CT理论与应用研究

Review of Developments of the Dual Energy X-ray Absorptiometry Techniques

LI Chan, LI Liang, CHEN Zhi-qiang

2014, 23(5): 717-730.

Abstract(864) PDF(21)

Abstract:
Due to the serious increasing of osteoporosis, how to obtain accurate bone mineral density has arouse greater attention all over the world. With the development of medical technology, dual energy X-ray absorptiometry is widely applied in the diagnosis of osteoporosis because of its accuracy, low dose and variety. In this paper, we state the concept of bone mineral density, and summarize the methods and the sites of measurement in clinical diagnose of osteoporosis. It focuses on the fundamentals of dual energy X-ray absorptiometry, explores in great depth the key techniques, and elaborates current problems and limitation in both hard ware and software. Accordingly, this paper also discusses and predicts the future development tendency of dual energy X-ray absorptiometry's future development and improvement.

The Review of High Energy Dual-energy X-ray DR Imaging and Material Recognition Technology

CHEN Zhi-qiang, ZHAO Tiao, LI Liang

2014, 23(5): 731-742.

Abstract(780) PDF(8)

Abstract:
This paper is concerned with high energy dual-energy X-ray imaging and identification and detection of objects, introduces the background of dual-energy X-ray DR imaging technology from single energy, low energy dual-energy to high energy dual-energy and elaborates the principle, technical characteristics and improved methods of high energy dual-energy X-ray imaging material recognition. The nature of material recognition feasibility of this technology is mainly discussed. It also introduces the latest advances and challenges facing the field.

Research on CT Imaging Method Along a General Scanning Trajectory

LIU Hua, CHEN Ping, PAN Jin-xiao

2014, 23(5): 743-750.

Abstract(777) PDF(4)

Abstract:
In the application of industrial CT imaging, The X-ray energy mismatch to the effective thickness and traditional scanning is difficult to preserve the data integrity of projection due to the limit of complex-structure's shape, structure and so on. Therefore, changing the general scanning trajectory to make up for the deficiency of projection data, and then deriving the iterative reconstruction algorittun along a general scanning trajectory. First of all, in the base of general scanning trajectory, we combine the knowledge of analytic geometry with the projection to obtain the projection matrix. The second, the iterative reconstruction algorithm is no binding trajectory, so we study the iterative reconstruction algorithm along a general scanning trajectory. Finally, according to the numerical simulation of small cone-beam angle, lager cone-beam angle scanning and different thickness of structure testing to verify the correctness and feasibility of the algorithm. For the different thickness of structure, compared to the traditional circle scanning, this method is better for preserving the data integrity of projection and improving the quality of reconstructed image.

A CT Reconstruction Algorithm Based on Contourlet Transform and Split Bregman Method

DENG Lu-zhen, FENG Peng, CHEN Mian-yi, HE Peng, ZHANG Wei, WANG Jian, LI Zhi-chao, WEI Biao

2014, 23(5): 751-759.

Abstract(707) PDF(4)

Abstract:
Gradient operator has some shortages in sparse representation in Computed Tomography (CT) image reconstruction algorithms, while Contourlet transform can represent image better because it contains direction information of images. Based on this, this paper introduce Contourlet transform to sparse CT image reconstruction. As a starting point, we propose an algorithm which combine Contourlet transform with Total Variation (TV) and then we use the Split Bregman method to solve the optimization problem. The experimental results show that the reconstructed results using the proposed algorithm with fewer projection can suppress noise effectively, and reduce the artifacts, which indicate that the proposed algorithm is more suitable with sparse sampling.

Image Fusion in Combination of the Improved IHS Transform and Wavelet Transform

FAN Hua, ZHAO Guo-chun, HAN Yan-jie, LIU Ming-jun, LI Xiao-qin, SUN Yong-jun

2014, 23(5): 761-770.

