X-ray camera for computed microtomography of biological samples with micrometer resolution using Lu3Al5O12 and Y3Al5O12 scintillations

An x-ray camera for imaging with a spatial resolution in the micrometer and sub-micrometer range has been developed. The camera consists of a scintillator, light microscopy optics and a cooled charged-coupled device (CCD). A transparent scintillator converts the x-ray field into a visible light image which is projected onto the CCD by the light optics. A resolution of 0.8 mu m fwhm was achieved using 12-keV x rays and a 5-mu m thick commercially available Y3Al5O12:Ce (YAG:Ce) scintillator. The detective quantum efficiency (DQE)of the camera is mainly limited by the low absorption of x rays in the thin layer of the scintillator. To increase the absorption, Lu3Al5O12 (LAG) scintillators have been grown by liquid phase epitaxy (LPE). The characteristics of LAG activated with Eu or Tb have been investigated, in particular spectral emission, efficiency of x-ray to light conversion, and time response. Three-dimensional computed x-ray microtomography (3D-CMT) images of mouse bone samples:have been recorded with this camera using a 5-mu m thick YAG:Ce screen. The 3D-CMT system uses a parallel monochromatic x-ray beam extracted from the synchrotron radiation. A series of 2D x-ray projection images at different angles were recorded, and processed numerically to yield the 3D image of the bone structure with a voxel size of 1.8 mu m. Image features smaller than 3 mu m are clearly visible in the reconstructed tomogram. The quality of the images allows the analysis of the trabecular bone structure that is important for the understanding of the mechanisms of osteoporosis.