CT理论与应用研究

Application Progress of Adaptive Statistical Iterative Reconstruction in Reducing Radiation Dose

FANG Lin, LI Liang

2013, 22(2): 207-213.

Abstract(546) PDF(5)

Abstract:
As a new CT reconstruction algorithm,adaptive statistical iterative reconstruction(ASIR),could not only reduce radiation dose at body CT,but also provide imaging examples in comparison with low-dose and standard-dose filtered back projection CT.The ASIR reconstruction algorithm is a promising technique for providing diagnostic quality CT images at significantly reduced radiation doses.The development and application of ASIR were reviewed in this article.

The Comparative Study of Equiangular Fan-beam CT and Equidistant Fan-beam CT

ZHANG Cong-zhe, LI Xiao-wei, YANG Kun

2013, 22(2): 215-223.

Abstract(609) PDF(3)

Abstract:
Fan-beam CT can be divided into equiangular CT and equidistant CT.For the detector unit arranged in different ways,there are some differences in data acquisition and reconstruction,which resulting in different reconstruction results.An introduction to the two kind of fan-beam CT based on filter back projection reconstruction algorithm.Using Shepp-Logan phantom to simulate and compare the reconstruction image.

The Splitting Parameters Computation in the Presence of Multiple Anisotropy Layers

LI Zhen, WU Ping-ping

2013, 22(2): 225-236.

Abstract(596) PDF(1)

Abstract:
It has long been recognized that the presence of complex anisotropy will result in variations in apparent splitting parameters with incoming polarization azimuth,and this will open doors for new work on imaging complex anisotropy structure at depth.In this study,we calculate the apparent parameters(φ,δt) variations as a function of incoming polarization with π/2 based on multiple layers.Compared with the result of SplitLab software,we find that the result calculated in our program is in good agreement with SplitLab on two-layer model,which strongly support our program.In three-layer model,we change the order of the layers and calculate the apparent splitting parameters for each model.We find that the order of the layers strongly effects the apparent splitting parameters(φ,δt),but the period is consistent π/2.Finally,we show real data to display the properties of three-layer;which may help to understand the process of imaging complex anisotropy structure at depth.

The Image Reconstruction Iterative Algorithm Based on Calculating Points with Fractal Corrector

LIU Chang, YANG Xiao-ling, QIU Jun

2013, 22(2): 237-243.

Abstract(566) PDF(4)

Abstract:
We introduce fractal corrector in the iterative algorithm for image reconstruction based on calculating points discrete model.The projection line is surrounded by a self-similar string formed by the Hilbert curve units.The Hilbert curve unit’s attenuation weight to projection has clear geometrical meaning as well as physical meaning.The line integral of projection is approximated accurately by compacting the calculating points.The Hilbert curve unit is an effective corrector in improving the algorithm since the uniform templates are formed by the self-similarity of fractal structure.In addition,the symmetry of the model could be used to accelerate the computing speed as well as to improve the imaging precision.

Affect of CT Scanning Parameters to the Quality of Rock and Soil Tomograms

CHEN Shi-jie, ZHAO Shu-ping, XING Li-li, ZHENG Jian-feng, DU Yu-xia

2013, 22(2): 245-254.

Abstract(580) PDF(2)

Abstract:
This paper designs a set of experiments to choose four different soil samples and studies the specific CT scanning parameters,which impact on the quality of rock and soil samples tomograms by use of direct method and indirect method and combining with the CT number changes.The parameters include the scanning voltage,the collimation mode,the filtering function,the samples size et al.The results showed that the scanning voltage and the filtering function have a great impact on rock and soil samples tomograms and CT numbers;the collimation mode and reconstruction matrix has little effect on the experiment results;The tomograms enhancement or inhibition depend on the chosen filter function properties,and have nothing to do with the soil.The following work provides the optimal principle of CT scanning parameters to improve the quality of rock and soil tomograms and obtain a relatively optimal CT numbers of rock and soil by means of the reasonable scanning parameters.

