Are restrictions to behaviour of patients required following fluorine-18 fluorodeoxyglucose positron emission tomographic studies?

The clinical use of positron emission tomography (PET) is expanding rapidly in most European countries. It is likely therefore that patients receiving the tracer fluorine-18 fluorodeoxyglucose ((18)FDG) will be discharged to come into contact with family members, members of the public and ward staff . There are few direct measurements on which to base any recommendations wi th regard to radiation protection, and so we have measured the dose rates f rom patients undergoing clinical PET examinations in our centre. Seventy-fi ve patients who underwent whole-body and brain (18)FDG PET examinations wer e studied. Dose rates were measured at 0.1, 0.5, 1.0 and 2.0 m from the mid thorax on leaving the department. The median administered activity was 323 MBq with a 95th percentile value of 360 MBq. The median dose rates measure d at the four distances were 90.0, 35.0, 14.0 and 5.0 mu Sv h(-1) (the medi an dose rates per unit administered activity at 2 h post injection were 0.3 1, 0.11, 0.04 and 0.02 mu Sv h(-1) MBq(-1)). The corresponding 95th percent ile values were 174.0, 69.0, 29.0 and 7.5 mu Sv h(-1) (0.43, 0.2, 0.08 and 0.03 mu Sv h(-1) MBq(-1)). A number of social situations were modelled and an annual dose limit of 1 mSv was used to determine whether restrictive beh avioural advice was required. In the case of nursing staff on wards a value of 6 mSv was regarded as the annual limit, which translates to a daily lim it of approximately 24 mu Sv. There is no need for restrictive advice for p atients travelling by public or private transport when they leave the depar tment 2 h after the administration of (18)FDG. Similarly, there is no need for restrictive advice with regard to their contact with partners, work col leagues or children of any age, although it should be stressed that childre n should not accompany the patient to the scanning department. The only pos sible area of concern is in an oncology ward, where patients may be regular ly referred for PET investigations and other high activity radionuclide stu dies and are partially helpless. Even in this area, however, it is unlikely that a nurse would receive a daily dose of more than 24 mu Sv. We conclude that there is no need for restrictive advice for patients undergoing (18)F DG PET studies given the current administered activities.