L7 Radiation Protection Principles PDF

RADIATION PROTECTION PRINCIPLES  OUTLINE 6. Principles of Radiation Protection. 6.1 Understanding the potential risks and benefits of medical exposure. 6.1.1 Risks. 6.1.2 Benefit. 6.2 Principles of radiation protection. 6.2.1 Justification. 6.2.2 Opt...

RADIATION PROTECTION PRINCIPLES  OUTLINE 6. Principles of Radiation Protection. 6.1 Understanding the potential risks and benefits of medical exposure. 6.1.1 Risks. 6.1.2 Benefit. 6.2 Principles of radiation protection. 6.2.1 Justification. 6.2.2 Optimization. 6.2.3 Dose limit. 6.3 Radiation protection actions. 6.3.1 Shielding. 6.3.2 Time. 6.3.3 Distance. 7. Radiation Protection Rules and Regulations. 7.1 International Commission in Radiological Protection (ICRP). 7.2 Biological Effects of Ionizing Radiation Committee (BEIR). 7.3 Atomic Energy Licensing Act 1984 (Act 304). 7.4 Malaysian Standard (MS838) : Code of Practice for Radiation Protection (Medical X-ray Diagnosis).  What is radiation protection? Series of actions or measures that need to be taken in order to reduce the risks of radiation injury to patient, personnel, and public.  Objective of radiation protection “To prevent the occurrence of deterministic effects by keeping doses below relevant thresholds, and to ensure that all reasonable steps are taken to reduce the induction of stochastic effects” ( ICRP,1991)  “To prevent the occurrence of serious radiation- induced conditions (acute and chronic deterministic effects) in exposed persons and to reduce stochastic effects in exposed persons to a degree of acceptable in relation to the benefits to the individual and to society from the activities that generate such exposure” (NCRP,1993)  Principles of radiation protection As recommended by ICRP (1991): o Justification o Optimization o Dose limit  Justification No practice involving exposures to radiation should be adopted unless it produces sufficient benefit to the exposed individuals or to society to offset the radiation detriment it causes. Should take into consideration: o Why the procedure is needed? o Which modality? evidence-based medicine o Type of patient? o Type of studies/procedures? BENEFIT VS. RISKS  Optimization The dose given to patient should be kept as minimum as possible without compromising with the diagnostic or therapeutic value of the procedure. Associated with ALARA. Takes into consideration of social and economic factor How to achieve optimization in radiation protection? o Proper education and training. o Follow guidelines and recommendation by authorities.  Understanding the factors that affect dose, dose reduction methods, and shielding requirements. REFLECT WITH YOUR CLINICAL PRACTICE / EXPERIENCE !  Dose limit To ensure that no individual is exposed to radiation risks that are judged to be unacceptable from radiological practices in any normal circumstances. Deals with the establishing annual dose limits for occupational exposures, public exposures and exposures to embryo and fetus. Do not include medical exposures and natural background radiation  Occupational, medical and public exposures Occupational exposure All exposures of workers incurred: o In the course of their work, with the exception of exposures excluded from the standards o Exposures from practices or sources exempted by the standards  Occupational, medical and public exposures Medical exposure: Exposure incurred by patients o as part of their own medical or dental diagnosis or treatment; o by persons, other than those occupationally exposed, knowingly while voluntarily helping in the support and comfort of patients; o by volunteers in a programme of biomedical research involving their exposure  Occupational, medical and public exposures Public exposure: Exposure incurred by: o Members of the public from radiation sources, o Excluding any occupational or medical exposure and the normal local natural background radiation o But including exposure from authorized sources and practices and from intervention situations.  