改进的先验图像约束的压缩感知重建方法用于低剂量X-线CT

低剂量CT重建已成为当前X-线CT成像的研究热点。针对低剂量CT成像,本文提出一种改进的先验图像约束的压缩感知重建方法。新方法首先对CT线积分投影数据采用惩罚加权最小二乘方法进行降噪恢复,接着对恢复后的投影数据进行滤波反投影重建,然后以重建图像作为先验图像应用先验图像约束的压缩感知方法进行统计迭代重建。实验结果表明,同已有的先验图像约束的压缩感知重建方法相比,新方法能够更有效地抑制低剂量CT重建图像中的噪声和条形伪影,同时较好地保持图像的空间分辨率。

Projection registration of X-ray image and CT image

A methodology for alignment of an X-ray image and a CT image, based on the Chamfer 3-4 distance transform and simulated annealing optimization algorithm is presented. Firstly, an initial transformation matrix is constructed. For the convenience of computing, geometric models of the X-ray device to reconstruct the calibration matrix are used. Then, by defining the distance between the 3-D protective and the 2-D object image, we optimize this distance matching problem, using the simulated annealing algorithm. This method is also integrated into medical intra-operation, dealing with the data set acquired from 3-D image workstation and active navigation.

3D characterization and analysis of pore structure of packed ore particle beds based on computed tomography images

Methods and procedures of three-dimensional （3D） characterization of the pore structure features in the packed ore particle bed are focused. X-ray computed tomography was applied to deriving the cross-sectional images of specimens with single particle size of 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10 ram. Based on the in-house developed 3D image analysis programs using Matlab, the volume porosity, pore size distribution and degree of connectivity were calculated and analyzed in detail. The results indicate that the volume porosity, the mean diameter of pores and the effective pore size （d50） increase with the increasing of particle size. Lognormal distribution or Gauss distribution is mostly suitable to model the pore size distribution. The degree of connectivity investigated on the basis of cluster-labeling algorithm also increases with increasing the particle size approximately.

Measurement and analysis of defects in high-performance concrete with three-dimensional micro-computer tomography

In order to investigate the effects of two mineral admixtures （i. e., fly ash and ground slag）on initial defects existing in concrete microstructures, a high-resolution X-ray micro-CT（ micro-focus computer tomography）is employed to quantitatively analyze the initial defects in four series of highperformance concrete （HPC）specimens with additions of different mineral admixtures. The nigh-resolution 3D images of microstructures and filtered defects are reconstructed by micro- CT software. The size distribution and volume fractions of initial defects are analyzed based on 3D and 2D micro-CT images. The analysis results are verified by experimental results of watersuction tests. The results show that the additions of mineral admixtures in concrete as cementitious materials greatly change the geometrical properties of the microstructures and the spatial features of defects by physical-chemistry actions of these mineral admixtures. This is the major cause of the differences between the mechanical behaviors of HPC with and without mineral admixtures when the water-to-binder ratio and the size distribution of aggregates are constant.

