A ceramic version of the LSO scintillator

Although LSO is one of the most successful scintillator developments for medical diagnostics in the last two decades, good single crystals are not commercially available in any quantity. Consequently, we explored the feasibility of developing a ceramic version of the material, which requires a considerably lower temperature to consolidate the material to essentially crystalline density. Consolidation of the ceramic was achieved by hot pressing at temperatures up to 1700C and pressure of 8000 psi. Hot pressing causes a loss of oxygen resulting in strong coloration of the ceramic, which had. to be removed by heating ("bleaching") in air at approximately 1100C. The resultant specimens were colorless and highly translucent, but the anisotropic nature of the crystal structure precluded the achievement of full transparency. The scintillation performance of the resulting ceramics was characterized and compared with that of high light-output LSO single crystals. The scintillation efficiency as measured by energy spectra generally fell in the range of 50-60% of that of the crystals. While this would be adequate for PET applications, the limited transparency provides a barrier to such use. An alternative application would be in signal integrating techniques, such as CT, where it could provide an alternative to GOS but with higher speed. Here, the problem of afterglow assumes major importance. The afterglow is a function of many factors, including conditions of excitation. Further work on improving the LSO ceramics is considered.