IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Part VIII:Medical Exposures in Radiotherapy Justification of Medical Exposure & evaluation of detriment Lecture 3 : Justification of Medical Exposure & evaluation of detriment IAEA Post Graduate Educational Course on Radiation Protection and Safe Use of Radiation Sources Module 2 – Justification of Medical Exposures

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Scope To understand the criteria for justification of medical exposuresTo understand the criteria for justification of medical exposures Need to identify alternative techniques.Need to identify alternative techniques. Understand the method of evaluation of DetrimentUnderstand the method of evaluation of Detriment

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Justification of a Practice 1.Adoption of new practices or the continuation of existing practices must take into consideration the risks of radiation effects as a result of that practice. 2.A practice which involves exposures or potential exposures should only be adopted if it is likely to produce sufficient benefit to the individual or to society to outweigh the detriment or harm to health it may cause.

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Types Of Exposure Medical exposure: It is the exposure of a person as part of a medical diagnosis or treatment.Medical exposure: It is the exposure of a person as part of a medical diagnosis or treatment. –The exposure is controlled as for occupational exposure but is included as part of the diagnosis or treatment plan, not as part of a radiation protection system. Public exposure: It is the exposure of a person by means other than occupational or medical exposure.Public exposure: It is the exposure of a person by means other than occupational or medical exposure. –The controls should be applied at the source. They should only be applied to the environment or to the individuals if source controls are not effective, as, for example, in a serious accident such as Chernobyl.

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Justification of Medical Exposures Medical exposures should be justified by weighing the therapeutic benefits they produce against the radiation detriment they might cause, taking into account the benefits and risks of available alternative techniques that do not involve medical exposureMedical exposures should be justified by weighing the therapeutic benefits they produce against the radiation detriment they might cause, taking into account the benefits and risks of available alternative techniques that do not involve medical exposure BSS –Appendix II

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Criteria for Justification of Medical exposure In justifying a type of diagnostic examination the relevant guidelines will be taken into account, such as those established by the WHOIn justifying a type of diagnostic examination the relevant guidelines will be taken into account, such as those established by the WHO Mass screening of population groups involving medical exposure is deemed to be not justified unless the expected advantages for the individual examined or for the population as a whole are sufficient to compensate for the economic and social costs, including the radiation detriment.Mass screening of population groups involving medical exposure is deemed to be not justified unless the expected advantages for the individual examined or for the population as a whole are sufficient to compensate for the economic and social costs, including the radiation detriment.

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Exposure for Medical Research The exposure of humans for medical research is deemed to be not justified unless it isThe exposure of humans for medical research is deemed to be not justified unless it is –A) in accordance with the provisions of the Helsinki Declaration and follows the guidelines for its application prepared by Council for International Organizations of Medical Sciences (CIOMS) and WHO and –B) subject to the advice of an Ethical Review Committee and to applicable national and local regulations. -BSS Appendix II

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment An example of unjustified - Exposure for theft detection Radiological examinations for theft detection purposes are deemed to be not justified; should they nonetheless be conducted, they shall not be considered medical exposure but shall be subject to the requirements for occupational and public exposure of the standardsRadiological examinations for theft detection purposes are deemed to be not justified; should they nonetheless be conducted, they shall not be considered medical exposure but shall be subject to the requirements for occupational and public exposure of the standards

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Un Justified exposure in Radiation Therapy Before resorting to radiation therapy – alternative techniques such as surgery or chemotherapy to be tried.Before resorting to radiation therapy – alternative techniques such as surgery or chemotherapy to be tried. ExampleExample –Keliod’s – a benign lesion – Radiation should not be the first choice, alternate should be tried before resorting to radiation.

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment THE IAEA BASIC SAFETY STANDARD 1.In 1990, the Inter-Agency Committee on Radiation Safety (IACRS) was established 2.Aim was to further promote consistency in the practical application of radiation protection. 3.As a result, a detailed document was prepared called the International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sourcescalled the International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Motive of Basic Safety Standards (BSS) 1.BSS is intended to serve as a practical guide for the design and implementation of an effective radiation protection program. 2.BSS contains standards which are based on the principles of radiation protection recommended by the ICRP. 3.Like the ICRP recommendations, the Basic Safety Standards are for guidance only and not a legal text. 4.The standards are designed such that they may be incorporated into the legislation of individual countries as required to form a practical basis for the specific radiation protection needs of that country. 4.The standards are designed such that they may be incorporated into the legislation of individual countries as required to form a practical basis for the specific radiation protection needs of that country.

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment ICRP 26 ICRP 60 System of Dose Limitation System of Radiological Protection International Commission on Radiation Protection - Recommendations broader outlookbroader outlook possibility of accidentspossibility of accidents potential for accidental exposurespotential for accidental exposures

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Types Of Exposure The ICRP refers to three types of exposure: Occupational exposure: It is the exposure of a person mainly as a result of the work they perform.Occupational exposure: It is the exposure of a person mainly as a result of the work they perform. It can be controlled at three levels;It can be controlled at three levels; –at the source (e.g. shielding); –in the environment (e.g. ventilation); and – at the level of the worker (e.g. good work practices, protective clothing).

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Principles of Radiation Protection Radiation Protection System Justification Benefit > Risk Optimization ALARA Limitation Numerical dose limits The system of radiation protection recommended by the ICRP in Publication 60 is based on three major principles justification, optimization, and dose limitationThe system of radiation protection recommended by the ICRP in Publication 60 is based on three major principles justification, optimization, and dose limitation It is important that none of the principles should be used on their own. An effective radiological protection system should use the three principles to ensure that all radiation doses are kept as low as possible

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Evaluation of Detriment How does the risk of handling ionising radiation sources compare with the occupational risk in other industries?How does the risk of handling ionising radiation sources compare with the occupational risk in other industries?

