<title>Image quality characteristics of a novel x-ray detector with multiple screen: CCD sensors for real-time diagnostic imaging</title>

We have presented the principle of an x-ray detector based upon a screen coupled to an array of multiple CCD sensors. We now focus on the characterization of the image quality: resolution (MTF) and noise behavior in the overlap area. Simple low F lenses likely show distortion which means that not all imaged pixels have the same magnification. This may affect resolution. In the overlap area the image is reconstructed by interpolation between two sensors. Interpolation affects the noise properties so care must be taken in order to avoid that the noise characterization of the reconstructed image mosaic becomes spatially non uniform.We present an analysis of the influence of lens distortion and interpolation in the overlap area on the image mosaic. The image processing appears not to diminish the image quality provided the processing parameters are set correctly. We therefore present a robust extraction algorithm. In order to evaluate in real-time the image quality of the proposed detector system, we are building a 2 by 2 lens-CCD sensor system as a lab prototype. The main interest is on MTF and quantum noise properties. The hardware is designed such that also the lens distortion can be compensated. This enables relative cheap optical components with low F and a short building length. We have obtained and will present radiographic exposures of static phantoms.