A calibrating method of flat panel detector based on cone beam computed tomography

To eliminate reconstructive slice artifacts of cone beam CT caused by defects in flat panel detector, a calibration method is proposed for projected images. On the basis of dark image and gain non-uniformity calibration, the gain coefficient is derived and bad pixels are identified based on a histogram analysis of gain coefficient, mathematical expectation together with variance of output. Then an appropriate interpolation method is designed according to the distribution of bad pixels. For calibrating the unstable dark images, the data under a local lead shield is accumulated, and the fluctuations on each line is computed and corrected line by line. Experimental results show that our proposed method can homogenize the gray level of projected images and reduce output fluctuations and reconstructive artifacts effectively.