Performance study of a 3D small animal PET scanner based on BaF2 crystals and a photo sensitive wire chamber

A 3D small animal PET scanner, designed and built at the University of Brussel, has been operational since the beginning of 1996. The scanner has a transaxial field of view (FOV) of 110 mm and an axial FOV of 52 mm. The absolute sensitivity is around 35,000 coincidences s(-1) MBq(-1) for a point source at the center of the scanner and the time resolution is 29 ns FWHM. To measure the achievable spatial resolution, a thin Na-22 source was scanned at various distances from the scanner axis. The resolution in a reconstructed image for a source close to the center is 3.0 mm FWHM. This figure can be improved at the expense of the sensitivity by lowering the voltage on the anodes in the wire chamber. Finally, to assess the overall image quality, scans were made of a cylindrical phantom with holes of varying diameter.