X射线转换屏辐照损伤校正方法研究

Study on the Correction Method of Radiation Damage of X-ray Conversion Screen

  • 摘要: 高分辨X光照相利用MeV级X光的强穿透性及微焦点X光机的高分辨能力对样品进行透射照相及图像分析,能够获得待检测样品的高精度几何参数。在对样品进行高分辨X光成像过程中,长时间、高剂量的辐照会对X光转换屏造成损伤,造成转换效率的不断降低。对高分辨X光照相中转换屏的辐照损伤问题进行了研究。利用样品DR图像集内不含样品区域的灰度数据开展了图像灰度随照射剂量、照射时间的变化规律分析,建立了DR图像的灰度变化规律,将灰度变化规律分解为由转换屏受辐照损伤造成的线性下降以及由X光光源剂量率波动导致的随机波动两个分量,其中线性分量的斜率为转换屏的辐照损伤系数。建立了转换屏辐照损伤校正方法,经过校正后的DR图像在灰度上与真值图像的平均相对误差小于0.6%,比校正前小了近一个数量级。建立的转换屏辐照损伤校正方法能够有效地校正由于转换屏辐照损伤以及光源剂量波动带来的DR图像灰度非预期变化,为后续的图像定量分析的精确化、自动化奠定基础。

     

    Abstract:
    Background  High-resolution X-ray photography utilizes the strong penetration capability of MeV-level X-rays and the high-resolution capacity of microfocus X-ray machines to conduct high-resolution transmission photography and image analysis on devices, thereby obtaining precise profile parameters of the device under inspection. During the process of high-resolution X-ray imaging of the device, long timed exposure and high doses of radiation can damage the X-ray conversion screen, leading to a continuous decrease in its conversion efficiency.
    Purpose This study focuses on the radiation damage issue of the X-ray conversion screen in high-resolution X-ray photography. The goal is to establish a correction method for irradiation damage image.
    Methods Starting with the grayscale data from areas within a certain workpiece’s DR (Digital Radiography) image set that do not contain the device, the research analyzes the changes in image grayscale as a function of radiation dose and exposure time, establishing a model for the change pattern of DR image grayscale. The change in image grayscale due to radiation dose is decomposed into two components: a linear decline caused by damage to the conversion screen and random fluctuations caused by variations in the X-ray source dose rate. By fitting a linear curve to the distribution pattern curve, these two components are separated, where the slope of the linear component represents the radiation damage coefficient of the conversion screen. Research has also been conducted on methods to correct for radiation damage to the conversion screen.
    Results After correction, the average relative error between the grayscale of the corrected DR images and the true value images is less than 0.6%, which is nearly an order of magnitude smaller than before correction.
    Conclusions The established method for correcting radiation damage to the conversion screen effectively corrects for unexpected changes in DR image grayscale due to damage to the conversion screen and fluctuations in the light source dose, laying the foundation for more precise and automated quantitative image analysis in subsequent steps.

     

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