SPECT骨断层重建的滤波反投影法和有序最大期望值法的比较

目的:比较SPECT骨断层图像重建的有序最大期望值法(OSEM)与滤波反投影法(FBP)的图像效果。方法:32例患者进行SPECT骨断层显像,采集部位以脊柱为主。给药(30mCi99mTc-MDP)3～4h后进行断层图像采集。由1位技师对图像数据分别进行OSEM和FBP(包括Metz窗函数和Butterworth窗函数)图像重建。由3位核医学医师独立双盲阅片。结果:OSEM放射条纹状伪影远远少于FBP,图像分辨率和图像清晰度也优于FBP。结论:骨断层重建方法OSEM法优于FBP法。

Accelerating SAGE algorithm in PET image reconstruction by rescaled block-iterative method

A new method to accelerate the convergent rate of the space-alternatinggeneralized expectation-maximization (SAGE) algorithm is proposed. The new rescaled block-iterativeSAGE (RBI-SAGE) algorithm combines the RBI algorithm with the SAGE algorithm for PET imagereconstruction. In the new approach, the projection data is partitioned into disjoint blocks; eachiteration step involves only one of these blocks. SAGE updates the parameters sequentially in eachblock. In experiments, the RBI-SAGE algorithm and classical SAGE algorithm are compared in theapplication on positron emission tomography (PET) image reconstruction. Simulation results show thatRBI-SAGE has better performance than SAGE in both convergence and image quality.

FITTING CORRECTION METHOD OF RING ARTIFACTS FOR RECONSTRUCTING CONE-BEAM CT IMAGES

In high-resolution cone-beam computed tomography （CBCT） using the flat-panel detector, imperfect or defect detector elements cause ring artifacts due to the none-uniformity of their X-ray response. They often disturb the image quality. A dedicated fitting correction method for high-resolution micro-CT is presented. The method converts each elementary X-ray response curve to an average one, and eliminates response inconsistency among pixels. Other factors of the method are discussed, such as the correction factor variability by different sampling frames and nonlinear factors over the whole spectrum. Results show that the noise and artifacts are both reduced in reconstructed images

Investigation of prior image constrained compressed sensing-based spectral X-ray CT image reconstruction

To improve spectral X-ray CT reconstructed image quality, the energy-weighted reconstructed image xbins^W and the separable paraboloidal surrogates（SPS） algorithm are proposed for the prior image constrained compressed sensing（PICCS）-based spectral X-ray CT image reconstruction. The PICCS-based image reconstruction takes advantage of the compressed sensing theory, a prior image and an optimization algorithm to improve the image quality of CT reconstructions.To evaluate the performance of the proposed method, three optimization algorithms and three prior images are employed and compared in terms of reconstruction accuracy and noise characteristics of the reconstructed images in each energy bin.The experimental simulation results show that the image xbins^W is the best as the prior image in general with respect to the three optimization algorithms; and the SPS algorithm offers the best performance for the simulated phantom with respect to the three prior images. Compared with filtered back-projection（FBP）, the PICCS via the SPS algorithm and xbins^W as the prior image can offer the noise reduction in the reconstructed images up to 80. 46%, 82. 51%, 88. 08% in each energy bin,respectively. M eanwhile, the root-mean-squared error in each energy bin is decreased by 15. 02%, 18. 15%, 34. 11% and the correlation coefficient is increased by 9. 98%, 11. 38%,15. 94%, respectively.

Technique of Error Concealment for Block-Based Image Coding Using Genetic Algorithm

Since real world communication channels are not error free, the coded data transmitted on them may be corrupted, and block based image coding systems are vulnerable to transmission impairment. So the best neighborhood match method using genetic algorithm is used to conceal the error blocks. Experimental results show that the searching space can be greatly reduced by using genetic algorithm compared with exhaustive searching method, and good image quality is achieved. The peak signal noise ratios(PSNRs) of the restored images are increased greatly.