农民大棚肺动物模型影像表现的多排螺旋CT研究

目的应用多排螺旋CT观察大棚肺动物模型的影像表现。方法取26只成年健康豚鼠,随机分为实验组(20只)和对照组(6只)。实验组分为雾化吸入组(A1,10只)和鼻滴吸入组(B1,10只),A1组分为持续吸入14d的A11组(5只)及持续吸入90d的A12组(5只)。B1组分为持续鼻滴14d的B11组(5只)及持续鼻滴90d的B12组;对照组分为雾化吸入生理盐水组(A2,3只)及鼻滴吸入生理盐水组(B2,3只)。分别按不同的时间给予实验干预,然后按照不同的时间进行多排螺旋CT扫描,观察各组的CT表现。结果 A1组14天之前CT扫描肺部无异常表现,第14天后的不同时间出现肺部斑片状磨玻璃样影或结节影。在第90天扫描时,A11组可出现不同程度纤维索条影,A12组可出现磨玻璃样斑片影及小磨玻璃结节影同纤维索条影混合存在的征象。B1组于14天之内均出现肺部异常表现,可见两肺弥漫性磨玻璃样影、两肺多发大片状实变影或斑片及小结节样磨玻璃样影。第90天扫描时,B11组豚鼠均出现程度不等的纤维索条影,B12组可见磨玻璃样斑片影及结节影同纤维索条影混合存在的征象。对照(A2、B2)组各时间点行CT检查均显示双肺也清晰,未见斑片状或结节状影。结论农民肺动物模型的多排螺旋CT表现为,两肺弥漫性磨玻璃影或大片实变影或局部磨玻璃样影或弥漫或多发磨玻璃样结节影,慢性期出现不同程度的索条影,持续反复接触过敏原者可出现磨玻璃影与纤维索条影混合存在。

A case of primary malignant fibrous histiocytoma of the pancreas: CT and MRI findings

Primary malignant fibrous histiocytoma (MFH) of the pancreas is rare and a distinct clinical entity. We report a case of recurrence of pancreatic MFH with computed tomography (CT) and magnetic resonance imaging (MRI) findings. A 67-year-old man presented with a history of decreased body weight over the past 6 mo. Abdominal CT revealed a large, multilocular cystic mass in the head of the pancreas with obvious atrophy in the body and tail of the pancreas. After 6 mo postoperatively, MRI demonstrated a recurrent large mass in the primary area of the head of the pancreas. The lesion was heterogeneous, hypointense to the liver on T1-weighted imaging, and heterogeneously hyperintense to the liver with a hypointense area in the central part of the tumor on fat-saturated T2-weighted imaging. Contrast- enhanced T1-weighted imaging demonstrated a large multilocular cystic mass with a cystic wall, fibrous septa and enhancement of solid components. To the best of our knowledge, this is the first report on recurrence of primary MFH of the pancreas, and the first with MRI findings.

Calcified reticulate rind sign:A characteristic feature of gossypiboma on computed tomography

We herein report a gossypiboma resulting from a retained surgical swab, which had been left in peritoneum for 20years after appendectomy. CT revealed a cystic mass with a calcified reticulate rind. Subsequent surgery and pathological examination showed a gossypiboma. A simple experiment, using a barium-soaked surgical swab demonstrating similar CT appearance, supported our postulation that calcium deposition on the reticulated fibers of a surgical swab could generate such a characteristic 'calcified reticulate rind' sign. We believe that identification of this CT sign facilitates the diagnosis of gossypibomas.

Diagnostic Value of CT Colonography in Colorectal Carcinoma

OBJECTIVE To investigate the value of CT colonography （CTC） in diagnosis and preoperative staging of colorectal carcinoma.METHODS CTC was performed on 33 patients who were suspected of having colorectal carcinoma. The results of CTC were compared with those of a pathological examination.RESULTS Among the 22 patients who were diagnosed with colorectal carcinoma by CTC, 20 cases were confirmed by pathology. The diagnostic sensitivity and specificity were 100% （20/20） and 84.6% （11/13） respec- tively. The accuracy of showing carcinoma pathologic patterns was 90% （18/20）. The sensitivity and specificity were both 100% in the mass type; 77.8% and 100% in the infiltrating type; 100% and 85.7% in the ulcerated type. The accuracy of staging Dukes＇ carcinbma was 75%. The sensitivity and specificity were 100% and 94.1% for Dukes＇A; 80% and 73.3% for Dukes＇ B： 60% and 100% in Dukes＇ C： 71.4% and 100% for Dukes＇ D.CONCLUSION CTC produces a high success rate and provides considerable diagnostic information for both an accurate diagnosis of colorectal carcinoma and staging before operation,

Establishing models of portal vein occlusion and evaluating value of multi-slice CT in hepatic VX2 tumor in rabbits

