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After some treatments with radioactive medicines or seeds, you give off a little radiation for a while. Before you go home, the team checks that the people around you will receive only a small, safe dose, taking your home and family into account, and gives you written instructions. If that is not yet possible you stay in a single room until it is.
Release is governed by dose to other people. Members of the public are subject to the public dose limit (1 mSv a year); family and friends who knowingly help are carers and comforters, whose exposure is controlled by a dose constraint, commonly 5 mSv per episode for an adult and 1 mSv for children and for the embryo or fetus of a pregnant carer, with more lenient values possible for elderly people (IAEA SSG-46 para 2.49). Before release, the medical physicist or radiation protection officer establishes that retained activity is low enough to stay within those limits and constraints, for example by integrating the measured dose rate over the activity, energy and effective half-life, taking into account the patient's living conditions, children and pregnant women at home, excreta and incontinence; the assumptions must match the written instructions given (SSG-46 4.247, 5.258). Carers must have received and understood information on radiation risks before they provide care (GSR Part 3 para 3.153, quoted in SSG-46). Written instructions go to the patient or guardian (SSG-46 4.248; UK IR(ME)R 2017 reg 12(6) and (7), before leaving).
The US rule allows release when no other individual is likely to receive more than 5 mSv, requires written instructions when anyone could receive more than 1 mSv, and requires breastfeeding guidance when a nursing infant could exceed 1 mSv (10 CFR 35.75); the basis for release must be recorded when it uses retained activity, an occupancy factor below 0.25 at 1 m, an effective half-life or tissue shielding, and kept for 3 years (35.2075). A patient who cannot be released is kept in a private room with a private toilet, the door posted, visitor time noted and items leaving the room surveyed or treated as radioactive waste (35.315), by staff given annual radiation safety instruction (35.310). Many countries also use a retained-activity limit for iodine-131 (most EU member states 400 to 600 MBq; Germany 250 MBq; Japan 500 MBq or under 30 microsieverts an hour at 1 m) (IAEA SRS-63). The IAEA and ICRP advise that the decision is individual and that dose limits and constraints, not secondary limits such as retained activity, should drive it; SSG-46 notes that systematic dose monitoring of family members is not necessary. Permanent implants follow the same framework (SSG-46 5.257 to 5.261), with a wallet card and advice about seed expulsion, later surgery and death.
Why: These limits keep the dose to the people around the patient small, while letting family help and comfort them.
“For an adult carer or comforter, a value of dose constraint commonly used is 5 mSv effective dose per episode.”
International Atomic Energy Agency, jointly sponsored by PAHO and WHO 2018
Why: Fixed retained-activity limits rest on worst-case models and can keep people in hospital who could safely go home.
“The control arrangements should focus on the dose limits or dose constraints that are generally applied, rather than on secondary limits, such as retained activity.”
Why: A qualified person checks the numbers for each patient before they leave.
“The medical physicist or RPO at the nuclear medicine facility should establish prior to the release of a patient that the retained radioactivity in the patient is such that the doses that could be received by members of the public would not exceed public dose limits, and would be unlikely to exceed the relevant dose constraints for both members of the public and carers and comforters.”
International Atomic Energy Agency, jointly sponsored by PAHO and WHO 2018
Why: A measurement on the patient, decayed forward, gives a realistic estimate rather than a worst case.
“An acceptable method of estimating the acceptable retained activity for patients being discharged from hospitals is to calculate the time integral of the ambient dose equivalent rate, considering the activity, energy and effective half-life of the radionuclides.”
International Atomic Energy Agency, jointly sponsored by PAHO and WHO 2018
Why: The same treatment is safe to go home with in one household and not yet in another.
“Special consideration should be given to incontinent patients.”
International Atomic Energy Agency, jointly sponsored by PAHO and WHO 2018
Why: A carer's exposure is accepted because they choose to help knowing what it involves.
“Registrants and licensees shall ensure that no individual incurs a medical exposure as a carer or comforter unless he or she has received, and has indicated an understanding of, relevant information on radiation protection and information on the radiation risks prior to providing care and comfort to an individual undergoing a radiological procedure.”
International Atomic Energy Agency, jointly sponsored by PAHO and WHO 2018
Why: The calculation only holds if the patient knows and follows the precautions it assumed.
“In the case of patients undergoing treatment or diagnosis with radioactive substances, the employer’s procedures must provide that, where appropriate, written instructions and information are provided to—”
Why: Some radioactive medicines pass into breast milk.
“If the total effective dose equivalent to a nursing infant or child could exceed 1 mSv (0.1 rem) assuming there were no interruption of breast-feeding, the instructions must also include—”
US Nuclear Regulatory Commission (Code of Federal Regulations, via eCFR) 2007
Why: A record shows how the decision was made if it is questioned later.
“The records required by paragraphs (a) and (b) of this section must be retained for 3 years after the date of release of the individual.”
US Nuclear Regulatory Commission (Code of Federal Regulations, via eCFR) 2005
Why: This protects other patients, visitors and staff until the activity falls.
“A private room with a private sanitary facility; or”
US Nuclear Regulatory Commission (Code of Federal Regulations, via eCFR) 2003
Why: Nurses need to know how to care for the patient safely, and an emergency or death needs specific precautions.
“A licensee shall provide radiation safety instruction, initially and at least annually, to personnel caring for patients or human research subjects who cannot be released under § 35.75.”
US Nuclear Regulatory Commission (Code of Federal Regulations, via eCFR) 2003
Why: Staff elsewhere, or funeral directors, need to know what was given and whom to call.
“To facilitate this, the patient should be given a small card with details of their treatment and contact details for a radiation protection specialist/medical physicist associated with the department responsible for the therapy”
How care is usually carried out, read from the guidelines and standards cited. Your own team's protocol and their judgement come first; this page is for understanding it, not for doing it yourself.
