significant differences between mean SNR without tube current modulation with that with tube current modulation.Conclusion: Using the scan protocol with tube current of 80 mA in calcium score,delayed time detection of Smart Prep,and ECG-gated tube current modulation,the radiation dose of coronary angiography with 64 MSCT could be reduced increasingly,and image quality achieves the diagnostic desire.

64-Slice Spiral CT Angiography in the Head and Neck Vascular Lesions of Clinical Application

ZHANG Su-yan, SANG Ya-rong, LI Wei-min

2009, 18(3): 96-101.

Abstract(543)

Abstract:
Objective: To investigate the 64-slice CTA in the head and neck in the diagnosis of blood vessels.Methods: Cases of head and neck vascular CTA200 using maximum intensity projection MIP,volume rendering VRT,MPR and MPR software Inspace subtraction three-dimensional reconstruction techniques,multi-angle observations,of which 92 cases have MR,DSA and surgical information using double-blind comparison of various video effects,summed up the advantages and disadvantages of 64-slice CTA.Results: The 64-slice CTA less medication,small doses of radiation,scanning and imaging speed,image clarity,three-dimensional sense,the direction of rotation can be observed.VRT and MIP is the most commonly used method,Inspace Subtraction software can display the picture of the head and neck blood vessels.Conclusion: The 64-slice CTA can be used as head and neck vascular lesions of conventional screening methods can be widely used.

Diagnosis of Esophageal Cancer by X-ray Barium Meal and CT Scan

YU Hong-sheng, JI Liu-zhou

2009, 18(3): 102-109.

Abstract(579)

Abstract:
Objective: To analyze the X-ray barium meal and CT scan in the diagnosis of esophageal cancer imaging features,as well as the advantages and disadvantages and the diagnostic value of esophageal cancer,to raise imaging technology to improve the diagnosis of disease.Methods: Retrospective analysis of imaging data of 56 cases confirmed by surgery or pathology of the esophagus,all cases were carried out X-ray barium meal and CT examination,imaging data integrity.Results: a) The distribution: 56 cases,eight cases in cervical esophagus,10 cases in the upper chest,23 cases in chest paragraph,15 cases in thoracic segment.b) X-ray barium meal Signs: Early performance showed mucosal thickening,disorders,weakened peristalsis,as well as a small filling defect and small Shadow(13 cases);in mi8ddle and late period shows mucosal destruction,luminal stenosis,wall stiffness,as well as larger filling defect and malignant Shadow(43 cases).c) CT signs: Direct signs for irregular wall thickening(56 cases),intracavitary mass(36 cases),luminal stenosis(51 cases) or occlusion(3 cases),the upper expansion of the narrow(43 cases);indirect signs showed the tumor is close and transfer to the structure of the violations,as well as signs of complications.showed violations of fat lines around the esophagus(43 cases),tracheal bronchial violations(16 cases),aortic violations(22 cases,of which three cases were suspicious),pericardial violations(7 cases),lymph node metastasis(8 cases),complicated by lung abscess(1 case).d) Compare with operation pathonology diagnosed: X-ray barium meal correct diagnosed rate was 83.8%,CT scan correct diagnosed rate was 95.3% both combined diagnosed correct rate was 100%.e) CT staging: Ⅱ period were 13 cases,Ⅲ period were 36 cases,Ⅳ period were 7 cases.Conclusion: X-ray barium meal and CT scan each with their advantages and disadvantages.X-ray barium meal can observe the change in the function of esophagus,mucosal lesion and length showed precision,CT scan showed advantages in the tumor location,size,scope and invaded the surrounding tissues and lymph node metastasis.The combined use in favor of a comprehensive observation of the scope and extent of the lesion of esophageal cancer,to improved the diagnostic accuracy of imaging,there were active role inguide clinical stage and to determine program of treatment and surgery and prognosis.

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2009 Vol. 18, No. 3