检索结果-内蒙古大学图书馆

X-ray projection simulation based on physical imaging model

JOURNAL OF X-RAY SCIENCE AND TECHNOLOGY 2006年第3期14卷 177-189页

作者： Tang, Shaojie Yu, Hengyong Yan, Hao Bharkhada, Deepak Mou, Xuanqin Xi An Jiao Tong Univ Inst Image Proc & Pattern Recognit Xian 710049 Shaanxi Peoples R China Univ Iowa Dept Radiol CTMicro CT Lab Iowa City IA 52242 USA

In the X-ray CT research area, the linear integral projections of mathematical phantoms were extensively used to evaluate the proposed algorithms with a hypothesis of monochromatic model. However, X-ray tube emits a spectrum of energies and hence it becomes difficult to study some important aspects, such as the reconstructed density accuracy of special reconstruction algorithm and beam hardening effects of polychromatic imaging. If the energy spectrum of X-ray tube, geometry of phantom, and material compositions of all sub-regions are known, the actual projections can be simulated with more accuracy. Motivated by this fact, we propose an improved three-step discrete scheme to simulate the X-ray projections based on physical model. First, CT-numbers of all sub-regions of a phantom are determined in advance. Next, CT-numbers are decomposed into different material compositions under the constraint that sub-regions correspond to different human tissues. Finally, the projections are measured according to the energy spectrum distribution of X-ray tube, using the knowledge of X-ray imaging physics and our strategy to simulate the projecting process. Our scheme requires significantly less storage and computation to achieve a higher accuracy and precision. To demonstrate the feasibility of our scheme, we use the well-known FORBILD head phantom to generate projections and the feldkamp algorithm for image reconstruction. The anticipated beam hardening effects are clearly seen in images reconstructed from projections simulated using our scheme. This scheme can be utilized in many medical X-ray imaging research aspects, such as algorithm design, performance analysis, distortion calibrations, artifact reduction, etc.

关键词： X-ray projection physical imaging model energy spectrum material composition FORBILD phantom feldkamp algorithm

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3D IMAGE-RECONSTRUCTION USING CONE-BEAM TOMOGRAPHY

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NDT & E INTERNATIONAL 1994年第2期27卷 83-87页

作者： JAN, ML CHEN, CY YEH, CK YEH, TR WANG, MT ATOM ENERGY COUNCIL TAIPEITAIWAN

3D X-ray cone beam tomography for possible NDT application is illustrated via the feldkamp convolution backprojection reconstruction algorithm. Gauss and Ham filter functions are implemented in order to alleviate artifacts (streaks and ringing). In addition, the effect of cone vertex position error on image reconstruction is investigated. Finally, film based X-ray projection radiographs were scanned into the computer to reconstruct the 3D images and verify the performance of the software program.

关键词： IMAGE RECONSTRUCTION TOMOGRAPHY feldkamp algorithm

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Accurate and efficient image intensifier distortion correction algorithm and its application in volume tomographic angiography

Accurate and efficient image intensifier distortion correcti...

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Conference on the Physics of Medical Imaging, at the SPIE Medical Imaging 1997 Symposium

作者： Wang, XH Ning, RL Univ. of Rochester (United States)

ISBN: (纸本)0819424439

An algorithm has been developed to correct the image distortion introduced by the image intensifier - CCD camera chain in our volume tomographic angiography imaging system. First the distorted image is partitioned into small quadrilateral regions, then each partition is mapped individually to the corrected image by its corresponding bilinear functions. The parameters of these bilinear functions can be acquired by a special calibration procedure and stored as a lookup table. The maximum errors before and after the distortion correction were measured to be 5.96 mm and 0.03 mm. The method is further applied to the 3D image reconstruction of a simulated vascular phantom and live animal studies.

关键词： image intensifier pincushion distortion S-distortion finite element volume tomographic angiography feldkamp algorithm

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Measurement Methods and 3D Reconstruction algorithms of X ray CT Inspection

Measurement Methods and 3D Reconstruction Algorithms of X ra...