An individual decision based on the dose others could receive, using dose limits for the public and dose constraints for carers (commonly 5 mSv per episode for adults and 1 mSv for children and for the fetus of a pregnant carer), estimated by a physicist from measured dose rates and the patient's home circumstances, with written instructions consistent with that estimate, given before the patient leaves (IAEA SSG-46 2018; IAEA SRS-63 2009; ICRP 94; 10 CFR 35.75; IR(ME)R 2017 reg 12). The IAEA and ICRP favour the dose approach over retained-activity limits and say that where they conflict the dose approach is the more fundamental; many European countries still apply retained-activity limits in law, and a patient there is bound by them. None of these sources grades its recommendations.
International Atomic Energy Agency, jointly sponsored by PAHO and WHO 2018 · International Atomic Energy Agency 2009 · International Commission on Radiological Protection (Annals of the ICRP 34(2)) 2004 · US Nuclear Regulatory Commission (Code of Federal Regulations, via eCFR) 2007 · UK legislation (legislation.gov.uk) 2017
Where it differs: A patient stays until the activity left in the body is below a set value. For iodine-131: most EU member states 400 to 600 MBq (range about 95 to 800), Germany 250 MBq (3.5 microsieverts an hour at 1 m) in table 10 but 75 MBq in table 9 of the same report, Japan 500 MBq or under 30 microsieverts an hour at 1 m, Sweden 600, Finland 800, Australia 600, the former IAEA guidance level 1,100 MBq (SRS-63 tables 9 and 10). EU recommendations then set how long instructions apply by dose rate at release, from 24 hours under 3 microsieverts an hour at 1 m to 3 weeks under 40 (table 11).
Evidence: SRS-63 reports that some retained-activity models are unduly conservative, overstate doses and lead to unnecessary hospital stays.
Where it differs: Release is allowed when no other person is likely to exceed 5 mSv, with written instructions above 1 mSv; NUREG-1556 Volume 9 gives default activity tables and methods for patient-specific calculation. This allows considerably higher activities to be released than retained-activity limits do.
Evidence: SRS-63 reports that competent and cooperative US patients are routinely discharged with up to 8 or 9 GBq of iodine-131, and that this has produced some previously unreported practices that need to be kept under review. NUREG-1556 itself could not be read.
US Nuclear Regulatory Commission (Code of Federal Regulations, via eCFR) 2007 · International Atomic Energy Agency 2009
Where it differs: A 2025 modelling study comparing release approaches for lutetium-177 PSMA and dotatate, iodine-131, iodine-131 MIBG and samarium-153 recommends a dose constraint of 1 mSv per administration for people in contact with the patient, and keeping patients in the department for at least 4 to 6 hours, because exposure of other passengers on public transport should be considered.
Evidence: A single modelling study; abstract read only.
| Recommendation | Grade, as printed | Source |
|---|---|---|
| Release where no other individual is likely to exceed 5 mSv “A licensee may authorize the release from its control of any individual who has been administered unsealed byproduct material or implants containing byproduct material if the total effective dose equivalent to any other individual from exposure to the released individual is not likely to exceed 5 mSv (0.5 rem).” | Regulatory requirement (ungraded) | US Nuclear Regulatory Commission (Code of Federal Regulations, via eCFR) 2007 |
| Written instructions when another individual could exceed 1 mSv “A licensee shall provide the released individual, or the individual's parent or guardian, with instructions, including written instructions, on actions recommended to maintain doses to other individuals as low as is reasonably achievable if the total effective dose equivalent to any other individual is likely to exceed 1 mSv (0.1 rem).” | Regulatory requirement (ungraded) | US Nuclear Regulatory Commission (Code of Federal Regulations, via eCFR) 2007 |
| Children as carers, and the fetus of a pregnant carer, constrained to 1 mSv per episode “The same approach of constraining the effective dose to the embryo or fetus to 1 mSv per episode is often taken.” | Safety Guide recommendation (ungraded) | International Atomic Energy Agency, jointly sponsored by PAHO and WHO 2018 |
| Decide hospital stay or release on an individual basis “The decision to hospitalise or release a patient should be determined on an individual basis.” | Consensus (ungraded) | International Commission on Radiological Protection (Annals of the ICRP 34(2)) 2004 |
| Young children, infants and visitors not giving care treated as members of the public “The present report recommends that young children and infants, as well as visitors not engaged in direct care or comforting, should be treated as members of the public (i.e. be subject to the public dose limit).” | Consensus (ungraded) | International Commission on Radiological Protection (Annals of the ICRP 34(2)) 2004 |
| Systematic dose monitoring of others is not necessary “Published data suggest that systematic dose monitoring is not necessary” | Safety Guide recommendation (ungraded) | International Atomic Energy Agency, jointly sponsored by PAHO and WHO 2018 |
Shares Radiation safety at home after lutetium-177 PSMA or dotatate therapy, International Atomic Energy Agency: Rays of Hope, Lutetium-177 dotatate, Lutetium-177 vipivotide tetraxetan.
Shares Radioiodine therapy (I-131), MIBG imaging and 131I-MIBG therapy, Lutetium-177 dotatate, Radioligand therapy (beta emitters).
Shares Radioactive iodine (I-131), Radioiodine therapy and whole-body iodine scanning.
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Shares Lutetium-177 dotatate, Lutetium-177 vipivotide tetraxetan, Radioligand therapy (beta emitters).
Shares Radioiodine therapy (I-131), Radioiodine therapy and whole-body iodine scanning.
Shares Lutetium-177 dotatate, Lutetium-177 vipivotide tetraxetan, Radioligand therapy (beta emitters).
Shares Low-dose-rate seed brachytherapy.