Design and development of a high performance micro-CT system for small-animal imaging

Abstract

The goal of this work was the development of a lowcost micro-CT scanner, which could be used as an add-on in our previously developed PET systems for small-animals. The scanner design consists of a single-processor computer controlling a micro-focus X-ray tube and a flat panel detector, assembled in a common rotating gantry. The geometrical configuration was selected to achieve a spatial resolution of about 12 lp/mm with a field of view appropriate for small animals such as mice and rats. The radiated dose is controlled during the acquisition by two different elements: an aluminium filter and a tungsten shutter, attached to the X-ray source. The shutter is controlled by the computer in synchronism with the gantry rotation and the detector image integration. In order to achieve high performance with regards to per-animal screening time and cost, the acquisition protocol is able to take advantage from the highest frame rate of the detector also performing onthe-fly corrections for the detector raw data. These corrections include geometrical misalignments, sensor non-uniformities and defective elements, as well as conversion to attenuation images. An FDK reconstruction algorithm adapted to the specific conebeam geometry has been implemented. Symmetries are exploited to accelerate the algorithm and fast back-projection techniques have been developed for those protocols where high resolution is not a requirement.