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医療分野での患者の家族が受ける放射線を、医療での放射線利用に伴う放射線曝露に分類し、線量拘束値を利用した放射線防護を行うとしています。

IAEA GSR part 3

The system of protection and safety

1.15. The optimization of protection and safety, when applied to the exposure of workers and members of the public, and carers and comforters of patients undergoing radiological procedures, is a process for ensuring that the likelihood and magnitude of exposures and the number of individuals exposed are as low as reasonably achievable, with economic, societal and environmental factors taken into account. This means that the level of protection would be the best possible under the prevailing circumstances. Optimization is a prospective and iterative process that requires both qualitative and quantitative judgements to be made.

1.30. Dose constraints are used in optimization of protection and safety for carers and comforters and for volunteers subject to exposure as part of a programme of biomedical research.

i For medical exposure, the dose constraint is a source related value used in optimizing the protection of carers and comforters of patients undergoing radiological procedures, and the protection of volunteers subject to exposure as part of a programme of biomedical research.

Requirement 34: Responsibilities of the government specific to medical exposure

3.149. The government shall ensure that, as a result of consultation between the health authority, relevant professional bodies and the regulatory body, the following are established:
(a) Dose constraints, to enable the requirements of paras 3.173 and 3.174, respectively, to be fulfilled for:
(i) Exposures of carers and comforters(40);

(#40) The selection of constraints for carers and comforters is a complex process in which a number of factors have to be taken into account, such as the age of the individual and for a woman the possibility of her being pregnant.

3.153. 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. Registrants and licensees shall ensure that the requirements specified in para. 3.173 are fulfilled for the optimization of protection and safety for any radiological procedure in which an individual acts as a carer or comforter.

Requirement 37: Justification of medical exposures
Relevant parties shall ensure that medical exposures are justified.
3.155. Medical exposures shall be justified by weighing the diagnostic or therapeutic benefits(43) that they are expected to yield against the radiation detriment that they might cause, with account taken of the benefits and the risks of available alternative techniques that do not involve medical exposure.

(#43)
The diagnostic or therapeutic benefit that medical exposures are expected to yield may not necessarily be to the person exposed. For patients, this is clearly the case, but for exposures in biomedical research the benefit is expected to be for biomedical sciences and for future health care. Similarly, the benefit for carers and comforters might be, for example, the successful performance of a diagnostic procedure on a child.

Dose constraints

3.173. Registrants and licensees shall ensure that relevant dose constraints (para. 3.149(a)(i)) are used in the optimization of protection and safety in any radiological procedure in which an individual acts as a carer or comforter.

DEFINITIONS

carers and comforters

Persons who willingly and voluntarily help (other than in their occupation) in the care, support and comfort of patients undergoing radiological procedures for medical diagnosis or medical treatment.

medical exposure

Exposure incurred by patients for the purposes of medical or dental diagnosis or treatment; by carers and comforters; and by volunteers subject to exposure as part of a programme of biomedical research.

IAEA SSG-46

SCOPE

1.13. This Safety Guide provides recommendations for ensuring radiation protection and safety of radiation sources with regard to patients, workers, carers and comforters, volunteers in biomedical research and the public in medical uses of ionizing radiation.

TYPES OF EXPOSURE SITUATION AND CATEGORIES OF EXPOSURE

2.5. Medical uses of ionizing radiation involve all three categories of exposure: occupational exposure for those involved in the performance of radiological procedures; medical exposure, primarily for the patients undergoing the radiological procedures, but also for carers and comforters and for volunteers subject to exposure as part of a programme of medical research; and public exposure for members of the public, such as in waiting rooms.

Optimization of protection and safety

2.13. The optimization of protection and safety, when applied to the exposure of workers and of members of the public, and of carers and comforters of patients undergoing radiological procedures, is a process for ensuring that the magnitude and likelihood of exposures and the number of individuals exposed are as low as reasonably achievable, with economic, societal and environmental factors taken into account. This means that the level of protection and safety would be the best possible under the prevailing circumstances.
2.16. Dose constraints are used in the planning stage in the optimization of protection and safety. Dose constraints are applicable for occupational exposure and for public exposure in medical uses of ionizing radiation. Dose constraints are also used in the optimization of protection and safety for carers and comforters and for volunteers subject to exposure as part of a programme of biomedical research.

Dose limits

2.21. Dose limits apply to occupational exposure and public exposure arising from any use of ionizing radiation. Schedule III of GSR Part 3 [3] sets out these dose limits, which are reproduced here for convenience (see Box 1). Dose limits do not apply to medical exposure (i.e. exposure of patients, carers or comforters, and volunteers as part of a programme of biomedical research).

2.47. In addition to patients, two other groups of people that can incur medical exposure are carers and comforters, and volunteers in biomedical research. Since it is medical exposure, neither of these groups is subject to dose limits for the exposures incurred. Instead, reliance is placed on the use of dose constraints as a means for ensuring that optimization of protection and safety takes place (see para. 2.16). For both of these groups of people, the government, through consultation with the health authority, the relevant professional bodies and the radiation protection regulatory body, has the responsibility to ensure that dose constraints are established.
2.48. For carers and comforters, the usual approach is to apply dose constraints on an episode by episode basis — that is, the dose constraint applies to the cumulative exposure of the carer or comforter over the duration of that person giving care and comfort to a patient. In the case of a parent assisting with his or her child undergoing a diagnostic X ray procedure, the episode is the time in which the X rays are being produced, which is extremely short. In the case of a carer or comforter for a person having undergone treatment with radiopharmaceuticals, the episode will last several days until the radionuclide has decayed to negligible levels. Consideration should be given to the cumulative dose of a carer or comforter acting in this role for several distinct episodes. In such cases, a dose constraint per annum may be used in addition to an episode based dose constraint.
2.49. In setting dose constraints for carers and comforters, consideration should be given to the age of the individual and the possibility of pregnancy. A particular issue is that of children in this role. The definition of a carer or comforter includes that the person “willingly and voluntarily” helps in this role. It could be argued that young children might not understand such concepts. Nonetheless, it is reasonable and likely that the children of a parent undergoing treatment would want to provide and receive comfort. The framework for radiation protection and safety should accommodate such wishes. A pragmatic approach is often taken, whereby children in this role are effectively treated as members of the public and their medical exposure is constrained to an effective dose of 1 mSv per episode. A pregnant carer or comforter presents a similar situation, and consideration should be given to the embryo or fetus. The same approach of constraining the effective dose to the embryo or fetus to 1 mSv per episode is often taken. For an adult carer or comforter, a value of dose constraint commonly used is 5 mSv effective dose per episode. For elderly persons, more lenient dose constraints may be used. In any of these cases, flexibility may need to be applied with respect to the dose constraint.

検討例

第３回医療放射線の適正管理に関する検討会

関連用語

線量限度