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Annual Conference of the SICE

作者： Tanemura, Mitsukuni Tanaka, Toshiyuki Kikuchi, Kazuo Keio Univ Dept Appl Phys & Phys Informat Tokyo 108 Japan Comscan Tecno Co LTD Yokohama Kanagawa Japan

ISBN: (纸本)9784907764302

X ray CT system is used for nondestructive inspection in industrial field. But there are some problems when we got the images of objects, namely rate of expansion, contrast and measurement area. This study aims at solving these problems by contriving oblique offset X ray CT system We improved feldkamp algorithm which is the conventional 3D reconstruction method. Supportive experimental results are provided based on simulation phantom data.

关键词： X ray computed tomography 3D reconstruction feldkamp algorithm Oblique scan Offset scan

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The method of high-accuracy 3D reconstruction for oblique X-ray CT images

The method of high-accuracy 3D reconstruction for oblique X-...

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Annual Conference on the Society-of-Instrument-and-Control-Engineers

作者： Yoshizawa, Satoshi Tanaka, Toshiyuki Kikuchi, Kazoo Keio Univ Dept Appl Phys & Phys Informat Tokyo 108 Japan Comscan Tecno Co Ltd Tokyo Japan

ISBN: (纸本)9784907764289

X-ray CT system for industrial inspection has some problems when it inspects flat objects. The problems are expansion rate and contrast. We previously implemented an oblique X-ray CT system, and found those problems were almost solved and that vertical accuracy was comparatively low. We now intend to improve the vertical accuracy by implementing extra two-are cone-beam X-ray scan. The two-arc scan is for compensating the lack of data from the conventional oblique scan. The overall reconstruction algorithm is based on inverse Radon transform and Grangeat's formula. In order to evaluate the accuracy of reconstructed images quantitatively, the computer simulation using a BGA phantom was implemented. Through the study it was revealed that the proposed method can compensate the previous reconstruction accuracy, and that proper distribution from both oblique scan and two-arc scan is needed for the correct reconstruction.

关键词： X ray computed tomography oblique CT 3D reconstruction feldkamp algorithm Grangeat's algorithm

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Cone-beam X-ray tomography using continuous wavelet transformation

Cone-beam X-ray tomography using continuous wavelet transfor...

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Conference on Wavelet Applications in Signal and Image Processing VIII

作者： Zhao, SY Wang, G Univ Missouri Dept Math & Comp Sci St Louis MO 63130 USA

ISBN: (纸本)0819437646

Recently, medical computed tomography (CT) began a transition from fan-beam to cone-beam geometry with the introduction of multi-row-detector systems. Therefore, cone-beam techniques become important for medical CT. Despite recent advances, the approximate reconstruction method of feldkamp remains the most commonly employed cone-beam reconstruction algorithm because of its computational efficiency and clinical applicability. Unfortunately, the derivation of the feldkamp cone-beam reconstruction formula is based on geometric tilted fan heuristic. In this paper, we give a wavelet derivation of the feldkamp cone-beam reconstruction method. It is found that the feldkamp algorithm is an outcome of a zero-order approximation to the longitudinal wavelet decomposition of the object function to be reconstructed. Since the approximation is explicitly given, error estimates can be derived analytically. Theoretically, it also arises the possibility of improvement of the feldkamp cone-beam algorithm.

关键词： continuous wavelet transformation X-ray computed tomography (CT) cone-beam geometry feldkamp algorithm three-dimensional reconstruction

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3D reconstruction of x ray CT image for nondestructive inspection

3D reconstruction of x ray CT image for nondestructive inspe...

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SICE-ICASE International Joint Conference

作者： Yoshizawa, Satoshi Tanaka, Toshiyuki Kikuchi, Kazuo Keio Univ Dept Appl Phys & Phys Informat Tokyo Japan Comscan Tecno Co Ltd Tokyo Japan

ISBN: (纸本)9788995003848

X ray CT system is used for nondestructive inspection in industrial field. There are some problems when we get the images of flat objects, namely rate of expansion and contrast. This study aims at solving these problems by contriving inclined X ray CT system. We improved feldkamp algorithm, which is the conventional 3D reconstruction method and applied it to the data gained by inclined system. In order to evaluate the accuracy of reconstructed images quantitatively, the computer simulation using a Shepp-Logan phantom was implemented. Through the study the proposed method for the reconstruction of three-dimensional CT images was successfully implemented. Further improvement of image accuracy can still be done to get more clear and accurate CT images.

