口腔CT金属伪影与CT值校正研究与实现

发布时间：2018-03-19 21:35

  本文选题：口腔CT　切入点：金属伪影　出处：《东北大学》2013年硕士论文　论文类型：学位论文

【摘要】：目前,口腔CT在齿科疾病的检查中发挥着越来越重要的作用,它通过测量X射线在各个方向上透过人体断层时的累积衰减系数(或称投影),由计算机重建得到整个横断面上X射线衰减系数的分布,从而帮助医生诊断病灶部位。口腔CT相比全身CT具有剂量小、空间分辨率高等优点,但是口腔CT在临床检查中面临着很多问题和挑战,其中CT值的准确性和金属伪影尤为突出。因此,本文开展了CT值与金属伪影校正方法的研究,主要内容有：针对金属伪影,本文主要从三个方面进行校正：一是投影数据补偿,在图像重建前,对金属投影区域的数据采用插值的方法进行补偿,以此来达到去除金属伪影的目的。本文实现了线性插值与样条插值；二是迭代重建校正,将金属投影区域的数据舍弃掉,利用剩余数据进行迭代重建校正。对于该类方法本文实现了基于代数重建的ATR校正法以及基于统计迭代的MLEM方法；三是提出了一种基于投影数据加权的金属伪影校正法,此方法主要利用三部分的投影数据,分别是模板图像的投影数据、样条插值后的投影数据、修正后的投影数据,对这三部分投影数据采用加权的方式得到修正后的投影数据,最后重建获得校正后的图像。该方法既实现了每个投影角度下投影数据的连续性,也实现了角度与角度间投影数据的连续性,有效的去除了金属所引起的条状伪影。针对目前商用CT值校正方法的缺点,本文提出一种适用于口腔CT的CT值校正方法,该方法充分考虑到口腔CT重建图像中存在的噪声和伪影,在进行CT值校正前加入了图像预处理的步骤,有效降低了图像噪声以及伪影对CT值校正所带来的误差。将基于投影加权的校正方法应用于模拟金属伪影图像,图像信噪比提升22%；将改进的CT值校正方法应用实验室口腔CT,水模图像感兴趣区域CT值的准确性最高提升53%。
[Abstract]:At present, oral CT plays a more and more important role in the examination of dental diseases. By measuring the cumulative attenuation coefficient (or projection) of X-rays passing through human faults in all directions, the distribution of X-ray attenuation coefficients on the whole cross-section is obtained by computer reconstruction. Oral CT has the advantages of low dose and high spatial resolution, but it faces many problems and challenges in clinical examination. The accuracy of CT value and metal artifact are especially prominent. Therefore, this paper studies the correction method of CT value and metal artifact. The main contents are: for metal artifact, this paper mainly corrects from three aspects: first, projection data compensation, Before image reconstruction, interpolation method is used to compensate the data of the metal projection region to remove metal artifacts. In this paper, linear interpolation and spline interpolation are realized, and iterative reconstruction correction is used. The data of the metal projection region is discarded and the residual data is used for iterative reconstruction correction. For this kind of method, the ATR correction method based on algebraic reconstruction and the MLEM method based on statistical iteration are implemented in this paper. Third, a metal artifact correction method based on weighted projection data is proposed. This method mainly uses the projection data of three parts, namely, the projection data of template image, the projection data after spline interpolation, and the revised projection data. The modified projection data is obtained by weighted method, and the corrected image is reconstructed. This method not only realizes the continuity of the projection data at each projection angle, The continuity of projection data between angle and angle is realized, and the strip artifacts caused by metal are removed effectively. In view of the shortcomings of current commercial CT correction methods, this paper proposes a CT correction method suitable for oral CT. In this method, the noise and artifacts in the reconstruction image of oral CT are fully considered, and the steps of image preprocessing are added before the correction of CT value. The error caused by image noise and artifacts to CT value correction is reduced effectively. The projection weighted correction method is applied to simulate metal artifact image. The improved CT correction method is applied to the laboratory oral CT.The accuracy of CT value of the region of interest in the water model image is increased by 53%.
【学位授予单位】：东北大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：R816.98;TP391.41
，

本文编号：1636099