For family members, caregivers and the public
When a patient is exposed to external sources of radiation during diagnostic radiology or Radiation therapy, there is no residual radiation remained in the patient after the procedure, and the patient poses no radiation risk to family members or the others who provide care to the patient, and the general public the patient may come into contact. However, when nuclear medicine is used for diagnostic radiology or Radiation therapy, protection of family members, other carers and the public, should be considered as the patient may remain “radioactive” for some time following the administration; the radiopharmaceuticals administered to the patient would need some time to physically decay or be biologically eliminated (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), the amounts of radiopharmaceuticals administered to the patients are typically small and consequently the amounts of radiopharmaceuticals retained in these patients and the levels of radiation emitted are low as well. These patients are generally discharged immediately after the procedure and instructed that they can carry on their normal daily activities. These patients do not pose a radiation risk to those around them.
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 may pose some risks to the others, if they are released shortly after the treatment procedure. To reduce such risks, the patient is usually admitted for a period of time, or discharged if radiation safety concerns are adequately met (e.g. lives alone with restrictions on human contact for a period of time) until the radiopharmaceutical retained in the body is sufficiently reduced through a combination of radioactive decay and biological elimination. In addition, these patients are generally instructed to avoid prolonged close contact with children or pregnant women for a specific period of time following release.
In nuclear medicine, varying amounts of radiopharmaceuticals are retained in the body 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 a baby. So, non-urgent nuclear medicine tests should be postponed until the breast-feeding period is completed. Depending on the specific radiopharmaceutical administered, guidelines range from no interruption in breast feeding for the majority of radiopharmaceuticals, to interruption for a prescribed period of time, to total cessation of breast feeding. A nuclear medicine specialist should be consulted prior to the administration of radiopharmaceuticals to breast feeding patients. In addition, if a radiopharmaceutical is administered to a pregnant woman, it may pass through the placental barrier and present a possible risk to the unborn child.
131I deserves special attention. 131I is used for both diagnostic and therapeutic thyroid procedures. Even small amounts of 131I (physical half-life of 8 days), 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 and induce hypothyroidism. When 131I is used, breastfeeding should be terminated.