关键词： X ray computed tomography inclined CT 3D reconstruction feldkamp algorithm

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Parallel Implementation for Cone Beam based 3D Computed Tomography (CT) Medical Image Reconstruction on Multi-core Processors

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World Congress on Medical Physics and Biomedical Engineering

作者： Chu, Chang-Yuan Chen, Szi-Wen Chang Gung Univ Dept Electron Kwei Shan Tao Yuan Taiwan

ISBN: (纸本)9783642038815

3D or multi-dimensional medical image reconstruction is attracting more and more attention in modern era. Rapid volumetric image reconstruction is of paramount importance to clinicians for prompt diagnosis and analysis of complex tissue alternations. However, due to a high demand on computation for either the analytical or iterative image reconstruction algorithms, it is almost impossible to meet the requirement of real-time reconstruction. On the other hand, with high computing capability and broad banding characteristic, recently multi-core processors provide a new possibility and hopeful start for some of the most computation-demanding application such as medical imaging, digital media and entertainment equipment. This study aims to parallelize an analytical 3D CT image reconstruction algorithm, the so-called FDK method and to implement it on an existing multi- core platform system, towards a real- time 3D medical image reconstruction algorithm, the coding optimizations and a comparative results of run time savings are described.

关键词： Program parallelism Computer Tomography (CT) Conebeam feldkamp algorithm Multi-core

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Simulation of cone beam computed tomography chest imaging with parallel computing: Nodule detectability versus dose

Simulation of cone beam computed tomography chest imaging wi...

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Medical Imaging 2005 Conference

作者： Tu, SJ Shaw, CC Chen, LY Univ Texas MD Anderson Canc Ctr Dept Imaging Phys Houston TX 77030 USA

ISBN: (纸本)0819457191

We have developed a computer simulation model for cone beam computed tomography (CT) chest imaging on a general-purpose personal computer cluster system. Our simulation model incorporates quantum noise, detector blurring, and additive system noise. The main objective is to study how x-ray dose would affect the detectability of nodules in simulated cone beam CT chest images. The Radon transforms formalism was used to calculate the projection views for an analytically modeled chest phantom. A parallel random number generator was then used to simulate and add quantum noise whose level depends on the incident x-ray fluence, detector quantum efficiency and pixel size (0.4 mm). We also simulated detector blurring by convolving the noise added images with a Gaussian function matching the modulation transfer function measured for the flat panel x-ray detector studied. Then we modeled the additive system noise and added to the final projection images. The noise level (sigma = 20) for the additive system noise was calculated from the noise power spectrum of the flat panel detector using the curve-fitting technique. The feldkamp algorithm with a Gaussian pre-filtering process was used to reconstruct 3D image data from the projection images. For nodule contrast, the linear attenuation coefficient difference between nodule and lung was set to 10.0%. The diameters for the spherical nodules ranged from 0.2 to 1.7 cm. It was found that our Gaussian pre-filtering process helped reduce the noise level in the reconstructed images and allowed the nodules to be better visualized significantly. At 100, 000 photons per pixel (8000 mR total un-attenuated exposure at the rotating center), nodules 0.3 mm or larger could be visualized;at 101 000 photons per pixel (800 mR), nodules 0.5 mm or larger could be visualized: at 2000 photons per pixel (160 mR), only nodules 1.5 mm or larger could be visualized.

关键词： cone beam CT feldkamp algorithm parallel computing noise simulation detector blurring flat panel x-ray detector parallel random number generator nodule detection quantum noise and additive system noise

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Measurement methods and 3D reconstruction algorithms of X ray CT inspection

Measurement methods and 3D reconstruction algorithms of X ra...

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SICE Annual Conference

作者： Mitsukuni Tanemura Toshiyuki Tanaka Kazuo Kikuchi Department of Applied Physics and Physico Informatics Keio University Japan Comscan Tecno Company Limited Japan

ISBN: (纸本)9784907764296

X-ray CT system is used for nondestructive inspection in industrial field. But there are some problems when we get the images of objects, namely rate of expansion, contrast and measurement area. This study aims at solving these problems by contriving oblique offset X-ray CT system. We improved feldkamp algorithm which is the conventional 3D reconstruction method. Supportive experimental results are provided based on simulation phantom data.

关键词： X ray computed tomography 3D reconstruction feldkamp algorithm Oblique scan Offset scan

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