Abstract(810) PDF(3)

Abstract:
In the analysis and IHS transform we found that total intensity is obtained through a third from each red, green and blue in calculation of intensity of IHS transformation. As the human eye is the most sensitive to green (60%), followed by red (30%), moreover is blue (10%), therefore, the formula of intensity component has been modified in this paper. On this basis, a image fusion method of combined the improved IHS transform with wavelet transform has been presented. First, the improved IHS transform for multispectral image is conducted, and the I component and high-resolution panchromatic image are decomposed using wavelet transform, respectively, and the low frequency and high frequency coefficient of high-resolution panchromatic image are fused with those of the I component based on local energy and on local variance, respectively. Finally, IHS inverse transformation is conducted, and the fusion result images are obtained. Results show that the proposed method in this paper has an advantage in keeping the source image spectral characteristics and also keep the spatial fine structure of the source image, and decrease distortion degree of fused image.

Rotated Staggered Finite-difference Modeling for Quasi-P Wave in VTI Medium

YIN Xing-yao, PU Yi-tao, LIANG Kai, SUN Rui-ying

2014, 23(5): 771-783.

Abstract(705) PDF(1)

Abstract:
Using the rotated staggered-grid of finite difference form, the numerical modeling of the first-order stress-velocity equation of quasi-P wave in VTI (vertical axis of symmetry of the transversely isotropic) medium is achieved. Under the PML boundary conditions and the stability condition, high precision wave field snapshots and synthetic record of complex models such as Marmousi are obtained. Besides, we analyze the effect of the anisotropy on seismic wave. The results show that the rotated staggered-grid of finite difference can get high precision seismic simulation data, and the PML boundary has better absorption effect.

Electromagnetic Field's Spatial Distribution of a Horizontal Magnetic-dipole in Layered Media

HUANG Ye-zhong, XIONG Bin, LUO Tian-ya, LIU Yun-long

2014, 23(5): 785-796.

Abstract(758) PDF(2)

Abstract:
In allusion to the case that dielectric constant and magnetic permeability vary with the depth of rock stratum, this paper presents the horizontal or vertical spatial distribution feature and corresponding variation law of electromagnetic field of a horizontal magnetic-dipole source. Taking advantage of the algorithm of Hankel J₀ transform linear filters (241 points) and Hankel J₁ transform linear filters (241 points) suggested by Kong, we discuss the spatial distribution characteristic of a horizontal magnetic-dipole source as media dielectric constant and magnetic permeability make changes in the homogeneous earth and two layers geoelectric structure. The result indicates a negative correlation between the amplitude of magnetic field component H_x and magnetic permeability, while a positive correlation between H_z (E_y) and magnetic permeability; meanwhile, the change of dielectric constant scarcely affects magnetic field in the low frequency electromagnetic sounding.

Analysis of Ancient Liao Zhu by Using Micro-CT from Machuan Cemetery

GU Zhou, YANG Yi-min, QI Xue-yi, LIU Wen-ge, SONG Guo-ding

2014, 23(5): 797-803.

Abstract(765) PDF(2)

Abstract:
In this study, the Micro-CT was first applied to study ancient Chinese Liao Zhu. The results suggested that the two Liao Zhu were glass beads, not faience beads, and the internal structure of Western Zhou faience beads were distinct from early glass beads. Micro-CT was proved to be a new method to distinguish Liao Zhu. As shown in CT slices and 3D models, the shape of Warring State glass spherical air bubbles are different from West Han glass oblate air bubbles. Many irregular and shape cornered crevices can also be found in M118-100. The differences in intemal structure inferred their differences in manufacture process. The Warring State glass bead M118-100 should be manufactured by mold-casting techniques, and the West Han glass bead M156-23 was possibly manufactured by the drawn technique. Micro-CT provided an effective method to analyze the manufacturing process of ancient glass in a nondestructive manner.

A Practice on Parallel Reconstruction Algorithm of High Resolution Cone Beam Micro-CT Based on NVDIA GPU Graphic Card

ZHENG Hai-liang, LI Xing-dong, WANG Zhe, WEI Cun-feng, CHANG Tong

2014, 23(5): 805-814.

