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Answer to Question #1567 Submitted to "Ask the Experts"Category: Nuclear Medicine Patient Issues — PET The following question was answered by an expert in the appropriate field: Q
What is the gamma factor for the 18F used in PET (positron emission tomography) scans? Where can I find the information on shielding requirements for a PET scanner?
A
The exposure rate constant for 18F is: Γ = 5.70 (R cm2/mCi hr) at 1 cm. (Reference: Saha, Physics and Radiobiology of Nuclear Medicine, 2nd Ed., 2001). In regard to the question regarding shielding requirements for PET, according to my regulatory and institutional sources, there are none specifically for PET. However, as with any radiation source, one must take appropriate steps to comply with regulatory exposure limits for unrestricted areas and to implement ALARA (as low as reasonably achievable) throughout the facility. With 18F having an HVL of 0.4 cm in lead, one might consider more novel approaches to exposure reduction, such as appropriately shielded source containers, remote handling and injection devices, and separate waiting areas for dosed patients. The magnitude of the exposure problem will depend greatly on the activity of the dose and patient load. You might also like to review the references listed in the answer to Question #387 on this Web site. If specific questions arise, perhaps the best advice would be to contact an existing PET facility and ask to speak with its radiation safety officer. Michael A. Thompson
Answer posted on January 24, 2002. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.
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