Q Value Tomography in Laterally Inhomogeneous Media: Method, Software and its Application

FAN Ji-chang, WANG Fu-yun, LIU Ming-jun, HAI Yan

2013, 22(2): 255-264.

Abstract(514) PDF(2)

Abstract:
Q value structure of the crust has great significance for understanding of non-elastic nature of crustal structure,thermal activity,crustal inhomogeneity,and fault distribution.Based on absorption characteristic time t^{*^{the GUI software for two-dimensional Q tomography has been written in this paper.Amplitude spectra of deep seismic sounding data can be calculated quickly and easily.The absorption characteristic time reflecting seismic wave attenuation can be obtained through fitting the amplitude spectra,and two-dimensional Q structure can be obtained by two-dimensional Q tomography using t^{*^{data.The real example shows that the method and the software are effective and feasible.}}}}

Experiment and Application on Detecting Geological Conditions of Mine Workface by Seismic Wave CT Technology

CHENG Gang, ZHANG Ping-song, WU Teng-fei, ZHANG Cheng-qian, YANG Fa

2013, 22(2): 265-273.

Abstract(518) PDF(2)

Abstract:
There are many geological factors that affect the safety production in coal seam workface.The geological anomalies characteristic can be explained according to the velocity distribution of coal seam revealed by the tomography techniques.By building working face test model,using model tests to establish the system contents such as CT detection technology methods of seismic waves,observing system layout,data acquisition parameters,data processing and geological interpretation.The practical results of the site exploration project shows that the CT imaging accuracy and resolution of the seismic waves can meet the on-site production and technical requirements.And the geological anomalies body in the mine workface can be tested and distinguished effectively.

The Application of the Well between Resistivity CT Method to the Engineering Testing

TANG Ying-jie, GE Wei-zhong

2013, 22(2): 275-282.

Abstract(507) PDF(2)

Abstract:
As a result of the terrain and type of device,the method of ground high density resistivity cant reflect the geology accurately.This paper mainly introduces the working method of the well between resistivity CT.In view of the practical work,we carried out the numerical simulation test and forward-inversion calculation,and applied the method while detecting deep karst and the effect of the deep curtain grouting.We summarized the attention in the process of data acquisition and got the result and the drilling data for a comparative analysis and achieved a better result.

The Denoising Method Based on Non-local Means for Sequence of Slice Images in Cone-beam CT

LI Xiang-xin, BU Kun, HUANG Kui-dong, ZHANG Ding-hua, ZHENG Jia

2013, 22(2): 283-290.

Abstract(569) PDF(3)

Abstract:
A denoising method based on Non-local means for sequence of slice images in cone-beam CT is proposed, according to the properties of the noise and sequence of slice images of cone-beam CT system, moreover, the definition of filtering degree is proposed as well. The relation of filtering strength to standard deviation of the background zone before filtering and the structure zone of method noise images is established. Moreover, the relationship between filtering strength and the standard deviation of the background zone before filtering is established under the same filtering degree to compute the filtering strength of each slice image, which contributes to the consistency of filtering degree of all slice images. The efficiency and feasibility of this method is verified by the experiment.

An Adaptive Enhance Method Based on Unsharp Masking for Cone Beam CT Images

ZHENG Jia, ZHANG Ding-hua, HUANG Kui-dong, LI Xiang-xin

2013, 22(2): 291-296.

Abstract(553) PDF(5)

Abstract:
An Unsharp Masking based enhance method using Laplacian for sequence of CT images is proposed. In this method, local variance of each pixel is computed, according to which and the two gradient thresholds the image is divided into three regions. Different region is given different enhance coefficient, which is determined by it's local variance, and a Laplace template which is determined by corresponding gradient of current pixel. Thus, the adaptive and anisotropic enhancement of image is achieved. The results show, the enhanced images using proposed method have higher SNR, lower MSE and clearer details comparing which the traditional ones. The proposed method performs well in the enhancement of sequence of cone-beam CT images.