CT系统参数标定及成像研究

本文通过分析CT 系统工作原理及附件中各个参数的研究,在合理假设条件下,对数据进行处理,运用数学软件Matlab中的 radon 和iradon 等函数建立数学模型,在此过程中,我们运用了中心切片定理、傅里叶函数、直接滤波投影法、滤波反投影图像重建等方法对CT系统参数标定及成像进行分析和求解.针对问题一,有题目要求和研究分析可知,此题我们要根据题目所给数据重建原始图像,通过直接滤波投影法以及对特殊位置的分析进行相应的数学计算和位置匹配,可以得到旋转中心的位置.同样,观察水平或垂直特殊位置的数据可以得到180次旋转的方向.针对问题二,此介质形状是未知的,根据滤波反射投影法,中心切片定理等使用MATLAB中的iradon函数对附件3进行图像重建,得到灰度图像,可以确定该介质的几何形状,再经旋转计算,即可得到未知介质在正方形托盘中的位置图像.转换为旋转后的图像矩阵,即可得到图3对应位置的吸收率.

An ECT System Based on Improved RBF Network and Adaptive Wavelet Image Enhancement for Solid/Gas Two-phase Flow

Electrical capacitance tomography(ECT) is a non-invasive imaging technique that aims at visualizing the cross-sectional permittivity distribution and phase distribution of solid/gas two-phase flow based on the measured capacitance.To solve the nonlinear and ill-posed inverse problem:image reconstruction of ECT system,this paper proposed a new image reconstruction method based on improved radial basis function(RBF) neural network combined with adaptive wavelet image enhancement.Firstly,an improved RBF network was applied to establish the mapping model between the reconstruction image pixels and the capacitance values measured.Then,for better image quality,adaptive wavelet image enhancement technique was emphatically analyzed and studied,which belongs to a space-frequency analysis method and is suitable for image feature-enhanced.Through multi-level wavelet decomposition,edge points of the image produced from RBF network can be determined based on the neighborhood property of each sub-band;noise distribution in the space-frequency domain can be estimated based on statistical characteristics;after that a self-adaptive edge enhancement gain can be constructed.Finally,the image is reconstructed with adjusting wavelet coefficients.In this paper,a 12-electrode ECT system and a pneumatic conveying platform were built up to verify this image reconstruction algorithm.Experimental results demonstrated that adaptive wavelet image enhancement technique effectively implemented edge detection and image enhancement,and the improved RBF network and adaptive wavelet image enhancement hybrid algorithm greatly improved the quality of reconstructed image of solid/gas two-phase flow [pulverized coal(PC)/air].

Measurement of a Three－dimensional Gas Temperature Field with Holographic Interferometry

It is well known that optical tomography can accurately and quantitatively reconstruct the refractive index field of a transparent medium and display the three dimensional image of other physical quantities relevant to temperature or density. In this paper, a new multidirectional holographic interferometric system is built, and two kinds of image reconstruction algorithms are introduced and an automatic image processing system of interferogram is designed. A three dimentsional asymmetric gas flow field above a combustor is expertmentally investigated with holographic interferometry. The reconstructed temperatures are similar to those measured with a thermocouple.

Surgical simulation and evaluation in anterior cruciate ligament reconstruction with image-free navigation

A surgical simulation and evaluation method in the anterior cruciate ligament(ACL)reconstructionwith image-free navigation was presented.Firstly,video tracking module,bone surface reconstructionmodule and virtual simulation module of this system were discussed.Secondly,the coordinate relations ofseveral surgery objects(including surgical instrument,anatomical,camera and screen)in the surgicalenvironment,the tracking based on MicronTracker with two cameras and the bone surface real-time recon-struction based on the Delaunay algorithm were introduced in detail.Finally,experiments of anisometrymeasurement and virtual simulation on two plastics were carried out to verify the validity of the proposedmethod.The anisometry value of reconstructed ACL was 8.970039mm.The effectiveness of ACL recon-struction has been proved by preliminary evaluation trials.