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Probability of 1 in a million chance of death 1.5 cigarettes smoked1.5 cigarettes smoked 80 km driven in a car80 km driven in a car 420 km in a plane420 km in a plane 2 weeks work in a factory2 weeks work in a factory 20 minutes as a 60 year old20 minutes as a 60 year old 9 hours as a 30 year old9 hours as a 30 year old

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Probability of 1 in a million chance of death 6 minutes canoeing6 minutes canoeing 90 second rock climbing90 second rock climbing Eating 500 g peanut butterEating 500 g peanut butter Eating 100 BBQ steaksEating 100 BBQ steaks 0.02 mSv acute ionizing radiation exposure0.02 mSv acute ionizing radiation exposure

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Classification of Radiation effects Somatic & Hereditary Effects Somatic effects the health of the exposed individualSomatic effects the health of the exposed individual Hereditary effects occur in the descendants of exposed individualsHereditary effects occur in the descendants of exposed individuals

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Radiation effects Stochastic & Deterministic effects Stochastic effects: Are effects for which the probability of an effect occurring rather than its severity is regarded as a function of dose with no threshold, e.g. range of solid tumours as well as leukaemia Non-Stochastic effects (Deterministic):Are those which become evident after a large dose. There is a threshold below which the effects do not occur, e.g. erythema - reddening of the skin (3 Sv)..

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Radiation Effects Stochastic effectsStochastic effects –Pertains to Random Process –No Threshold dose –Severity independent of dose –Probability depends on dose –Late effects –Example CarcinogensisCarcinogensis Genetic effectGenetic effect

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Examples of Stochastic Effects

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Radiation effects Deterministic (Non stochastic) effect:Deterministic (Non stochastic) effect: –Has a threshold dose –Severity depends on dose –Early effects –Example CataractCataract Erythema (reddening of skin)Erythema (reddening of skin) Epilation (loss of hair)Epilation (loss of hair)

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Individual Dose Limits The ICRP recommends that the exposure of individuals should be subject to dose limits.The ICRP recommends that the exposure of individuals should be subject to dose limits. Criteria for dose limits Criteria for dose limits –No unacceptable risk –Prevention of Deterministic effect –Minimization of Stochastic effects For members of the public, dose limit is approximately the same as the average dose from natural sources, excluding radon, at sea level.For members of the public, dose limit is approximately the same as the average dose from natural sources, excluding radon, at sea level. Dose limits apply to exposures resulting from practices, and exclude medical exposures and natural backgroundDose limits apply to exposures resulting from practices, and exclude medical exposures and natural background

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Effective dose E The “Effective dose” (E) assesses risk by modifying the dose equivalent using a tissue weighting factor w T provided in ICRP - 60.The “Effective dose” (E) assesses risk by modifying the dose equivalent using a tissue weighting factor w T provided in ICRP The Effective dose is given byThe Effective dose is given by E =  w T. H T E =  D R,T W R W T w T is the tissue weighting factor, independent of the radiationw T is the tissue weighting factor, independent of the radiation Corrects for Volume & Radio sensitivity of tissue irradiated - Units are Sv (usually stated in mSv) Corrects for Volume & Radio sensitivity of tissue irradiated - Units are Sv (usually stated in mSv)

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Effective Dose ICRP - 60 Tissue Weighting Factors (W T ) Gonads Gonads Bone marrow (red) Bone marrow (red) Colon Colon Lung Lung Stomach Stomach Bladder Bladder Breast Breast Liver Liver Esophagus Thyroid Skin Bone surface Remainder TOTAL General population, all ages, both genders.

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Summary of Radiation Quantities Exposure:Exposure: Dose (D)Dose (D) Radiation Weighting factorsRadiation Weighting factors Dose Equivalent (H)Dose Equivalent (H) Tissue Weighting FactorsTissue Weighting Factors Effective DoseEffective Dose Linear Energy TransferLinear Energy Transfer

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Equivalent Dose Dose averaged over tissue or organDose averaged over tissue or organ The Equivalent Dose H T in tissue T H T = w R. D T,R D is in Gy H T is in Sv (Sievert) – –w R is the radiation weighting factor, independent of the tissue (Similar to the Quality Factor) w T is the tissue weighting factor, independent of the radiation

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment The Optimization of Protection Individual doses, the number of people exposed and the likelihood and magnitude of potential exposures should all be kept As Low As Reasonably Achievable, economic and social factors being taken into account.Individual doses, the number of people exposed and the likelihood and magnitude of potential exposures should all be kept As Low As Reasonably Achievable, economic and social factors being taken into account. This is known as the ALARA principle. It means that radiation sources and installations should be provided with the best practical protection and safety measures possible, with all social and economic factors being considered. This is known as the ALARA principle. It means that radiation sources and installations should be provided with the best practical protection and safety measures possible, with all social and economic factors being considered. Protection and safety should be optimized.Protection and safety should be optimized.

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Radiation Weighting Factors

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Summary of Radiation Quantities Relationships :1 C/kg = 3881 R (air) 1 Gy = 100 rad ; 1 Sv = 100 rem

IAEA Rad Safety course Justification of Medical Exposure & evaluation of detriment Part VIII Justification of Medical Exposure & evaluation of detriment Summary Radiation should be used only if it has advantages over means of treatmentRadiation should be used only if it has advantages over means of treatment The criteria for justification should be considered for the use of RadiationThe criteria for justification should be considered for the use of Radiation The detriment should be evaluated for the organs at riskThe detriment should be evaluated for the organs at risk