Abstract(878) PDF(5)

Abstract:
Objective: To explore the feasibility of parallel computing applying in high-resolution cone beam micro-CT reconstruction and its impact on reconstruction speed. Method: Allocating video memory to projection pictures and reconstruction voxels in GPU graphic card (NVIDIA QUADRO K5 000, Video Memory 4G) with parallel computing, and allocating thread to each pixel for adjusting and filtering projection picture, and then allocating thread to each voxel for Back Projection, thus, all section reconstruction is implemented in graphic card. Result: Less than 9 minutes spent for 2 048 × 2 048 × 128 pixel matrix reconstruction, which is equal to 1/3 of data gathering tirne and 2% of CPU based reconstruction, under the condition that one voxel is recorded by 32 float, and each projection picture size is 2 048 × 1 536, and 1 800 projections are gained in one scanning. Conclusion: Parallel computing applied in cone beam CT reconstruction can greatly increase reconstruction speed and data gathering can simultaneously operate with reconstruction.

Explore of Different Line-pairs Test Spatial Resolution CT

ZHANG Wei-guo, CAO Yu-ling, GUO Zhi-min, NI Pei-jun, ZUO Xin, WANG Xiao-yan, HAO Li-ping

2014, 23(5): 815-820.

Abstract(970) PDF(3)

Abstract:
The spatial resolution of a CT system is important, but the two established methods to measure the spatial resolution, MTF and line-pairs. Make the line-pairs no unified standard, commonly use line-pairs has bar, hole and quadratic shape. In this paper, through theoretical analysis and test to determine the different line-pairs to test the results of the spatial resolution of CT differences and reasons.

Imaging Diagnosis and Differential Diagnosis of Fat-containing Primary Hepatocarcinoma

MAO Mi-mi, LI Hong-jiang, FU Ai-yan, SHEN Ai-jun, SI Hai-feng, LI Chun-sun

2014, 23(5): 821-828.

Abstract(714) PDF(3)

Abstract:
Objective: To investigate the value of CT and MRI in diagnosis and differential diagnosis of fat-containing primary hepatic carcinoma. Method: CT and MR imaging features of twenty-two patients with pathologically confirmed fat-containing primary hepatic carcinoma were retrospectively analyzed. Result: In 22 cases with fat-containing primary hepatic carcinoma,16 cases showed a giant mass, 4 cases were nodular type , and 2 cases were diffuse type. Of 22 cases, there were 17 cases of single lesion and 5 cases of multiple lesions. 1 lesion with fatty tissue can be discovered in every case of multiple lesions. 18 cases appeared as mainly solid masses, and fat was scattered with a small cluster distribution within the masses; 4 cases appeared as mainly fat masses and less solid components, and intratumoral fat showed a spherical performance. CT can show patchy and globular fat density within the lesions, MRI with fat suppression and chemical shift imaging of gradient echo sequence can identify the presence of fat. All 22 cases showed "fast in, fast out" enhancement features on dynamic contrast-enhanced imaging, and pseudocapsule was observed in 15 cases. Conclusion: CT and MRI can well demonstrate the imaging features of primary hepatic carcinoma and the adipose tissue within the tumor, which is valuable for diagnosis and differentiation.

The Value of Dual-source CT Angiography in the Diagnosis and Follow-up of the Aorta Coarctation

NING Wu, LUO Song, ZHANG Long-jiang

2014, 23(5): 829-834.

Abstract(699) PDF(1)

Abstract:
Objective: To evaluate the value of CT angiography (CTA) in the diagnosis and follow-up of coarctation of the aorta. Methods: A retrospective analysis of 17 patients with coarctation of the aorta was performed, 6 patients underwent follow-up CT following bypass graft surgery. Results: Of 17 patients diagnosed as aortic coarctation, 10 patients were males, 7 were females. Eight cases were next to the ductus arteriosus, 4 cases before the catheter, 5 cases of in the catheter. Five patients underwent surgical bypass graft surgery, 1 case with vascular replacement surgery and 1 case with balloon angioplasty, 3 cases were associated with other malformations, including double superior vena cava (n=l), patent ductus arteriosus (n= 1), anomalous pulmonary venous drainage (n = 1). Significant collateral vessels were observed in all patients, including the enlarged bronchial arteries, intercostals arteries and internal thoracic arteries. The bypasses of 5 operated-patients were patent. Conclusions: CTA can reliably diagnose aorta coarctation, show collateral vessels, and play a very important role in the postoperative follow-up.

