Volumetric monochromatic x-ray tomography of the lungs

Monochromatic x-rays were produced by inverse Compton scattering resolution from counter-propagation of a tunable free electron laser electron beam and its own infrared photon beam. In a manner analogous to electron beam CT, a mechanism was developed here for obtaining multiple projection views with monochromatic x-rays by deflecting x- rays off of mosaic crystals mounted on rotating stages. These crystals are both energy and angle selective. X-rays are detected digitally when they strike a phosphorescent screen mounted in front of a CCD camera. Using this system, multiple projection images of a 3D phantom and of rat lungs ex vivo were obtained. In an alternate micro-CT arrangement, rat lungs in situ were imaged by rotating the rat in front of both a polychromatic beam from a molybdenum target x-ray tube and the same beam monochromatized with a mosaic crystal. In the first arrangement, depth information was revealed by relative position changes of features seen in each projection and the approximately 0.16 mm thick walls of a catheter were visible in the images. Using conventional tomography, the projections were reconstructed into slice images. Overall, these monochromatic x-ray imaging methods offer reduced x-ray dose, the potential for improved contrast resolution, and now 3D information.