Answer to Question #1567 Submitted to "Ask the Experts"

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, 2^nd 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 Website. 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
MS Professor (Medical Physics)
University of Alabama at Birmingham