电阻抗图象重建的新正则化方法

Image reconstruction in elecrical impedance tomography(EIT)is a highly ill-posed inverse problem,Regularization techniques must be used in order to solve the problem,In this paper,a new regularization method based on the spatial filtering theory is proposed.The new regularized reconstruction for EIT is independent of the estimation of impedance distribution,so it can be implemented more easily than the maxiumum a posteriori(MAP) method.The regularization level in our proposed method varies spatially so as to be suited to the correlation character of the object‘s impedance distribution.We implemented our regularization method with two dimensional computer simulations.The experimental results indicate that the quality of the reconstructed impedance images with the descibed regularization method based on spatial filtering theory is better than that with Tikhonov method.     

三维锥束CT迭代重建算法对比研究

在计算机断层成像（CT）中,代数重建算法（ART）、联合代数迭代重建算法（SART）、有序子集期望值最大重建算法（OSEM）是迭代重建技术中广泛应用的3种技术,文章针对三维锥束CT情况,比较研究了上述3种迭代算法在含噪投影数据、完备投影数据以及投影数据稀疏和视角受限情况下的重建结果,并对重建结果进行了对比和分析。仿真结果表明：在一定条件下,OSEM算法重建的图像质量好于其他两种算法。     

牙颌组织CT图像处理技术研究

为了建立牙颌组织的三维有限元模型,必须取得牙颌组织的轮廓形态数据。本文提出了一种通过对牙颌组织的CT图像进行处理,从而取得牙颌组织的轮廓形态数据的方法。     

Computed tomography angiography-guided percutaneous coronary intervention in chronic total occlusion

Objective:The aim of this study is to investigate if dual-source computed tomography(DSCT) could guide the percutaneous coronary intervention(PCI) of chronic total occlusion(CTO).Methods:We enrolled patients who were confirmed to have at least one native coronary artery CTO by DSCT before they underwent selective PCI in the period from December 2007 to October 2008.A CTO was defined as an obstruction of a native coronary artery with no luminal continuity.The CT-guided PCI procedure involved placing CT and fluoroscopic images side-by-side on the screen.DSCT images were analyzed for location,segment,plaque characteristics,calcification,and proximal lumen diameter of the CTO before PCI.The guidewire was advanced and manipulated under CT guidance.The PCI was carried out and the results were compared.Results:Seventy-four CTOs were assessed.PCI was successful in 57 cases of CTOs(77.0%).According to the results,CTOs were divided into two groups:successful-PCI and failed-PCI.All coronary artery paths of CTOs were clearly recognized by DSCT.In the successful-PCI group,soft plaques were detected much more often than those in the failed-PCI group,but fibrous and calcified plaques were seen more often in the failed-PCI group.Calcification severity in CTO segments showed a significant difference between the groups(P=0.014).Calcified plaques were detected in 20(35.1%) lesions in the successful-PCI group.More than 70% of the failures were calcified plaques,of which there were two arc-calcified and one circular-calcified lesions.Occlusions were longer in the failed-PCI group than those in the successful-PCI group [(38.8±25.0) vs.(18.0±15.3) mm,respectively,P0.01].Fewer guidewires were used in the successful-PCI group compared with the failed-PCI group(1.7±1.0 vs.2.5±0.9,respectively,P0.01).The logistic regression analysis indicated that predictors of recanalization of CTOs included occlusion length(P=0.0035,risk ratio(RR)=0.93) and calcification severity(P=0.05,RR=0.27).Multi-linear trends analysis showed that the factors affecting procedural time were CTO location(P=0.0141) and occlusion length(P=0.0035).Conclusions:DSCT could delineate the path of CTOs and characterize plaques.The outcomes of PCI were related to thrombolysis in myocardial infarction(TIMI) flow grade,CTO characteristics,severity of calcified plaques,and the length of occlusive segments.Occlusion length and calcification severity were independent predictors of CTOs.Occlusion length and CTO segments could also help to estimate the duration of interventional procedures.     