AIM： To establish models of portal vein occlusion of hepatic VX2 tumor in rabbits and to evaluate the value of multi-slice CT. METHODS： Forty New Zealand rabbits were divided into 4 groups according to digital table： Immediate group （group A; transplantation of tumor immediately after the portal vein occlusion）, 3-wk group （group B; transplantation of tumor at 3 wk after the portal vein occlusion）, negative control group （group C） and positive control group （group D）, 10 rabbits in each group. Hepatic VX2 tumor was transplanted with abdominalembedding innoculation immediately after the portal vein occlusion and at 3 wk after the portal vein occlusion. Meanwhile, they were divided into negative control group （Left external branch of portal vein was occluded by sham-operation, and left exite was embedded and inoculated pseudoly） and positive control group （Transplanted tumor did not suffer from the portal vein occlusion）. All rabbits were scanned with multi-slice CT. RESULTS： All 40 animals were employed in the final analysis without death. Tumor did not grow in both immediate group and 3-wk group. In 3-wk group, left endite was atrophied and growth of tumor was inhibited. The maximal diameter of tumor was significantly smaller than that in positive control group （2.55±0.46 vs 3.59±0.37 cm, t = 5.57, P 〈 0.001）. Incidences of metastasis in the liver and lung were lower in 3-wk group than those in positive control group （10% vs 400, and 90% vs 100%, respectively）. The expression intensities of the vascular endothelium growth factor （VEGF） in groups A, B, C and D were 0.10±0.06, 0.66±0.21, 0.28±0.09 and 1.48±0.32, respectively. VEGF expression level in the test group A was significantly lower than that in the negative control group C （t = 5.07; P 〈 0.001）.In addition, VEGF expression in the test group B was significantly lower than that in the positive control group D （t = 6.38; P 〈 0.001）. Scanning with multi-slice CT showed that displaying rate of hepatic artery branches was obviously lower in grade Ⅲ（40%） than that in grade Ⅰ（70%） and Ⅱ（100%） （P 〈 0.05）; but there was no significant difference in displaying rate of the portal vein at various grades. Values of blood flow （BF） of the liver, blood volume （BV）, mean transit time （MTT） and permeability of vascular surface （PS） were lower in the immediate group and 3-wk group than those in control groups, but values of hepatic arterial fraction （HAF） were increased. Significant positive correlations were existed between BF and BV （r = 0.905, P 〈 0.01）, and between BF and PS （r = 0.967, P 〈 0.01）, between BV and PS （r = 0.889, P 〈 0.01）. A significant negative correlation existed between PV and HAF （r = -0.768, P 〈 0.01）, between PS and HAF （r = -0.557, P 〈 0.01）. The values of BF, BV and PS had a positive correlation with VEGF （rBF = 0.842, rBV = 0.579, rPS = 0.811, P 〈 0.01） . However, there was no significant correlation between the values of MTT and HAF and the VEGF expression （rMTt = 0.066, rHAF = -0.027）. CONCLUSION： Ligating the left external branch of portal vein is an ideal way to establish models of portal vein occlusion in rabbits with hepatic VX2 tumor. Multi slice CT plays a key role in evaluating effect of portal vein occlusion.

A PRELIMINARY STUDY ON COMPARISON AND FUSION OF METABOLIC IMAGES OF PET WITH ANATOMIC IMAGES OF CT AND MRI

Objective. To compare and match metabolic images of PET with anatomic images of CT and MRI. Methods. The CT or MRI images of the patients were obtained through a photo scanner, and then transferred to the remote workstation of PET scanner with a floppy disk. A fusion method was developed to match the 2- dimensional CT or MRI slices with the correlative slices of 3- dimensional volume PET images. Results. Twenty－ nine metabolically changed foci were accurately localized in 21 epilepsy patients’ MRI images, while MRI alone had only 6 true positive findings. In 53 cancer or suspicious cancer patients, 53 positive lesions detected by PET were compared and matched with the corresponding lesions in CT or MRI images, in which 10 lesions were missed. On the other hand, 23 lesions detected from the patients’ CT or MRI images were negative or with low uptake in the PET images, and they were finally proved as benign. Conclusions. Comparing and matching metabolic images with anatomic images helped obtain a full understanding about the lesion and its peripheral structures. The fusion method was simple, practical and useful for localizing metabolically changed lesions.