Clinical Diagnosis Value of 128-slice Spisal CT compared to X-ray CAG

ZHANG Zhi-guo, YU Qing-wen, SUN Qing-ju, ZHOU Su-ning

2014, 23(5): 835-841.

Abstract(702) PDF(1)

Abstract:
Aim: To explore the value of 128-slice spiral CT in evaluating coronary artery disease by comparison with coronary arteriography. Methods: a total of 56 consecutive patients who showed coronary heart disease clinical symptoms or high risk factors in our hospital from March 2010 to January 2012, were given 128-slice spiral CT and given coronary arteriography in the 3-12 days. CAG results as the gold standard, evaluation of CTA coronaty atherosclerotic plaque the clinical value of quantitative analysis and qualitative analysis as well as to the coronary artery opening the discovery of abnormal detection rate. Result: according to the results of CTA, in 56 cases of patients, a total of 673 coronary artery segments can be evaluated, containing normal blood segments 505. 152 narrow or blocked segments caused by coronary artery plaques in 167 narrow or blocked and 4 abnormal coronary openings. In different branch of coronary artery, the incidence of mixed plaque than calcified plaques and soft plaque, the total incidence of different characteristics plaques in LMA (11%) and the incidence of soft plaque (0) are lower than those in LAD and RCA, and statistical difference was statistically significant (P ＜ 0.05). According to the CTA and CAG imaging quality, The accuracy of the plaques properties of CTA'was better than that of CAG, opening coronary anomalies shows that the accuracy is better than that of the CAG. Conclusion: 128-slice spiral CT coronary angiography as a noninvasive imaging method, the determination of coronary atherosclerotic plaque characteristics in CTA was superior to X-ray CAG. Opening coronary anomalies shows that the accuracy is better than that of the CAG and statistical difference was statistically significant (P ＜ 0.05). In some extent, the CTA can selectively instead of X-ray coronary angiography.

Comparison between Two Materials of Bone Graft in Guided Bone Regeneration by CT Image Analysis

WANG Guo-shi, WEI Ming-gui, LI Shao-wei, SHA Yan-zhi

2014, 23(5): 843-850.

Abstract(790) PDF(2)

Abstract:
Objective: To compare the changes between Bio-Osten bone meal and Bio-Oss bone meal during the period of guided bone regeneration (GBR) in immediate implanting according to the data from the image by spiral CT scan. Methods: 15 patients who receive immediate implanting and GBR process in anterior teeth, were divided randomly into two groups including experimental group (Bio-Osten bone grafts, n = 7) and control group (Bio-Oss, n = 8). During dental implanting, the two groups were used Bio-Osten bone meal and Bio-Oss bone meal respectively and took spiral CT to scan the implanting area in 1 week, 3 months, 6 months after the procedures. According to the information from the image by CT scan, the volumes of bone meal in both groups were measured using Simplant analysis system .The remaining volume ratios were calculated in two groups in 3 months, 6 months after the procedures and analyzed statistically between two groups by the SPSS 16.0. Results: 3 months after operation, the absorption ratios were 41.51% ± 5.87%, 49.30% ± 5.78% in Bio-Osten group and Bio-Oss group, respectively. 6 months after operation, the absorption ratios were 58.02%±5.67%, 70.26%± 10.64%, respectively. There were significant difference between two groups (P ＜ 0.05) in both 3 months and 6 months. Conclusion: According to CT image, Bio-Osten and Bio-Oss have similar role in bone induction and similar biological absorption. In comparison, Bio-Osten was absorpted more slowly than Bio-Oss. Maybe Bio-Oss guided bone regeneration faster than Bio-Osten.