基于改进的有序子集的SAGE算法在PET图像重建中的应用

提出了一种利用修改的有序子集(MOS)方法改进空间交替广义期望最大(SAGE)算法收敛性的方法.新的可变有序子集算法(MOS-SAGE)通过修改投影数据的数目和子集的排列循序加速收敛速度.其中每一个子集中的投影数目按2,4,8,16,32,64来排列以便重建算法首先恢复高频部分信息,然后重建低频部分信息.另外新算法还使相邻子集尽可能分离以减少投影间的相关性,达到加速收敛的效果.实验中,运用MOS-SAGE算法对计算机仿真的PET投影数据和实际的临床数据进行重建.几种误差分析结果表明,MOS-SAGE算法的收敛性能比SAGE算法和有序子集期望最大算法(OSEM)要快,重建后的图像更接近仿真用的模板图像.     

基于可调子块迭代的加速SAGE算法在PET图像重建中的应用

提出了一种可调子块迭代(RBI)方法加速空间交替广义期望最大(SAGE)算法的收敛性.新的可调子块迭代的空间交替广义期望最大算法(RBI-SAGE)组合了RBI算法和SAGE算法的优点用于加速正电子发射断层(PET)图像重建.RBI-SAGE将投影数据分成不连续的子块,每一次迭代仅包含一个这样的子块.在每一个子块中用SAGE算法序列更新参数.实验中,运用RBI-SAGE算法与SAGE算法对PET图像进行重建.结果表明,RBI-SAGE收敛性能比SAGE算法优越,且重建图像质量较高.     

A Bayesian PET reconstruction method using segmented anatomical membrane as priors

In this paper a fully Bayesian PET, reconstruction method is presented for combining a segmented anatomical membrane a priori. The prior distributions are based on the fact that the radiopharmaceutical activity is similar throughout each region and the anatomical information is obtained from other imaging modalities such as CT or MRI. The prior parameters in prior distribution are considered, drawn from hyperpriors for fully Bayesian reconstruction. Dynamic Markov chain Monte chain Monte Carlo methods are used on the Hoffman brain phantom to gain estimates of the posterior mean. The reconstruction result is compared to those obtained by ML, MAP. Our results showed that the segmented anatomical membrane a priori exhibit improved the noise and resolution properties. Project supported by NSFC of China (No. 69872034) and Zhejiang Provincial Natural Science Foundation.     

基于多级BP神经网络的EIT阻抗变化位置的确定

Electrical impedance tomography (EIT) is a new computer tomography technology, which reconstructs an impedance (resistivity, conductivity) distribution, or change of impedance, by making voltage and current measurements on the object's periphery. Image reconstruction in EIT is an ill-posed, non-linear inverse problem. A method for finding the place of impedance change in EIT is proposed in this paper, in which a multilevel BP neural network (MBPNN) is used to express the non-linear relation between the     

利用自适应网格细分法的电阻抗成像

1 Introduction Electrical i mpedance tomography (EIT) is a non-in-vasive i maging technique with widespread applicationsin medicine and industry[1 ,2].In EITthe electric cur-rent is injected between all possible pairs of adjacentelectrodes , and voltage is measured among all otherelectrodes and a voltage reference electrode .Based onthese boundary measurements ,the internal resistivity(or conductivity) distribution of the body can be esti-mated using the boundary voltage based on various re-…     

完备伪Zernike矩相似不变量集的构造

为了解决传统方法构造的矩不变量特征集存在的完备性和独立性问题,提出了一种完备的伪Zemike矩相似变换(旋转、平移和缩放)不变量集的构造方法,并给出了系统的推导和证明.首先推导了几何变换前后图像的伪Zemike矩之间的关系,然后基于该关系得到了伪Zernike矩的相似不变量集,并将其表示成变换前图像的同阶和低阶伪Zer...     