CT MANIFESTATIONS IN PULMONARY ALVEOLAR PROTEINOSIS AND COMPARED WITH CHEST RADIOGRAPHY(REPORT OF SIX CASES)

The CT including HRCT appearances of six patients with histopathologically confirmed pulmonary alveolar proteinosis(PAP) were evaluated and compared with those of chest radiographs In all patients the CT manifestations were quite similar: bilateral and diffuse airspace consolidation was usually patchy or confluent with sharply defined margins, intermingled with normal lung tissue The configuration of lung lesions was “geographical” in outline with angulate, strait and curved margins There were white branching linear opacities within the ground glass background Although various pulmonary diseases may mimic PAP in some way, a full awareness of the characteristic CT appearances of PAP is helpful in achieving a correct diagnosis CT may provide more accurate evidence than chest radiograph for the evaluation of the extent and delineation of PAP

Numerical simulation of asphalt mixture based on three-dimensional heterogeneous specimen

In order to verify the validity of finite element numerical simulation method for asphalt mixture, which consists of aggregates, mastic （where mastic is a kind of fine mixture composed of asphalt binder mixed with fines and fine aggregates） and air voids, based on three-dimensional （3D） heterogeneous specimen, X-ray computerized tomography （X-ray CT） was used to scan the asphalt specimens to obtain the real internal microstrnctures of asphalt mixture. CT images were reconstructed to build up 3D digital specimen, and the viscoelastic properties of mastic were described with Burgers model The uniaxial creep numerical simulations of three different levels of aggregate gradation were conducted. The simulation results agree well with the experimental results. The numerical simulation of asphalt mixture incorporated with real 3D microstructure based on finite element method is a promising application to conduct research of asphalt concrete. Additionally, this method can increase the mechanistic understanding of global viscoelastic properties of asphalt mixtures by linking the real 3D microstructure.

Nanoparticulate X-ray CT contrast agents

X-ray computed tomography(CT) has been widely used as a powerful diagnostic tool in clinics because it can provide high-resolution 3D tomography of the anatomic structure based on the distinctive X-ray absorptions between different tissues. Currently, CT contrast agents are mainly small iodinated molecules, which suffer from drawbacks such as short blood- retention time, nonspecific in vivo biodistribution, and renal toxicity. Utilization of nanoparticles as potential CT contrast agents to overcome the aforementioned issues has advanced rapidly. In this mini review, we introduce current research efforts in the development of nanoparticulate CT contrast agents and discuss the challenges for additional breakthroughs in this field.

An experimental investigation of failure mechanical behavior in cylindrical granite specimens containing two non-coplanar open fissures under different confining pressures

Fissures play a significant role in predicting the unstable failure of rock mass engineering.For deep rock underground engineering,rock mass containing pre-existing fissures is usually located in triaxial stress state.Therefore,not only pre-existing fissure but also confining pressure affects the failure mechanical behavior of rock material.In this research,the granite specimens containing two non-coplanar open fissures were investigated by a series of conventional triaxial compression tests.First,the effect of bridge angle and confining pressure on strength and deformation characteristics of granite specimens was evaluated.Results show that the triaxial compressive strength,failure axial strain,and crack damage threshold increased nonlinearly with confining pressure.Under high confining pressures,elastic modulus was insensitive to bridge angle.Then,an X-ray micro-CT scanning technique was used to analyze the internal fracture characteristics of granite specimens with respect to various bridge angles and confining pressures.Five typical crack coalescence modes were identified,namely,indirect coalescence,shear coalescence and three types of tensile coalescence.The reconstructed 3-D CT images indicated that under uniaxial or low confining pressures,the bridge angle had a significant effect on crack evolution behavior,while under high confining pressures,shear-dominated failures occurred with the development of anti-wing cracks.

