Evaluation of moderately cooled pure NaI as a scintillator for position-sensitive PET detectors

Journal Article · Sat Jun 01 04:00:00 EDT 1996 · IEEE Transactions on Nuclear Science

DOI:https://doi.org/10.1109/23.507251· OSTI ID:276524

Wear, J A; Karp, J S; Haigh, A T; Freifelder, R ^[1]

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1. 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--
• Journal Information: IEEE Transactions on Nuclear Science, Journal Name: IEEE Transactions on Nuclear Science Journal Issue: 3Pt2 Vol. 43; ISSN 0018-9499; ISSN IETNAE
• Country of Publication: United States
• Language: English

Related Subjects

44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
55 BIOLOGY AND MEDICINE
BASIC STUDIES
AMBIENT TEMPERATURE
COMPUTERIZED SIMULATION
EVALUATION
NAI DETECTORS
POSITION SENSITIVE DETECTORS
POSITRON COMPUTED TOMOGRAPHY
RADIOISOTOPE SCANNERS