Base on Improved NL-Means Algorithm for Medical CT Image Denoising

ZHANG Dao-zhong, HUO Xiu-kun, LI Tao, ZHANG Wei

2013, 22(2): 297-302.

Abstract(665) PDF(1)

Abstract:
The medical CT Image will bring in noise when in the process of imaging. The noise can reduce the quality of image and affect the clinical diagnosis. Therefore, medical CT image denoising plays an important role in the diagnosis and treatment. This paper proposes the classical NL-Means algorithm at firse, then changes the denoising key role of the weighted kernel function. The experiment shows the algorithm for medical CT image denoising have certain effect, and can better preserve the detail information. For the PSNR, it can be improved by 2.59 dB at most.

CT Findings and Dynamic Analysis of Pulmonary Laceration

HUANG Yao-qu, LI Jun-hong, LIANG Zhen-hua

2013, 22(2): 303-308.

Abstract(580) PDF(2)

Abstract:
Objective: To investigate the CT findings of pulmonary laceration.Methods: The CT imagings of 51 cases with pulmonary laceration were analyzed retrospectively.Results: 249 lesions in total were found in the 51 patients.The CT findings included traumatic gas cyst(22 lesions),gas-fluid cyst(182 lesions) and fluid cyst(45 lesions).Various degree of pulmonary contusion around the lung laceration could be assessed.On dynamic follow-up observation of 20 patients,the gas cyst lesions could change to gas-fluid cyst or fluid cyst,and the gas-fluid cyst lesions could change to fluid cyst,but reversed variation was not found.Conclusion: The gas cyst,gas-fluid cyst and fluid cyst were the characteristic CT findings and dynamic morphology changes of pulmonary laceration.

MRI Evaluation of Placental Adhesive Disorders Treated by Interventional Therapy

MING Jian-zhong, ZHANG Xue-lin, LIU Tao, XIANG Cheng-xian

2013, 22(2): 309-315.

Abstract(543) PDF(1)

Abstract:
objective: To explore MRI signs and diagnostic value of MRI for placental adhesive disorders before and after interventional therapy.Methods: From Jan 2009 to Apr 2012,28 patients with placental adhesive disorders treated by embolization received MRI examination and compared with the results of operation and/or clinical diagnosis.The MRI findings before and after interventional therapy were retrospectively analyzed.Results: On MRI images,the placenta demonstrates a heterogeneous signal,isointense to myometrium.the myometrium become quite thin and it can be difficult to visualize in patients with placenta percreta.On Gadolinium-enhanced T1WI,the placental tissue invaded the myometrium in the shape of “garland” or “nodul”.MRI features of all patients by interventional therapy after three or twelve months showed that the placental tissue was confluent with the uterine wall and the myometrium demonstrates a heterogeneous signal.Conclusion: MRI can display the placental implantation site and myometrial invasion degree of placenta implantation;it has an important reference value and can accurately evaluate curative effect before and after interventional therapy to placental adhesive disorders.

The Imaging Analysis of Giant Cell Tumor of Bone in Atypical Locations

QUAN Qiang, WANG Xiu-ling, HU Chun-feng, RONG Yu-tao

2013, 22(2): 317-322.

Abstract(540) PDF(1)

Abstract:
Objective: To analyze imaging of giant cell tumor of bone in atypical Locations on plain film,CT and MRI.Methods: Nineteen cases with histologically confirmed giant cell tumor of bone in atypical Locations were reviewed.Radiography was performed in 19 cases,CT in 19 cases and MRI in 16 cases.Results: giant cell tumor of bone located at sacral in 9 cases,at ischial in 4 cases,at metatarsal in 2 cases,metacarpal,wrist,shoulder blades,lumbar each one case.Expanding growth and osteolytic destruction were on X–ray or CT,without hardened edge.MRI show low to intermediate signal on T1WI,hyperintensity on T2WI.Conclusion: Use of various imaging methods can improve the understanding of giant cell tumor of bone in atypical Locations,to make an accurate diagnosis.

