Measurement and deconvolution of glare in a microCT scanner for in vivo small animal imaging

Recently there has been a great deal of interest in X-ray microcomputed tomography (microCT) systems for in vivo small animal imaging. Although the spatial resolutions of these systems are good, the soft tissue contrast has been poor compared to human X-ray CT scanners. Many of these systems are based on phosphor screens coupled to charge coupled devices (CCD) using fiber optic tapers. The point spread function (PSF) for these systems is likely to include significant glare component. In this work we measured the glare component of the PSF of a microCT scanner developed in our laboratory. The measurements were based on the presampled edge spread function (ESF) obtained using an aluminum edge angled slightly with respect to the detector columns. The resulting ESF was fit with two Gaussian-shaped components. The wider component corresponds to the glare in the system and has a FWHM of 1.10 mm. We deconvolved this glare component from the projection data. The method was evaluated by applying the deconvolution method to projection data obtained from a mouse. The resulting projections were reconstructed using the 3D Feldkamp cone-beam reconstruction algorithm and compared to reconstructions obtained from the original projections without deconvolution. We conclude that glare deconvolution results in a modest improvement in the soft tissue contrast for small features.