A flat-field correction method for photon-counting-detector-based micro-CT

As low-dose computed tomography becomes a hot issue in the field of clinical x-ray imaging, photon counting detectors have drawn great attention as alternative x-ray image sensors. Even though photon-counting image sensors have several advantages over the integration-type sensors, such as low noise and high DQE, they are known to be more sensitive to the various experimental conditions like temperature and electric drift. Particularly, time-varying detector response during the CT scan is troublesome in photon-counting-detector-based CTs. To overcome the time-varying behavior of the image sensor during the CT scan, we developed a flat-field correction method together with an automated scanning mechanism. We acquired the flat-field images and projection data every view alternatively. When we took the flat-field image, we moved down the imaging sample away from the field-of-view with aid of computer controlled linear positioning stage. Then, we corrected the flat-field effects view-by-view with the flat-field image taken at given view. With a CdTe photon-counting image sensor (XRI-UNO, IMATEK), we took CT images of small bugs. The CT images reconstructed with the proposed flat-field correction method were much superior to the ones reconstructed with the conventional flat-field correction method.