Establishment of reference mandibular plane for anterior alveolar morphology evaluation using cone beam computed tomography

To propose a method of establishing the reference mandibular plane (MP), which could be reestablished according to the coordinates of the reference points, and then facilitate the assessment of anterior alveolar morphology using cone beam computed tomography (CBCT), sixty patients with bimaxillary protrusion were randomly selected and CBCT scans were taken. The CBCT scans were transferred to Materialism’s interactive medical image control system 10.01 (MIMICS 10.01), and three dimensional models of the entire jaws were constructed. Reference points determining the reference MP were positioned in the coronal, axial, sagittal windows, and the points were exactly located by recording their coordinates in the interfaces of software. The reference MP provided high intra-observer reliability (Pearson’s r 0.992 to 0.999), and inter-observer reliability (intra-class correlation coefficients (ICCs) 0.996 to 0.999).     

Lung ventilation functional monitoring based on electrical impedance tomography

Medically,electrical impedance tomography(EIT)is a relatively inexpensive,safe,non-invasive and portable technique compared with computerized tomography(CT)and magnetic resonance imaging(MRI).In this paper,EIT_TJU_Ⅱ system is developed including both the data collection system and image reconstruction algorithm.The testing approach of the system performance,including spatial resolution and sensitivity,is described through brine tank experiments.The images of the thorax physical model verify that the system can reconstruct the interior resistivity distribution.Finally,the lung ventilation functional monitoring in vivo is realized by EIT,and the visualized images indicate that the configuration and performance of EIT_TJU_Ⅱ system are feasible and EIT is a promising technique in clinical monitoring application.     

A pilot study on diagnosis of coronary artery disease using computed tomography first-pass myocardial perfusion imaging at rest

Background  

Although computed tomography coronary angiography (CTCA) can identify coronary stenosis, little data exists on the ability of multislice computed tomography (MSCT) to detect myocardial perfusion defects at rest.     

Segmental radiofrequency ablation of pulmonary vein ostia for patients with refractory paroxysmal atrial fibrillation using multi-slice spiral computed tomography guidance

INTRODUCTION Pulmonary veins(PV)may play an importantrole in both the initiation and maintenance of parox-ysmal atrial fibrillation(AF)(Fynn and Kalman,2004).Curative treatment of patients with paroxys-mal AF is possible by radiofrequency ablation,mak-ing segmental or linear lesions around the ostia ofPVs using a3-dimentional mapping system(Carto)(Pappone et al.,2000;2001;Oral et al.,2003).Multi-slice spiral computed tomography(MSCT)could generate a3-dimentional image of left atrium…     

Time series of EIT measurements and images during lung ventilation based on principal component analysis

The aim of this paper is to propose a useful method for exploring regional ventilation and perfusion in the chest and also separation of pulmonary and cardiac changes.The approach is based on estimating both electrical impedance tomography(EIT) measurements and reconstructed images by means of principal component analysis(PCA).In the experiments in vivo,43 cycles of heart-beat rhythm could be detected by PCA when the volunteer held breath;9 breathing cycles and 50 heart-beat cycles could be detected by PCA ...     

Voidage measurement based on genetic algorithm and electrical capacitance tomography

INTRODUCTION Two-phase flow exists widely in chemical, pe- troleum and metallurgical industries. The voidage is one of the most important parameters of two-phase flow because the measurement of the voidage is im- portant for safety, environmental protection, energy conservation and quality assurance in industry (Hewitt, 1978; Lin, 1992). Although many voidage measurement methods have been proposed, it is still difficult to measure the voidage due to the complexity of the characteristics o…     

A novel technique of three-dimensional reconstruction segmentation and analysis for sliced images of biological tissues

INTRODUCTION The past decades witnessed unprecedented ad-vances in the imaging science fields(Yelbuz et al.,2002;Campagnola et al.,2002;Sharpe et al.,2002).The technique of3D image reconstruction andanalysis plays a significant role in the basic researchof life science,which developed from2D imageprocessing but provides more information than2Dimage,and has rapidly expanded to molecular andcellular field(Guo et al.,1995;Trehan et al.,2003).Despite the rapid development of the new field,…     

