基于动态电流的锥束CT环状伪影校正方法

为了去除平板探测器中坏点和响应不一致探元引起的环状伪影对X射线计算机断层成像(CT)质量的影响，利用探元响应与管电流的线性相关关系，提出了一种基于探测器校正的环状伪影去除方法。检测出不同管电流下响应恒定的探元后，分别计算每个探元响应与管电流的相关系数，并检测出响应随机变化和迅速达到最大的探元，将检测出的探元记入坏点模板并进行校正。以单个管电流下所有探元响应的均值为基准，计算同一组管电流下各探元响应曲线方程与基准曲线方程的转化关系，得到探测器的一致性校正参数矩阵。依据坏点模板和一致性校正参数对各探元的输出响应进行校正。实验结果表明，该方法能够有效去除环状伪影，并改善图像信噪比。解决了现有坏点检测方法中阈值选择困难的问题，可适用于多种类型的探测器。

Abstract

In the flat panel detector, the ring artifacts caused by the defective and response non-uniformity pixels will affect the quality of X-ray computed tomography (CT). In order to solve the issue, the linear correlation between pixel response and tube current is applied, and a ring artifact removal method based on detector calibration is proposed. The pixels are detected, whose response is constant under different tube currents. Then the pixels with the response varying randomly or quickly reaching up to the maximum value are detected, and the correlation coefficients between each pixel channel response and the tube current are calculated. The pixels detected with the above mentioned methods are written into defective pixels map and corrected. With the reference of average response of all pixels under each tube current, the relationship between response and reference curve of the pixels under the same tube currents is calculated to obtain the identical correction matrixes of the detector. The output responses of the pixel are corrected according to the defective pixels map and the identical correction matrixes. Experimental results show that the proposed method can removes the ring artifacts effectively, and improves the signal to noise ratio of reconstruction image. In addition, it solves the problem of threshold selection with the existing defective pixal detection methods, which can be applied to different types of detectors.

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