Radioactive substances have been used in medicine for over 100 years. Today, medical use of radiation is the largest, and a growing, manmade source of radiation exposure. Nuclear medicine has become an important diagnostic and therapeutic specialty, and there are nearly 100 different procedures that provide information about virtually every major organ system in the body.
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) estimated that, worldwide, more than 30 million diagnostic nuclear medicine procedures and nearly 400,000 therapeutic procedures with radiopharmaceuticals are carried out each year (UNSCEAR, 2000). Radioactive iodine was introduced in the 1940s, and although many other radiopharmaceuticals are used in nuclear medicine, iodine-131 continues to be the most important radionuclide.
The use of unsealed radionuclides can result in exposure of other people as well as patients, and there is a need for guidance regarding the radiological protection of members of the public, relatives, and caregivers from such exposures. The International Commission on Radiological Protection (ICRP) has not provided recommendations on the criteria to follow regarding the release of patients from hospital after therapy with unsealed radionuclides, or on activity levels that require hospitalisation of the patient. Instead, the Commission has relied upon the dose limit of 1 mSv/year for the public, and the dose constraint of 5 mSv/episode for relatives, visitors, and caregivers (ICRP, 1991(ICRP, , 1996)). These recommendations have been interpreted differently in various countries, and the dose constraint has often been inappropriately interpreted as a rigid annual dose limit.
The decision to hospitalise or release a patient should be determined on an individual basis, and should consider factors such as the residual activity in the patient, the patientÕs wishes, occupational and public exposures, family considerations, cost, and environmental aspects. Committee 3 established a Task Group in 1999 to review this topic. This report is one of a set of documents being developed by ICRP Committees to advise the Commission on the formulation of its next recommendations for radiological protection.
This report covers both diagnostic and therapeutic procedures, but focuses on iodine-131, which is the major source of exposure to staff and relatives from therapy with unsealed radionuclides. Precautions for the public are rarely required after diagnostic procedures, but doses to the public and relatives may need to be limited after some therapeutic procedures.