CT imaging of small animals using monochromatized synchrotron X-rays

Rats and chicken embryos were imaged in vivo with a prototype multiple energy computed tomography (MECT) system using monochromatized X-rays from the X17 superconducting wiggler at the National Synchrotron Light Source (NSLS). The CT configuration consisted of a horizontal, low-divergence, fan-shaped beam, 70-mm wide and 0.5-mm high, and a subject rotating about a vertical axis. A linear-array high-purity Ge detector with 140 elements, each 0.5-mm wide and 6-mm thick, was used with a data acquisition system that provides a linear response over almost six orders of magnitude of detector current. The dual photon absorptiometry (DPA) algorithm was applied to images of the rat head acquired at 20 and 45 keV to obtain two new images, one representing the low-Z and the other the intermediate-Z element group. The results indicate that the contrast resolution and the quantification accuracy of the images improve stepwise; first, with the monochromatic beam and, second, with the DPA method. The system is a prototype for a clinical brain scanner