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Radiological Protection of Patients |
For a description of radiation quantities and units used on this page, please click here.
Optimizing radionuclide therapy procedures is somewhat different than in diagnostic nuclear medicine. In diagnostics, you want to reach a balance between the administered activity and the image quality necessary for a correct diagnosis. In therapy, optimization has the objective of getting the prescribed dose to the tissue or organ under treatment in order to reach a desirable biological effect. Therefore, optimization means individual dose planning based on uptake measurements, the volume of the treated organ, dose calculations and a correct measurement of the activity to administer. Practically, individual dose planning has, so far, only been used in treatment of thyroid diseases but much work is being done to expand this to any kind of radionuclide therapy.
As a rule, a pregnant woman should not be treated with a radioactive substance unless the radionuclide therapy is required to save her life: in that extremely rare event, the potential absorbed dose and risk to the fetus should be estimated and conveyed to the patient and to you as a the referring physician. Considerations may include terminating the pregnancy. For further information, see first topic in 'Therapeutic Nuclear Medicine - Patients'.
The ICRP (ICRP Publication 94: Release of Nuclear Medicine Patients after Therapy with Unsealed Sources) recommends that the decision should be determined on an individual basis, taking into account patients' pattern of contact with other people, their age and that of persons in the home environment, patients’ wishes, and local social and infrastructure issues. The cost of hospitalization, and radiation exposure of hospital staff should also be considered.
The BSS (paragraph II-9) states that "..the dose of any comforter or visitor of patients shall be constrained so that it is unlikely that his or her dose will exceed 5 mSv during the period of the patient's diagnostic examination or treatment. The dose to children visiting patients who have ingested radioactive material should be similarly constrained to less than 1 mSv."
A profile of the time spent at certain distances from the patient can be developed for the spouse, and for other family members, which can then be used to estimate cumulative dose. If patients and caregivers then follow simple radiation protection precautions, doses would rarely approach the dose constraints. See section on the decision to discharge the patient.
The decision should be taken together with a medical physicist or radiation protection officer.
There is no standardization among countries for discharge or release criteria. Some use a fixed radioactivity level, some use a dose rate from the patient, and others use an estimated dose to family members following return home. See section on the decision to discharge the patient. Most other guidelines are specific for iodine-131 only.