Performance of a PET prototype demonstrator based on non-pixelated scintillators

Previous experimental results have demonstrated that a PET detector head based on a 20×10×10 mm LSO block read out by a Hamamatsu S8550 APD array is able to determine the impinging position of perpendicularly incident 511 keV photons with a resolution better than 2 mm FWHM. A prototype demonstrator using two of these detector heads was build to collect tomographic data. The axial and transaxial resolution measured in 2D OSEM and 2D FBP reconstructed images is better than 1.5 and 2 mm FVVHM respectively for radial distances less than 15 mm. A Monte Carlo simulation showed that a four-ring scanner based on these monolithic scintillator blocks has a 50% higher detection efficiency for single 511 keV photons in comparison to a similar system equipped with detector heads using a 4×8 matrix of 2×2×10 mm LSO pixels.