MRI Findings of the Subcutaneous Prepatellar Bursitis

DING Chang-qing, PAN Rong-lei, XU Ruo-feng, DING Ai-lan, LIU De-hai, SUN Ying-ying, LUO Hui, DAI Lan-lan

2014, 23(5): 851-856.

Abstract(762) PDF(1)

Abstract:
Objective: To investigate the MR/findings and differential diagnosis of the subcutaneous prepatellar bursitis (SPB). Methods: A retrospective analysis of 0.35T MR/data of 28 cases with the SPB confirmed clinically Results: 27 patients had a history of acute or chronic knee injury, 1 patients with ankylosing spondylitis. All were with painless swelling of anterior knee. MR/was characterized by a oblateness with medium or low signal in T1WI and medium or high signal in T2WI clingy to the patella. Size: 2.8cm×0.5cm×1.9cm~14.8cm×3.6cm×9.3cm with an average of 6.6cm×2.0cm×3.7cm. Axis MR/showed better. Conclusion: It is helpful for early diagnosis of SPB to understand the features of the clinical and MR/manifestations.

Clinical Value of CTA Applied in Coronary Artery Stenosis

LI Wei

2014, 23(5): 857-862.

Abstract(802) PDF(1)

Abstract:
Objective: Comparative analysis of multi slice spiral CT coronary angiography (CTA) and digital subtraction angiography (DSA) in the accuracy and sensitivity of evaluating coronary artery stenosis, in order to explore the clinical value of CTA for detecting coronary artery stenosis. Methods: 39 patients were diagnosed or suspected with coronary heart disease from 2011 September to 2013 September in our hospital. They were examined by CTA, and DSA within two week before or after the CTA examination. Then the CTA and DSA test results were compared and analyzed, the specificity and sensitivity of CTA and DSA of coronary artery were figured out. Results: 39 patients with 290 vessels, CTA found 220 coronary artery stenosis; DSA found 223 coronary artery stenosis. With DSA as the standard, the sensitivity, specificity, positive predictive value, negative predictive value and the detective accuracy of CTA detection is 92.44%, 96.15%, 97.35%, 93.46% and 94.96%. Conclusion: CTA can clearly show the changes of coronary artery wall thickening and stenosis, aortic wall plaque and calcification. It is an noninvasive method for the diagnosis of coronary artery disease.

Discrimination of True and False Lumen in Dissection of Aorta for Debakey Ⅰ and Ⅲ B Patients:A Quantitative Analysis

ZHAO Lei, YUAN Xiao-jun, BAO Li-li, LIU Ai-shi

2014, 23(5): 863-869.

Abstract(793) PDF(1)

Abstract:
Objective: The purpose of this study based on the measurement and analysis of absolute area, relative area and the average attenuation for true and false lumen in aortic dissection for distinguishing. Methods: A retrospective analysis of May 2011, to November 2013 with acute chest pain of 65 cases of suspected aortic dissection patients, the median age was 54 years, 49 cases of men and 16 cases of women. Comply with the inclusion criteria and exclusion criteria. The patients were selected for standard aorta CTA. The graphic indicators was measured by absolute area (and calculated relative area), the average attenuation for true and false lumen. Compare the absolute area, relative area and attenuation of true and false lumen. The absolute area, relative area and attenuation of AUC were calculated by ROC. Results: The average absolute area of true lumen was (656.30±386.21) mm², the average absolute area of false lumen was (951.21 ±464.32) mm², by paired sample t test, t = 49.318, P = 0.000, the difference was statistically significant; The Average relative area of true lumen was 0.33±0.14, The Average relative area of false lumen was 0.67±0.14, by paired sample t test, t=34.235, P = 0.000, the difference was statistically significant; Average true lumen attenuation value was (234.02 ±83.53) Hu, false lumen attenuation value was (238.54 ± 87.40) Hu, by paired sample t test, t = 0.914, P = 0.361, there was no statistically significant difference; the absolute area, relative area and the attenuation of AUC was 0.846, 0.950 and 0.525, P value was 0.000, 0.000, and 0.092, respectively. Conclusion: The relative area had high sensitivity and specificity that was used to identify the true and false lumen.

