Evaluation of moderately cooled pure NaI as a scintillator for position-sensitive PET detectors
- Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Radiology
A new evaluation of pure NaI has been performed to determine if moderate cooling would lead to better performance than that of existing, activated NaI(Tl) position-sensitive detectors, particularly at high countrates. Using a freezer, an initial effort was performed to cool the crystal assembly to {minus}90 C (183 K). At this temperature, pure NaI has a decay constant of 35 nsec, a light output which is about 20% that of room temperature NaI(Tl), and an energy resolution of 15%. For the PET applications the signal of room temperature (25 C) NaI(Tl) is normally pulse clipped, reducing the light output to 40% of the unclipped signal and yielding an energy resolution of 10.5%. Since the long decay of NaI(Tl) causes it to suffer more significantly than pure NaI from pre-pulse pileup, the difference in energy resolution between the two crystals at high countrates will be reduced. Also, a significantly shorter trigger deadtime with pure NaI will lead to a reduction in coincidence deadtime losses in PET. Computer simulations of large-area crystals operating at high countrates have been performed to quantify their trigger deadtime behavior and position resolution as a function of light output and pulse decay time. Having gained experience with the practical issues of cooling large crystals, measurements of position resolution have been performed with a NaI bar detector of similar geometry to the NaI(Tl) detectors in use in the PENN-PET scanner.
- DOE Contract Number:
- FG02-88ER60642
- OSTI ID:
- 276524
- Report Number(s):
- CONF-951073-; ISSN 0018-9499; TRN: 96:018029
- Journal Information:
- IEEE Transactions on Nuclear Science, Vol. 43, Issue 3Pt2; Conference: IEEE nuclear science symposium and medical imaging conference, San Francisco, CA (United States), 21-28 Oct 1995; Other Information: PBD: Jun 1996
- Country of Publication:
- United States
- Language:
- English
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