Annual dose limits: 1. Radiation workers 2. Members of the public 3. Trainees of radiation 4. Planned special exposures 5. Female pregnant workers Annual dose limit for occupational exposure AELB exposure of members of public AELB Dose limit for apprentice and students Application In a calendar year (mSv) Dose limit for the whole body exposure 1 Average dose for lens of the eyes 50 Equivalent dose to the extremities 150 Equivalent dose to the skin 150 Apprentices and students in radiation work (in a supervised or controlled areas) must not be less than 18 years old. AELB  RADIATION PROTECTION ACTIONS Three general guidelines for controlling exposure to ionising radiation: o SHIELD Shield from radiation sources o TIME Minimising exposure time o DISTANCE Maximising distance from radiation sources RADIATION PROTECTION ACTIONS Shielding Material may be used to attenuate radiation and thus provide shielding against external exposure. Shielding takes into consideration the density and thickness of shielding materials, the quality of radiation. Quality of radiation refers to type of radiation, its energy, the flux and dimension of source.  Barrier thickness incident radiation transmitted radiation RADIATION PROTECTION ACTIONS Attenuation of x-and gamma-rays require the use of high atomic number materials. The most suitable material is lead and iron. In the medium energy range (0.50 – 0.75 MeV) the density of the material is more important than the atomic number. At higher and lower energy ranges, materials of higher atomic number are more effective. RADIATION PROTECTION ACTIONS Comparison - types of radiation and shielding required RADIATION PROTECTION ACTIONS Selection of shield depends on the types of radiation. Alpha particles lose energy rapidly in passage through matter and hence do not penetrate far. No shielding is required against alpha particles. Beta particles do not lose energy so rapidly compared to alpha particles, and are therefore more penetrating. Materials composed of elements of low atomic number such as Perspex and aluminum and thick rubber are most appropriate for the absorbance of beta particles. RADIATION PROTECTION ACTIONS Neutrons are uncharged particles and can penetrate matter considerably. Shields use on neutron is directed towards reducing the energy of the neutrons to levels that can easily be absorbed c Neutron (< 1 MeV) A reduction of the energy of neutron is best accomplished by collisions with atoms of light elements, e.g. hydrogen. c Neutrons (> 1 MeV) Energy of fast neutrons is best reduced using water and paraffin wax. 20 cm of paraffin wax will attenuates 1 MeV fast neutrons by a factor of 10  Maximize and Optimize Shielding Leaded shielding reduces doses to 5% or less! Shielding must be between the patient and the person to be protected If back is to patient, need protection behind individual Coat aprons protect back and help distribute apron weight Everyone in the procedure room must wear a protective apron 27 RADIATION PROTECTION ACTIONS Time Dose = Dose rate x time The longer the exposure time the higher is the dose received and vice versa.  Minimize Exposure Time Everything you do to minimize exposure time reduces radiation dose!! oMinimize fluoro and cine times oWhenever possible, step out of room oStep behind barrier (or another person) during fluoro or cine oUse pulsed fluoroscopy– minimizes time x-ray tube is producing x rays 29  Maximize Distance – Inverse Square Law Radiation dose varies inversely with the square of the distance 3 2 1 2 4 1 6 5 3 4 9 D 8 7 2D 3D If you double your distance from source of x rays, your dose is reduced by a factor of 4, i.e., it is 25% of what it would have been!  Inverse Square Law Helps Protect You Move from 20 cm to 40 cm, or 1 m to 2 m, from patient, dose rate decreased 4X or to 25%!! The patient is the source of scattered radiation!! Do not stand next to patient during fluoro Step back during cine runs 3 2 1 2 4 1 6 5 3 4 9 D 8 7 2D 3D 31  Radiation Protection Systems Distance Reduction of radiation dose inversely proportional the square of the distance or it follows the inverse square law equation. 2 I1 d1 = I2 d2 2 where I1 and I2 are radiation intensities at distances d1 and d2 respectively.  High radiation risk Occupational doses in interventional procedures guided by fluoroscopy are the highest doses registered among medical staff using X-rays. If protection tools and good operational measures are not used, and if several complex procedures are undertaken per day, radiation lesions may result after several years of work.  