Research on Novel Natural Image Reconstruction and Representation Algorithm based on Clustering and Modified Neural Network

In this paper, we conduct research on the novel natural image reconstruction and representation algorithm based on clustenng and modified neural network. Image resolution enhancement is one of the earliest researches of single image interpolation. Although the traditional interpolation and method for single image amplification is effect, but did not provide more useful information. Our method combines the neural network and the clustering approach. The experiment shows that our method performs well and satisfactory.

Two-Level Bregman Method for MRI Reconstruction with Graph Regularized Sparse Coding

In this paper, a two-level Bregman method is presented with graph regularized sparse coding for highly undersampled magnetic resonance image reconstruction. The graph regularized sparse coding is incorporated with the two-level Bregman iterative procedure which enforces the sampled data constraints in the outer level and updates dictionary and sparse representation in the inner level. Graph regularized sparse coding and simple dictionary updating applied in the inner minimization make the proposed algorithm converge with a relatively small number of iterations. Experimental results demonstrate that the proposed algorithm can consistently reconstruct both simulated MR images and real MR data efficiently, and outperforms the current state-of-the-art approaches in terms of visual comparisons and quantitative measures.

Measurement of Ice Movement in Water Using Electrical Capacitance Tomography

The permafrost with the highest altitude and largest area in the mid and low latitude is located in the Qinghad-Tibet Plateau. As most frozen soils contain ice particles which are very sensitive to temperature and other external parameters, thus influencing the stability of the embankment in permafrost regions, it is very important to develop techniques to prevent damages to railway embankments due to thaw settlement. In this paper, the electrical capacitance sensors are designed to study the freezing front movement in a vessel and ice movement in water, which is the first step to apply the ECT system to the study of frozen soil. Two sensor arrangements are put into use. First, the traditional closed electrode sensors are put into use. In this arrangement, the electrodes are attached to the outside of the pipe or vessel, and the cross-sectional distribution of ice and water could be reconstructed from the capacitances measured. Also, the ice moving track at the cross section could be reflected thoroughly.Since the traditional closed electrode sensors can not meet the needs of measuring the ice freezing front move- ment, a new electrode sensors structure, that is, the unclosed electrode sensors are designed to satisfy the specific test of frozen soil. In this arrangement, several pairs of electrodes are arranged along the height of the vessel. A sudden decrease in the measured capacitance is observed when the freezing front advances past the electrodes.Therefore, according to the capacitance variation, the ice movement can be reflected. In summary, electrical capacitance tomography has the advantages of being non-intrusive. With different electrode sensor arrangement, ice movement and ice freezing front can be obtained. The electrical capacitance sensor system can be applied to investigate the complicated phenomena in frozen soil.

A method for brain 3D surface reconstruction from MR images

Due to the encephalic tissues are highly irregular, three-dimensional （3D） modeling of brain always leads to compli- cated computing. In this paper, we explore an efficient method for brain surface reconstruction from magnetic reso- nance （MR） images of head, which is helpful to surgery planning and tumor localization. A heuristic algorithm is pro- posed foi＂ surface triangle mesh generation with preserved features, and the diagonal length is regarded as the heuristic information to optimize the shape of triangle. The experimental results show that our approach not only reduces the computational complexity, but also completes 3D visualization with good quality.

Colored 3D surface reconstruction using Kinect sensor

A colored 3D surface reconstruction method which effectively fuses the information of both depth and color image using Microsoft Kinect is proposed and demonstrated by experiment.Kinect depth images are processed with the improved joint-bilateral filter based on region segmentation which efficiently combines the depth and color data to improve its quality.The registered depth data are integrated to achieve a surface reconstruction through the colored truncated signed distance fields presented in this paper.Finally,the improved ray casting for rendering full colored surface is implemented to estimate color texture of the reconstruction object.Capturing the depth and color images of a toy car,the improved joint-bilateral filter based on region segmentation is used to improve the quality of depth images and the peak signal-to-noise ratio(PSNR)is approximately 4.57 d B,which is better than 1.16 d B of the joint-bilateral filter.The colored construction results of toy car demonstrate the suitability and ability of the proposed method.