SIMULATION OF LIGHT OUTPUT FROM NARROW SODIUM-IODIDE DETECTORS

The use of narrow scintillators in imaging devices raises the question of whether there is enough light output that can yield reasonable ene rgy and spatial resolutions. Compared to scintillation within large-ar ea detectors (such as those used in conventional gamma cameras), scint illation photons within narrow detectors are expected to undergo more reflections because of the proximity of the detector surfaces. In this study, we use simulation methods to estimate the light output from lo ng, narrow sodium iodide crystals, and to investigate the effects of d etector geometry and detector surface reflection properties on the fra ction of scintillation photons that are able to leave the crystal thro ugh the exit window (on one of the long, narrow sides). Our simulation s show that the light output from a 3.5-mm wide by 10-mm high by 300-m m long detector can result in reasonable energy resolutions. Our simul ations also suggest that, in conjunction with the use of external refl ectors, a crystal that has its sides polished to a smooth finish resul ts in better light output than one with sides grounded to a rough fini sh.