The CT Diagnosis of Cystic Type Intestinal Duplications

WU De-hong, YANG Song, GONG Xiao-hong, FU Chuan-ming, LIU Chao, CHEN Ping-you

2014, 23(5): 871-876.

Abstract(695) PDF(1)

Abstract:
Objective: to analyze the CT manifestations of cystic type intestinal duplications and improve the diagnostic level of this disease. Methods: The clinical data of 11 cases of child cystic type intestinal duplications verified by postoperative pathologic examination were retrospectively analyzed and summarized for the CT manifestations. Results: 8 male and 3 female cases all showed cystic type intestinal duplications. 9 cases were outside the intestinal wall and 2 cases inside it. The CT manifestations abenteric cases showed a single-room low density mass, whose cystic wall was a little thick and showed an obvious homogeneous enhancement in CT scanning. 5 abenteric cases showed double-deck "halo sign". The CT manifestations of inside intestinal type showed intracavitary cystic mass attached to the intestinal wall, which manifested "double-arc sign" in the axial CT scanning. Conclusion: The clinical manifestations of cystic type intestinal duplications were not obvious, however, its CT manifestations had a few features, which showed great value in the preoperative and differential diagnosis of child cystic type intestinal duplications.

The X-ray Performance of Normal Fat Pad of Elbow and its Clinical Significance

ZOU Wen-yuan, LI Sheng, LIU Yuan-yuan, CAO Yang, ZHOU Lin, XIONG Liang, XU Guan-zhen

2014, 23(5): 877-882.

Abstract(718) PDF(2)

Abstract:
Objective: To raise awareness on the X-ray performance of normal elbow fat pad. Methods: Analyzed 182 cases of X-ray performance on normal elbow fat pad. Observed the frequency of the fat pad occurrence, position, shape, and density on the standard lateral X-ray, and measured the maximum thickness. All the subjects were divided into two groups by age, 〈 18 years (juveniles) and ≥ 18 years (adult), and then male and female groups according to gender. All the data were collected for statistical analysis. Results: 182 cases were eligible for the study, including 132 adults and 50 juveniles. The anterior fat pads (AFP) were visible and the posterior fat pad (PFP) were invisible in all cases. In the normal lateral X-ray of elbow, the anterior fat pad was close to the distal end of the humerus and extrude to the front with a sharp triangle change angle of which points to the proximal end. The outer edge of AFP was straight,while the density was lower than the muscles and bones, surrounded The thickness value of AFP of juvenile s and adults were difference (t = 2.468, P = 0.015 ＜ 0.05); The thickness (3.42±0.71)mm and (3.13 ±0.70)mm with a obvious value of AFP of the male and female groups were (3.21 ±0.70) mm and (3.22± 0.73) mm with no difference (t = 0.085, P = 0.932 ＞ 0.05). The up and down limit of 95% reference range of AFP of adult were 4.50 mm and 1.76 mm. And the up and down limit of 95% reference range of AFP of juvenile were 4.81 mm and 2.03 mm. Conclusions: The anterior fat pad (AFP) was visible while the posterior was invisible. There was an obvious difference of thickness value of AFP between the juveniles and adults, but no difference between men and women. Correctly identifying of the X-ray of the performance of fat pad can greatly help to evaluate the condition of the elbow trauma patients.

Review of Computed laminography

WAN Xin, LIU Xi-ming, WU Zhi-fang

2014, 23(5): 883-892.

Abstract(776) PDF(6)

Abstract:
In computed tomography (CT), samples usually need to be scanned in 360 degree to obtain sufficient projection data. However, there exist difficulties for CT in inspecting large or flat samples because of geometry limitations and the high absorption close to the sample surfaces. Under these circumstances, computed laminography (CL) provides an effective alternative. Firstly, this paper summarizes researches at home and abroad recently; Secondly, principle, reconstruction algorithms and applications of CL are introduced systematically; At last, CL is compared with CT in image quality.

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2014 Vol. 23, No. 5