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Study on Artifact occurredin the X-ray CT Image due to the Motion of the Object

X射线CT图像因物体运动而产生伪影的研究

基本信息

批准号：
05452408
负责人：
SATO Shunsuke
金额：
$ 2.94万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05452408/
关键词：
Motion of the Object X-ray CT Cycloid Compton Scattering X-ray CT Collimators Energy Window S N Water Phantom 水球ファントム平行投影点源モーションアーチファクト

项目摘要

(1) In the X ray computed tomography (CT), time to scan an object must be allowed to obtain its projection data. If the object is not steady during the scanning, itsu reconstructed image would contain errors called "mottifacts. Recently , two kinds of motion artifact,"blurred image" and "stroboscopic image" , have been found in clinical experience, and their theoretical analyzes have been demanded. Assuming that an object is a rigid body, its motion can be divided into rotary and parallel motions. This paper analyzes the degradiation of reconstructed images and artifacts due to the rotary motion of a rigid object. The degradiation of a CT image caused by rotation of an arbitrarily shaped rigid object is formulated by using a point-spread function. The cjaracteristics of blurred images of a rigid object due to its rotation in a CT and the shape of stroboscopic images also are analyzed. The cause of storoboscopic images is explained by using line source. The theories have been confirmed … More by computer simulation.(2) Compton scattering imaging can demonstrate the electron density of a given object which could be important for medical diagnosis. However, clinical application of the technique has not yet been developed, bacause a clear image can not be obtained for several reasons. The image is seriously contaminated by multiple scattering which is inevitable with Compton scattering. The electron density in a small region of the object is not obtained correctly unless multiple scattering is handled carefully. In the present paper, methods to eliminate multiple scattering in Compton scattering imaging system are discussed. A general purpose Monte Carlo code called EGS4 was used to simulate the processes of an incident photon interacting with a substance inside an object. Simulations were performed using a water sphere phantom with a radius of 10 cm irradiated by a beam of monochromatic X-rays at 100 keV.Scattered photons emitted from the phantom were observed and the ratio of the amount of single Compton scattering from a focal point to that of multiple scatterong was calculated. To improve the image quality, elimination of multiple scattering in Compton scattering is indispensable. To this end , theta and phi-collimators and an energy window were proposed and their effects were estimated quantitatively by simulations. It was shown that by introducing of the proposed methods in the imaging system, the ratio of the Compton scattering signal to the multiple scattering noise, S/N,could be improved from 0.022 to 40. Quantitative results derived from the simulations may be useful for the design of a pratical Compton scattering imaging system. Less

(1)在X射线计算机断层扫描(CT)中，必须留出扫描物体的时间以获得其投影数据。如果物体在扫描过程中不稳定，则重建图像会出现称为“模态”的错误。最近，临床经验中发现了“模糊图像”和“频闪图像”两种运动伪影，需要对其进行理论分析。假设物体是刚体，其运动可分为旋转运动和平行运动。本文分析了运动伪影的退化问题。由于刚性物体的旋转运动而重建的图像和伪影。由任意形状的刚性物体的旋转引起的 CT 图像的退化通过使用点扩散函数来表达。还分析了刚体在CT中由于旋转而产生的模糊图像的特点以及频闪图像的形状。用线光源解释了频闪图像的成因。的理论已通过计算机模拟得到证实。(2) 康普顿散射成像可以演示给定物体的电子密度，这对于医学诊断可能很重要。然而，由于多种原因无法获得清晰的图像，该技术尚未发展到临床应用。图像受到多重散射的严重污染，这是康普顿散射不可避免的。除非多次散射，否则无法正确获得物体小区域内的电子密度小心处理。本文讨论了康普顿散射成像系统中消除多重散射的方法。称为 EGS4 的通用蒙特卡罗代码用于模拟入射光子与物体内物质相互作用的过程。使用半径为 10 cm 的水球体模型进行模拟，并用 100 keV 的单色 X 射线束照射。从模型发射的散射光子为观察并计算来自焦点的单次康普顿散射量与多重散射量的比率。为了提高图像质量，消除康普顿散射中的多重散射是必不可少的。为此，提出了 theta 和 phi 准直器以及能量窗口，并通过模拟定量估计了它们的影响。结果表明，通过在成像系统中引入所提出的方法，康普顿散射信号的比率多重散射噪声的信噪比可以从 0.022 提高到 40。模拟得出的定量结果可能有助于设计实用的康普顿散射成像系统。少