Strengths and Weaknesses of Non-enhanced and Contrast-enhanced Cadaver Computed Tomography Scans in the Teaching of Gross Anatomy in an Integrated Curriculum

Cadaver-specific postmortem computed tomography (PMCT) has become an integral part in anatomy teaching at several universities. Recently, the feasibility of contrast-enhanced (CE)-PMCT has been demonstrated. The purpose of this study was to identify particular strengths and weaknesses of both non-enhanced and contrast-enhanced PMCT compared to conventional cadaver dissection. First, the students’ perception of the learning effectiveness of the three different modalities have been assessed using a 34-item survey (five-point Likert scale) covering all anatomy course modules. Results were compared using the nonparametric Friedman Test. Second, the most frequent artifacts in cadaver CT scans, were systematically analyzed in 122 PMCT and 31 CE-PMCT data sets to quantify method-related limitations and characteristics. Perfusion quality was assessed in 57 vascular segments (38 arterial and 19 venous). The survey was answered by n = 257/320 (80.3%) students. Increased learning benefits of PMCT/ CE-PMCT compared to cadaver dissection were found in osteology (2/3 categories, P < 0.001), head and neck (2/5 categories, P < 0.01), and brain anatomy (3/3 categories, P < 0.01). Contrast-enhanced-PMCT was perceived particularly useful in learning vascular anatomy (10/10 categories, P < 0.01). Cadaver dissection received significantly higher scores compared to PMCT and CE-PMCT in all categories of the abdomen and thorax (7/7 categories, P < 0.001), as well as the majority of muscular anatomy (5/6 categories, P < 0.001). Frequent postmortem artifacts (total n = 28, native-phase n = 21, contrast injection-related n = 7) were identified and assessed. The results of this work contribute to the understanding of the value of integrating cadaver-specific PMCT in anatomy teaching.     

Cone Beam Computed Tomography (CBCT) Technology and Learning Outcomes in Dental Anatomy Education: E-Learning Approach

E-learning is an educational method that improves knowledge innovation by sharing relevant images for advanced learning, especially in a pandemic state. Furthermore, cone-beam computed tomography (CBCT) is a method that gathers medical or dental diagnostic images. This study aimed to analyze the effectiveness of dental anatomy education through a CBCT technology tool, through teachers' and students' perspectives, adjusted according to the disruptions caused by the Covid-19 pandemic. A cohort study and longitudinal exploratory analysis were performed. Forty undergraduate first-year dental students, from the University of Coimbra in Portugal, were selected as per the inclusion and exclusion criteria. Two different teaching methods were applied during an identical time-period: face-to-face lectures complemented by physical models (T1 cohort) and webinar lectures complemented by CBCT images (T2 cohort). Learning outcomes were then studied according to theoretical and spatial orientation contexts. A self-reported survey that focused on students' satisfaction, stress, and support was studied. Both teaching methods were analyzed with paired sample student's t-test and Pearson Correlation Confidence intervals 95% with P < 0.05. Furthermore, exploratory factor analysis (EFA) was used for self-reported satisfaction survey validity and reliability analysis. The learning outcomes between T1 and T2 cohorts were statistically significant, (P < 0.001) corresponding to differences with a large effect degree (r > 0.60). Students' satisfaction, as measured on a six-point Likert scale, was positively influenced by the webinar lectures supplemented with CBCT images (T2 cohort) in a learning context (4.95 ± 0.5) and future applications (5.92 ± 0.27). In conclusion, the webinar approach with CBCT images was more effective and better learning method for teaching dental anatomy.     

光学PT扇束结构权重系数矩阵计算与实现

权重系数矩阵是光学过程层析成像(optical process tomography，简称光学PT)技术中非常重要的参数之一，它的传统计算是基于人工测算，其缺点是烦琐、且极其耗时。因此，本文利用Visual C 语言实现了光学过程层析成像系统扇束阵列传感器结构权重系数矩阵的即时计算。为光学敏感场灵敏度分布的计算、图像重建仿真以及光学PT系统的实现节省了时间，缩短了研究周期。