64-Slice Spiral CT in Diagnosis of Nasal Cavity Lymphoma NK/T Cells Value

ZHENG Qiao, ZOU Jian-hua

2013, 22(2): 323-328.

Abstract(533) PDF(1)

Abstract:
Objective: Analysis of CT Imaging of nasal cavity Lymphoma NK/T cells,exploring its relatively specific performance.Methods: A retrospective analysis of 5 cases of nasal cavity Lymphoma NK/T cells confirmed clinical,surgical pathology and CT data.Result: 5 cases of NK/T cell lymphomas,both involving the nose or on the front vestibule,causing nasal swelling of the skin and subcutaneous tissue,adjacent to bone destruction or slightly less obvious,lesions larger density than even,mild enhancement.Conclusion: CT found in nasal cavity tumor on the front,without or with slight destruction or deformation of bone structure adjacent to nasal swelling under the skin on the back,you should consider NK/T-cell Lymphoma of the nasal cavity.

Application of 256 Multi-Detector Computed Tomography Enterography in Small Bowel Inflammatory Diseases

XIE Qian, DOU Ya-fang, LIANG Zong-hui, ZHU Quan-dong, ZHU Rui-jiang

2013, 22(2): 329-338.

Abstract(536) PDF(2)

Abstract:
To discuss the utility of MDCTE for evaluating inflammatory diseases of the small bowel.Materials and methods: At our institution,118 patients(male 53;female 65;mean age 48.5 years) with symptoms of suspected small bowel diseases underwent 256-MDCTE.Pertinent MDCTE and histopathology reports were reviewed.The CT appearances characteristic of small-bowel inflammatory bowel disease are described and illustrated in detail.Associated complications and extraenteric manifestations also are described.Results: Of 118 MDCTEs performed,there were 25 cases of small bowel inflammations(male 13;female 12;mean age 45.5 years).In all 12 cases of Crohn’s diseases,small bowel involvement was typically transmural,with characteristic skip lesions.CT features of active Crohn’s disease include mucosal hyper-enhancement,irregular wall thickening,mural stratification with a prominent vasa recta(comb sign),and mesenteric fat stranding.2 cases of ulcerative colitis characterized by a continuous pattern of bowel wall involvement,starting from the rectum,without evidence of skip lesions.Ulcerative colitis predominantly involved the large bowel but may extend to the terminal ileum.Extra-intestinal manifestations may occur but were uncommon.Mucosal hyper-enhancement along with circumferential and symmetric bowel wall thickening was present.There was mural stratification with enhancement of the inner mucosa and outer muscularis propria.Mesenteric hyperemia was present in the pericolonic fat;MDCTE demonstrated findings suggestive of intestinal tuberculosis in one patient by depicting ulcero-nodular with strictures,edema and thickening of the ileocecal region,the presence of necrotic mesenteric lymph nodes that were adjacent to a small-bowel thickening.There was 1 case of viral gastroenteritis and 7 cases of generalized small bowel enteritis with non-specific MDCTE features include bowel thickening and submucosal edema appreciable in the entire intestine.Mesenteric vessels were regularly opacified.MDCTE gave correct diagnosis in 21 cases,4 missed cases were all generalized small bowel enteritis.Conclusion: Our results demonstrated that MDCTE with peroral and intravenous contrast is useful in assessing small bowel inflammatory diseases;however,further studies are needed to determine and validate the full diagnostic and clinical potential of bowel imaging at MDCTE.

Value of Multi-Slice Spiral CT in the Diagnosis of Atypical Appendicitis

LI Shui-ting, JIANG Kui-ming, MAI Hui, ZHANG Jia-yun, SHI Li

2013, 22(2): 339-344.

