Soft-tissue contrast resolution within the head of human cadaver by means of flat-detector-based cone-beam CT

In this paper, soft tissue contrast visibility in neural applications is investigated for volume imaging based on flat X-ray detector cone-beam CT. Experiments have been performed on a high precision bench-top system with rotating object table and fixed X-ray tube-detector arrangement. Several scans of a post mortem human head specimen have been performed under various conditions. Hereby two different flat X-ray detectors with 366 × 298mm² (Trixell Pixium 4700) and 176 × 176mm² (Trixell Pixium 4800) active area have been employed. During a single rotation up to 720 projections have been acquired. For reconstruction of the 3D images a Feldkamp algorithm has been employed. Reconstructed images of the head of human cadaver demonstrate that added soft tissue contrast down to 10 HU is detectable for X-ray dose comparable to CT. However, the limited size of the smaller detector led to truncation artifacts, which were partly compensated by extrapolation of the projections outside the field of view. To reduce cupping artifacts resulting from scattered radiation and to improve visibility of low contrast details, a novel homogenization procedure based on segmentation and polynomial fitting has been developed and applied on the reconstructed voxel data. Even for narrow HU-Windows, limitations due to scatter induced cupping artifacts are no longer noticeable after applying the homogenization procedure.