A new solid-conversion gas detector for high energy X-ray industrial computed tomography

A new type of solid-conversion gas detector is investigated for high energy X-ray industrial computed tomography (HECT). The conversion efficiency is calculated by using the EGSnrc Monte Carlo code on the Linux platform to simulate the transport process of photons and electrons in the detector. The simulation results show that the conversion efficiency could be more than 65%, if the X-ray beam width is less than about 0.2 mm, and a tungsten slab with 0.2 mm thickness and 30 mm length is employed as a radiation conversion medium. Meanwhile the results indicate that this new detector has higher conversion efficiency as well as less volume. Theoretically this new kind of detector could take place of the traditional scintillation detector for HECT.

The radiological image of pulmonary inflammatory pseudotumor:an analysis of 36 cases

Objective:The aim of the study was to discuss the X-ray and CT manifestations and characteristics of pulmonary inflammatory pseudotumors.Methods:The 36 patients with pathological diagnosis of pulmonary inflammatory pseudotumor were tested by thoracic X-ray and CT scan,and their imaging characteristics were analyzed.Results:Most of masses had intact capsule and smooth border.It was very important to diagnose pulmonary inflammatory pseudotumor when the mass was closed to or adhered to the pleura with irregular shadow or being sharply circumscribed.Conclusion:X-ray and CT scan are very important ways to diagnose the pulmonary inflammatory pseudotumor,and to accurately diagnose it,the clinical data,complete analysis are also necessary.

Classification of Medical Brain Images

Since brain tumors endanger people’s living quality and even their lives, the accuracy of classification becomes more important. Conventional classifying techniques are used to deal with those datasets with characters and numbers. It is difficult, however, to apply them to datasets that include brain images and medical history (alphanumeric data), especially to guarantee the accuracy. For these datasets, this paper combines the knowledge of medical field and improves the traditional decision tree. The new classification algorithm with the direction of the medical knowledge not only adds the interaction with the doctors, but also enhances the quality of classification. The algorithm has been used on real brain CT images and a precious rule has been gained from the experiments. This paper shows that the algorithm works well for real CT data.

PAA-capped GdF3 nanoplates as dual-mode MRI and CT contrast agents

Aiming at improving the sensitivity and accu- racy 9f diagnosis, the combination of magnetic resonance imaging （MRI） and X-ray computed tomography （CT） in a single probe is in urgent need. Here, we report the devel- opment of polyacrylic acid （PAA）-capped GdF3 nanoplates （NPs） as novel MRI and CT dual-mode contrast agents （CAs） with high longitudinal relaxivity （rl） and large X-ray attenuation coefficient. Uniform GdF3 rhombic NPs were fabricated by controlling reaction conditions and intro- ducing dopants. The average size of GdF3 NPs is （10.6 ：k 1.1） nm in long diagonal, （7.0 -t- 0.8） nm in short diagonal, and （4.2 -4- 1.2） nm in thickness. Ligand-exchange treat- ment was performed to render the NPs water-dispersible. The rl of PAA-capped GdF3 NPs （15.8 L/（mmol s）） is four times higher than that of clinically used Gd-DTPA. We suppose that the high r~ value originates from the con- struction of two-dimensional （2D） nanostructures, which endows nanocrystals with larger surface areas and longer rotational correlation time than those of sphere nanostruc- tures with the same volume. The CT contrast enhancement ability of PAA-capped GdF3 NPs was evaluated in com- parison with clinically used Iohexol. The above results suggest that the PAA-capped GdF3 NPs could serve as CAs for MRI and CT dual-mode imaging.