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J Nucl Med. 2008; 49 (Supplement 1):435P
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Technologist Student Abstracts

Technologist Student Papers IV

Evaluating an inexpensive wipe counter for PET facility

John Sieja1, Michael Zimmer1, Peter Cutrera1, Nancy McDonald1 and Sterwart Spies1

1 Northwestern Memorial Hospital, Chicago, Illinois

2239

Objectives: Radiation safety requires that wipe testing be performed to determine removable contamination. The purpose of this study was to evaluate a portable GM wipe test counter (Inspector, S. E. International, Inc.) in a PET facility utilizing F-18 (FDG).

Methods: Two F-18 FDG standards were prepared and activity measured in an AtomLab 100 dose calibrator (Biodex Medical Systems). Standards were decayed approximately 21 hours and then placed in the wipe counter test plate and counted three times for one minute with 120 degree rotation. Mean counts per minute (cpm) were calculated by subtracting background counts yielding net cpm. Activity of both standards was calculated at the precise counting time using appropriate decay factors. Percent efficiency and lower limit of detection for F-18 FDG was calculated. In order to verify daily instrument performance, a 1µCi Cs-137 button source (Spectrum Techniques) was counted three times and the mean net cpm and lower and upper counting limits calculated (±10%).

Results: Initial activity of each standard was 59.0µCi and 54.6µCi. After decay (21 h), the activity of each standard was 0.0245µCi and 0.0220µCi and counts were 6502 cpm and 5408 cpm, respectively. The calculated mean counting efficiency for F-18 FDG was 11.5% with a lower limit of detection of 262 dpm. The mean counts for the Cs-137 source was 2610 net cpm with a lower and upper range of 2349 to 2871 net cpm.

Conclusions: The F-18 counting efficiency of a portable GM wipe counter was 11.5% with a lower limit of detection of 262 dpm. As a result, the portable wipe counter evaluated can be used in a PET facility to evaluate removable contamination levels.





This Article
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Google Scholar
Right arrow Articles by Sieja, J.
Right arrow Articles by Spies, S.
PubMed
Right arrow Articles by Sieja, J.
Right arrow Articles by Spies, S.