An XXL-CT-scan of an XXL Tyrannosaurus rex skull

摘要

In 2016, the Dutch national natural history museum, Naturalis Biodiversity Center in Leiden, will present its Tyrannosaurus rex skeleton to the public, the first original T. rex skeleton on permanent display outside North America. The 66-million year old fossil was discovered in 2013 near Jordan, Montana, USA, and excavated by PL and AS and team in the autumn of the same year. The well-preserved and nearly complete skull made a CT scan of the fossil, prior to preparation, mandatory. The skull measures almost 1.5 m in length, and the surrounding sandstone matrix, in turn wrapped in a protective plaster jacket, made the use of a conventional CT system not an option - both because of specimen weight, as well as specimen size and thus required penetration length. Therefore, the T. rex skull was scanned with the unique XXL-CT system of the Fraunhofer Development Center X-ray technology (EZRT), which is capable of handling specimens of up to 10 metric tons in weight and a few meters in diameter (e.g. complete cars). The X-ray source for this system is a pulsed 9 MeV linear accelerator. This allows for enough penetration power in both very large and highly absorbing specimens. The X-ray detector is a custom-made line detector array, 4 m wide. In this contribution we describe the XXL-CT system and present the challenges, considerations and preliminary results of the CT-scan of the 1.5 m long T. rex skull.