The scaffold-based tissue engineering of bones is an extremely promising concept with regard to the regeneration of major bone defects due to trauma, tumour or developmental abnormalities as well as for the treatment of pseudo-arthroses. The in vivo testing of implants is a significant phase in the development of specimens for the clinical application of suitable scaffolds. Within our Project a new Scaffold made of Poly-lactid-co-glyocolid-acid and CaP was developed. Half of the Scaffolds were populated with allogen rabbit mesenchymal stem cells in the fixed bed bioreactor (3D-cultivation). The two Scaffold-Groups, populated and unpopulated, were testet in the Critical Size Defect of the Chinchilla Bastard rabbit in vivo. The collection of an optimal amount of information from these initial – clinical - tests demands, ideally, the most diagnostically conclusive studies possible. We tested the procedure of flat panel volumetric computer tomography (fpvCT) thus far virtually untried in the area of bone tissue engineering for the in vivo evaluation of small animal experiments and compared it with other methods (projection radiography, micro-CT, histology). The main questions were whether in situ osteosynthesis decreased representability (artefact formation), the scaffold could be demonstrated by means of fpvCT, and whether the course of degradation and bone growth could be observed, the course of growth precisely evaluated, neoformation of vessels demonstrated in the osteotomic cleft, and what conclusions could be reached with regard to animal models and osteosynthesis. We worked with a CT from the company GE Global Research, Niskayuna, New York. This flat panel volumetric computed tomograph functions with two flat panel radiographic sensors with a resolution of 1024x1024 pixels in each instance. We were able to demonstrate that the fpvCT is an alternative to be considered seriously in terms of the in vivo evaluation of small animal experiments on behalf of scaffold-based tissue engineering. It is superior to projection radiography and can replace the micro-CT, if high resolution is not required. Major advantages of this method over the micro-CT are the shorter scan time, the lower radiation exposure, the larger presentable area and the possibility of carrying out several experiments on a single animal over the course of time. In terms of resolution the fpvCT is superior to the micro-CT. Above all with respect to issues concerning the neoformation of bone and the differentiation between degraded scaffold and new bone, histology is indispensable.