Performance characteristics of a compact position-sensitive LSO detector module

Abstract

Abstract-We assembled a compact detector module comprised of an array of small, individual crystals of lutetium oxyorthosilicate:Ce (LSO) coupled directly to a miniature, metal-can, position-sensitive photomultiplier tube (PSPMT). We exposed this module to sources of 511-keV annihilation radiation and beams of 30-and 140-keV photons and measured spatial linearity; spatial variations in module gain, energy resolution, and event positioning; coincidence timing; the accuracy and sensitivity of identifying the crystal-of-first-interaction at 511 keV; and the effects of intercrystal scatter and LSO background radioactivity. The results suggest that this scintillator/phototube combination should be highly effective in the coincidence mode and can be used, with some limitations, to image relatively low-energy single photon emitters.Photons that are completely absorbed on their first interaction at 511 keV are positioned by the module at the center of a crystal. Intercrystal scatter events, even those that lead to total absorption of the incident photon, are placed by the module in a regular "connect-the-dot" pattern that joins crystal centers. As a result, the accuracy of event positioning can be made to exceed 90%, though at significantly reduced sensitivity, by retaining only events that occur within small regions-of-interest around each crystal center and rejecting events that occur outside these regions in the connect-the-dot pattern.Index Terms-Intercrystal scatter, lutetium oxyorthosilicate:Ce (LSO), position-sensitive photomultiplier tubes, small animal positron emission tomography (PET).

Performance evaluation of SiPM photodetectors for PET imaging in the presence of magnetic fields

“…17). The energy spectra for 18 F, for every crystal element, measured at 0 and 7 T are shown in Fig. 13.…”

“…13. Energy spectra obtained for each of the sixteen crystal elements, using 18 F when acquiring without (solid lines) and with (dashed lines) magnetic field. These spectra lack the high energy peak of 22 Na, and it has been acquired with a larger activity source than the other 22 Na spectra shown in this work, making the low energy background from intrinsic decay in the scintillator much less noticeable.…”

“…The flood field histogram shown in Fig. 12 was obtained during a 5 min acquisition with an 18 F source, accumulating a total of 5 Â 10 5 counts in singles mode. All the crystals of the matrix are clearly resolved.…”

Limitaciones tecnológicas de la tomografía por emisión de positrones (PET) para pequeños animales de laboratorio

“…Las principales características los detectores para imagen PET son que permita definir con la mayor precisión geométrica las posibles LORs, y que a su vez sea sensible y detecte un gran porcentaje de los fotones que alcancen dicho detector 28,29 . Para lo primero se precisan cristales pequeños y detectores sensibles a posición, con un fino muestreo espacial 30 .…”

“…3), lo que mejora la resolución intrínseca (resolución propia del detector; en la global del sistema intervienen más factores) respecto a la de los detectores de bloque 28,30,[34][35][36][37][38][39] . Estos diseños, sin embargo, tienen un coste más elevado, razón por la cual su uso se ha limitado a los sistemas de animales, con un número de detectores mucho menor que en los sistemas para humanos.…”