Radiological protection of family members, carers and the public

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When a patient is exposed to external sources of radiation during diagnostic radiology or radiation therapy, there is no residual radiation in the patient after the procedure, and they pose no radiation risk to people around them. However, when nuclear medicine is used for diagnostic radiology or radiation therapy, protection of family members or the others who provide care to the patient, and the protection of the public the patient may come into contact, should be considered (ICRP Publication 94 Release of Patients after Therapy with Unsealed Radionuclides; ICRP Publication 105 Radiological Protection in Medicine).

For diagnostic nuclear medicine procedures (e.g. bone or myocardial perfusion scans), where the source of radiation is inside the body, radiopharmaceuticals retained in these patients emit radiation but the level of radiation is sufficiently low that these patients do not pose a radiation risk to those around them. These patients are generally discharged immediately after the procedure and instructed that they can carry on their normal daily activities.

For specific therapeutic nuclear medicine (e.g. unsealed source therapy) or radiation oncology (e.g. brachytherapy) procedures, such as 131I therapy for thyroid cancer or some forms of hyperthyroidism, the patient has significant amounts of residual radioactivity in their body that they may pose a slight risk to the others. Thus, radiation safety counselling is required to reduce the exposure of other individuals. Depending on the quantity of radionuclide, the treatment facility may need to hold (e.g. admit) the patient until the quantity is sufficiently reduced through a combination of radioactive decay and biological elimination. In addition, these patients are generally given radiation protection instructions, such as avoiding prolonged close contact with children or pregnant women for a specific period of time post therapy. The radiation safety advice will depend on the burden of underlying disease being treated and the treatment dose of 131I administered.

Radiation safety advice related to implanted therapeutic sources (e.g. brachytherapy) will vary based on the specific radioactive source used. For some sources, such as 125I used for prostate cancer, present very low risk to others. For other sources, such as 192Ir, there may be a radiation risk to others and these patients are usually hospitalised with restricted close contact to others until the source is removed.

Family members and other carers: Exposure to family members or the others who provide care to the patient is defined as medical exposures as there is direct benefits to them, but dose constraints should be established for use in defining the protection policy for visitors to patient and family members at home when a nuclear medicine patient is discharged from hospital. Such groups may include children. ICRP has not previously recommended values for such constraints, but a value of 5 mSv per episode for an adult (i.e. for the duration of a given release of a patient after therapy) is reasonable ([1]). The constraint needs to be used flexibly. For example, higher doses may well be appropriate for the parents of very sick children or for an elderly who would like to take care of his/her sick spouse. Young children, infants, and visitors not engaged in direct comforting or care should be treated as members of the public, who are subject to the public dose limit of 1 mSv/year.

Breastfed babies: In nuclear medicine, varying amounts of radiopharmaceuticals are retained in the patients for varying periods of time. Also, some radiopharmaceuticals can be transferred to breast milk and passed from mother to child during breast feeding. As a result, both the mother, and her breast milk, can be a source of radiation to the baby. Non-urgent tests should be postponed until the breastfeeding period is completed ([2]).

However, most nuclear medicine agents can be handled by providing patient reassurance, educational materials, and instructions on breast milk pumping and storage during a prescribed period of time prior to nuclear medicine treatments. Breast milk can be pumped, frozen and used during a period of time following the treatment. Depending on the specific radiopharmaceutical administered to the mother, guidelines range from interruption in breast feeding for the majority of radiopharmaceuticals, to interruption for a prescribed period of time, to total cessation of breastfeeding ([3]). It is important to consult with a nuclear medicine specialist before ordering a diagnostic nuclear medicine procedure for breastfeeding patients. This will help to provide the information necessary to prepare the patient (e.g. the need to pump breasts, store pumped milk for prescribed decay periods etc.).

131I (half-life of 8 days) is one of the few radioactive agents that deserves special attention. 131I is used for both diagnostic and therapeutic thyroid procedures. Even small amounts of 131I as are used in thyroid uptake studies, are excreted into breast milk and are sufficient to have an adverse effect on the baby’s thyroid function. When 131I is used, breastfeeding should be terminated.

The public: Public access to hospitals and radiology rooms is restricted, but it is more open than is common in industrial and research laboratory operations. There are no radiological protection grounds for imposing restrictions on public access to non-designated areas. Due to the limited duration of public access, an access policy can be adopted for supervised areas if this is of benefit to patients or visitors and there are appropriate radiological protection safeguards. Public access to controlled areas with high-activity sources (e.g. brachytherapy and other therapy sources) should be limited to patients’ visitors, who should be advised of any restrictions on their behaviour.

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