RT 217 - Radiation Protection Lecture 1 PDF

RT 217 – RADIATION PROTECTION LECTURE 1: INTRODUCTION TO RADIATION PROTECTION RADIATION Stochastic Effects  is kinetic energy that moves from one place to another in  on...

RT 217 – RADIATION PROTECTION LECTURE 1: INTRODUCTION TO RADIATION PROTECTION RADIATION Stochastic Effects  is kinetic energy that moves from one place to another in  one for which the probability of the effect occurring a form that can be described as waves or particles. increases with increasing absorbed dose, while the severity of the effect is independent of the magnitude of FORMS OF RADIATION the absorbed dose to the affected individuals. Particulate Radiation  an all-or-none response  are subatomic particles that are ejected from the nucleus  assumed to have no dose threshold of atoms at very high speeds.  the induction of stochastic effects is considered to be the  they possess sufficient kinetic energy to be capable of principal effect that may occur following exposure to low causing ionization by direct atomic collision. doses.  has a finite range in matter, and that range depends on For radiation protection purposes, the National Council the particle’s energy. on Radiation Protection and Measurements (NCRP)  no ionization occurs when the subatomic particles are at assumes: rest. That the risk for stochastic effects is proportional to o Alpha particles dose without threshold throughout the range of dose o Beta particles and dose rates of importance in routine radiation o Neutrons protection, and o Protons That the risk accumulates linearly with dose. When Electromagnetic Radiation higher doses are received acutely, such as in accidents,  photon radiation loses intensity with distance but more complex (nonlinear) dose-risk relationships may theoretically never reaches zero. apply. o Ionizing radiation RADIATION PROTECTION o Non-ionizing radiation  may be defined simply as effective measures employed CLASSIFICATION OF EFFECT FROM IONIZING by radiation workers to safeguard patients, personnel, RADIATION EXPOSURE and the general public from unnecessary exposure to Somatic Effects ionizing radiation.  may become evident in the irradiated individual.  the specific objectives of radiation protection are:  not usually to be expected in individuals exposed in the o to prevent the occurrence of clinically significant course of their work in the medical environment. radiation-induced deterministic effects by  among the somatic effects of radiation are skin adhering to dose limits that are below the erythema, cataracts, and radiation-induced malignancies. apparent threshold levels; and Genetic Effects o to limit the risk of stochastic effects to a reasonable level  do not produce any significantly observable effect in the exposed individual, but may appear in the descendants TYPES OF EXPOSURE SITUATIONS of the exposed individual. Planned Exposure Situations  it is unlikely that any worker in the medical environment  are situations involving the deliberate introduction and would be exposed to ionizing radiation at a level high operation of sources. enough to cause the transmission of appreciable genetic Emergency Exposure Situations effects.  are situations that may occur during the operation of a SERIOUS RADIATION-INDUCED EFFECTS OF planned situation, or from a malicious act, or from any CONCERN IN RADIATION PROTECTION other unexpected situation, and require urgent action in Deterministic Effect order to avoid or reduce undesirable consequences.  one that increases in severity with increasing radiation Existing Exposure Situations dose above a threshold dose.  are exposure situations that already exist when a  occurs only after relatively large doses, but the threshold decision on control has to be taken, including prolonged dose and the severity of the effects may be influenced by exposure situations after emergencies. individual susceptibility and other factors. PAMENIANO 1  CATEGORIES OF EXPOSURE FUNDAMENTAL PRINCIPLES OF RADIOLOGICAL Occupational Exposures PROTECTION  all radiation exposure of workers incurred as a result of The Principle of Justification their work.  any decision that alters the radiation exposure situation Public Exposures should do more good than harm.  all exposures of the public other than occupational  there are two different approaches to applying the exposures and medical exposures of patients. principle of justification in situations involving Medical Exposures of Patients occupational and public exposure, which depend upon whether or not the source can be directly controlled.  occurs in diagnostic, interventional, and therapeutic o The introduction of new activities where procedures. radiological protection is planned in advance CATEGORIES OF EXPOSED INDIVIDUALS and the necessary actions can be taken on the Workers source  as any person who is employed, whether full time, part o Exposures can be controlled mainly by action to time, or temporarily, by an employer and who has modify the pathways of exposure and not by recognized rights and duties in relation to occupational acting directly on the source. Examples are radiological protection. existing exposure situations and emergency  for the exposure of pregnant or breastfeeding workers, exposure situation. additional controls have to be considered to protect the The principle of justification applies at three levels in embryo/fetus. the use of radiation in medicine:  exposures to cosmic radiation be part of occupational The use of radiation in medicine is accepted as doing exposure in the operation of commercial jet aircraft and more good than harm to the patient. space flight. The only practical regulatory measures were A specified procedure with a specified objective is controlling individual exposure through the control of defined and justified. flying time and route selection. The application of the procedure to an individual Classification of Areas of Work: patient should be justified. Controlled areas Unjustified Exposures: o a defined area in which specific protection Increasing, by deliberate addition of radioactive measures and safety provisions are, or could substances or by activation, the activity of products. be, required for controlling normal exposures Radiological examination for occupational, health or preventing the spread of contamination insurance, or legal purposes undertaken without during normal working conditions, and reference to clinical indications. preventing or limiting the extent of potential Medical screening of asymptomatic population groups exposures. involving radiation exposure. o a controlled area is often within a supervised area, but need not be The Principle of Optimization of Protection Supervised areas  the likelihood of incurring exposures, the number of o working conditions are kept under review but people exposed, and the magnitude of their individual special procedures are not normally needed. doses should all be kept as low as reasonably achievable. Public  the process of optimization of protection is intended for application to those situations that have been deemed to  any individual who receives an exposure that is neither be justified and applies to all three exposure situations. occupational nor medical.  optimization of protection is not minimization of dose. Patients Cardinal Principles in Optimizing Occupational  an individual who receives an exposure associated with a Exposure to Radiation: diagnostic, interventional, or therapeutic procedure. Shielding Time Distance PAMENIANO 2  Levels of Radiological Protection:  absorbed doses below 100 mGy to the embryo/fetus emphasizes the primary importance of the source- should not be considered a reason for terminating a related approach, because action can be taken on a pregnancy. source to assure the protection of a group of EXPOSURE OF CARERS AND COMFORTERS individuals from that source. OF PATIENTS considers that the source-related principle of  young children and infants, as well as visitors not optimization below the constraint or reference level is engaged in direct care or comforting, should be treated the most effective tool for protection, whatever the as members of the public for radiological protection situation. purposes. o dose constraint (planned exposure situations)  for individuals directly involved in comforting and caring, o risk constraint (potential exposures) other than young children and infants, a dose constraint o reference level (emergency and existing of 5 mSv per episode (i.e., for the duration of a given exposure situations) release after therapy) is reasonable. in the specific case of planned exposure situations,  the thyroid gland of persons under the age of 15 is more individual-related restrictions are referred as dose radiosensitive than that of adults, so that particular care limits. should be taken to avoid the contamination of infants, diagnostic reference levels are used in medical imaging children, and pregnant women from patients treated to indicate whether, in routine conditions, the levels of with radioiodine. patient dose from, or administered activity for a specified imaging procedure are unusually high or low VOLUNTEERS FOR BIOMEDICAL RESEARCH for that procedure.  the exposure of all volunteers in biomedical research The Principle of Application of Dose Limits under the category of medical exposure.  radiation exposure of pregnant females as subjects in Type of Limit Occupational Public biomedical research is not specifically prohibited. Effective Dose 20 mSv per year, 1 mSv in a year However, their involvement in such research is very rare averaged over 5 years and should be discouraged unless pregnancy is an Annual equivalent dose in: integral part of the research. Lens of the eye 150 mSv 15 mSv Skin 500 mSv 50 mSv Hands and feet 500 mSv -  the total dose to any individual from regulated sources in planned exposure situations should not exceed the appropriate limits recommended.  NCRP (1993) defines an annual Negligible Individual Dose (NID) that establishes a boundary below which the dose can be dismissed from consideration and set the annual NID at 0.01 mSv effective dose. EXPOSURE OF PREGNANT PATIENTS  the feasibility and performance of medical exposures during pregnancy require specific consideration owing to the radiation sensitivity of the developing embryo/fetus.  higher doses such as those involved in therapeutic procedures have the potential to result in developmental harm.  almost always, if a diagnostic radiology examination is medically indicated, the risk to the mother of not doing the procedure is greater than the risk of potential harm to the embryo/fetus. However, some procedures and some radiopharmaceuticals that are used in nuclear medicine can pose increased risks to the embryo/fetus.  cancers that are remote from the pelvis can usually be treated with radiation therapy. PAMENIANO 3