ICRP report 85 (2001): Avoidance of Radiation Injuries from Interventional Procedures Cataract in eye of interventionalist after repeated use of old x ray systems and improper working conditions related to high levels of scattered radiation. Lecture 7: Occupational 34 exposure and protective devices 0.5 – 2.5 mSv/h 1- 5 mSv/h 2- 10 mSv/h  ) Relevant organizations in RP (ICRP, IAEA and UNSCEAR  Relevant organizations in radiation protection: ICRP, IAEA, UNSCEAR ICRP provides recommendations IAEA establishes standards of safety and provides for the application of the standards UNSCEAR studies the effects of atomic radiation  Relevant organizations in radiation protection: ICRP (I) ICRP (http://www.icrp.org) o In preparing its recommendations, ICRP considers the fundamental principles and quantitative bases upon which appropriate radiation protection measures can be established, while leaving to the various national protection bodies the responsibility of formulating the specific advice, codes of practice, or regulations that are best suited to the needs of their individual countries.  Relevant organizations in radiation protection: ICRP (II) ICRP (http://www.icrp.org) o ICRP offers its recommendations to regulatory and advisory agencies and provides advice intended to be of help to management and professional staff with responsibilities for radiation protection. o While ICRP has no formal power to impose its proposals on anyone, in fact legislation in most countries adheres closely to ICRP recommendations.  Relevant organizations in radiation protection: UNSCEAR United Nations Scientific Committee for the Effects of the Atomic Radiation They elaborate the “UNSCEAR reports” to United Nations General Assembly about use and effects of atomic radiation.  Relevant organizations in radiation protection: IAEA (I) IAEA (http://www.iaea.org) An independent intergovernmental, science and technology-based organization, in the United Nations family, that serves as the global focal point for nuclear cooperation 41  Relevant organizations in radiation protection: IAEA (II) Statutory functions with regard to safety: o to establish standards of safety for the protection of health o to provide for the application of these standards …. at the request of a state  Committee on the Biological Effects of Ionizing Radiation (BEIR V) IN EARLY 1990 a new report on radiation risk estimation was released by the National Research Council (NRC), an agency administered by the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. Report, entitled "Health Effects of Exposure to Low Levels of Ionizing Radiations," was prepared by the NRC's Committee on the Biological Effects of Ionizing Radiations (BEIR) referred to as BEIR V. Mission of the BEIR V is To conduct a comprehensive review of the biological effects of ionizing radiations To provide new estimates of the risks of genetic and somatic effects associated COMPARISON ICRP 60 & ICRP 103  Antara tambahan yang dilakukan ke atas ICRP 103 berbanding ICRP60 adalah: i. Had dos ke atas fetus bagi pekerja perempuan yang disahkan mengandung menurun dalam ICRP 103 berbanding ICRP 60. ii. Had dos bagi petugas perubatan pula ditetapkan kepada 5mSv per episod dan 20mSv/tahun berbanding ICRP 60 yang tidak menetapkan had dos ke atas petugas perubatan. iii. Addition to ICRP103 compare to  GUIDELINES IN MALAYSIA Radioactive Substances Act (1968) ACT 304 MS 838  Radioactive Substances Act (1968) Operators of x-ray machines including medical personnel are required to comply with the requirements of the regulations. This act aimed at licensing the use of x-ray machines and regulating radiological safety. But, it does not provide information on proper procedures and operations of equipment necessary to attain a high standard of performance in x-ray examination.  Act 304: Atomic Energy Licensing Act 1984 This act shall apply throughout Malaysia To provide for the regulation and control of atomic energy, for the establishment of standards on liability for the nuclear damage and for matters connected therewith or related thereto.  Sections included: o Part 1: Preliminary o Part 2: Atomic Energy Licensing Board o Part 3: Control and Licensing o Part 4: Health and Safety o Part 5: Disposal of Radioactive Waste o Part 6: Appeals o Part 7: Powers of Seizures and Arrest Offences and Forfeiture o Part 8: Liability for Nuclear Damage o Part 9: General  MS 838 (Malaysian Standards) MS 838:1985: Code of Practice for Radiation Protection (Medical X-ray Diagnosis) Established by Act of Parliament. