Activity thresholds for patient instruction and release for positron emission tomography radionuclides

The use of unconventional or novel radionuclides for positron emission tomography (PET) is becoming more prevalent in both nuclear medicine diagnosis and therapy. Many of these radionuclides are produced in cyclotrons or are further eluted from generators. Although half-lives from many of these unconventional PET radionuclides are considered relatively short (minutes to hours, but some are days) and the intent of their use is often as a diagnostic imaging agent, patient release criteria and patient radiation safety instruction regulatory requirements are based on estimated dose to a member of the public. This paper reviews a method referenced routinely for patient release criteria as found in U.S. Nuclear Regulatory Commission guidance, estimates fundamental quantities used in the method, compares estimated quantities with the published literature, and calculates release and patient radiation safety instruction criteria for several novel PET radionuclides used in nuclear medicine. It should be recognized that some quantities of novel PET radionuclides in use today reach the threshold for patient safety instruction using conservative model procedures for patient release.