Abstract(630) PDF(2)

Abstract:
Objective: To investigate the value of the multi-detector row computed tomography in the diagnosis of appendicitis with atypical clinical feature.Methods: 58 cases of appendicitis which were not initially considered on clinical presentation,were confirmed surgically and pathologically were collected,CT characteristics were retrospectively analyzed.Results: 54 of the 58 patients were correctly diagnosed on CT.It included: 6 cases of dissect abnormal appendicitis,22 cases of women of childbearing age appendicitis.19 cases of elderly appendicitis.11 cases of pediatric appendicitis.The direct CT signs of acute appendicitis were an charged appendix with wall thickening and appendicolith.Indirect signs included appendiceal perityphlitis and periappendicu1ar.Conclusion: Multi-detector row computed tomography is valuable for early diagnosis of appendicitis with atypical clinical feature.

Coronary Computed Tomography Angiography Using Low-kV and Tube Current Modulation in Subjects with Normal Body Mass Indices: A Feasibility Study

WANG Rui-qiong, FU Xia, DENG Jian-guo, LIU Jian-hua, CAI Li, QUAN Xiang, CHEN Xia, CAO Shen, SUN Jun

2013, 22(2): 345-352.

Abstract(555) PDF(0)

Abstract:
Objectlve: To assess the image quality and radiation dose of 80 kV electrocardiography(ECG)-gated CCTA in subjects with a normal body mass index(BMI),compared to 120 kV ECG-gated CCTA.Method: The CCTA images of 140 subjects with BMIs ＜ 25 kg/m² were analyzed.Seventy subjects underwent 120 kV CCTA,and the other 70 subjects underwent 80kV CCTA.Two blinded observers independently evaluated the subjective image quality of the coronary arteries.The objective image quality(signal-to-noise ratio(SNR) and contrast-to-noise ratio(CNR)) and radiation dose were also measured in each group.Results: Although the objective image quality of the 80 kV protocol images was significantly poorer than that of 120 kV protocol images(P ＜ 0.05),there was no significant difference in the subjective image quality between the two groups(P ＞ 0.05).The radiation dose was reduced by 12mSv with the 80 kV protocol and by 82% with the 80 kV and ECG-based tube current modulation than one with the 120 kV protocol(P ＜ 0.05).Conclusion: The low tube voltage CCTA protocol using 80 kV allows significant reduction of the radiation dose without impairing the subjective image quality in subjects with normal BMIs.

The Value of MSCT on Postoperative Complications Following Splenectomy

WANG Jun, HUANG Si-yun, DONG Zhi, LUO Yan-ji, WU Ling, FENG Shi-ting

2013, 22(2): 353-362.

Abstract(565) PDF(1)

Abstract:
Objective: To investigate the value of multislice computed tomography(MSCT) diagnosing the complications following splenectomy.Methods: Retrospectively analyzed the abdominal MSCT appearances of 151 patients who had undergone full splenectomy in our hospital during January 2009 to December 2012.Results: Postoperative complications occurred in 60 patients(39.7%),including short-term complications(51 patients) and long-term complications(9 patients).Short-term complications: Wound infection(2 patients),incisional hernia(1 patients),subphrenic abscess(8 patients),pleural effusion and atelectasis(21 patients),thrombosis of vein(14 patients),Long-term complications: cavernous transformation of the portal(1 patients) and ectopic splenic autotransplantation(8 patients).Conclusion: MSCT is the optimal method on discovering the various imaging findings of postoperative complications following splenectomy.

Development of CNT Cathode Based X-ray Source and Imaging Technology

CHEN Yao, CHEN Ting, GUI Jian-bao, HU Zhan-li, Peter Z. WU, XIA Dan, ZHENG Hai-rong

2013, 22(2): 363-372.

Abstract(656) PDF(3)

Abstract:
Carbon nanotube(CNT) cathode based field emission X-ray source and imaging techniques as an important development for X-ray CT technology,has generated much interest in recent years.Compared to the more traditional thermal emission X-ray source,CNT X-ray source possesses several desirable attributes such as miniaturization,fast response time,efficient-focusing and improved control of emitted electrons.Thus,an imaging tool based on these attributes will contribute significantly to the field of X-ray imaging within both medicine and industry.In this paper,the development of CNT cathode based X-ray source and imaging methodologies will be discussed.

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2013 Vol. 22, No. 2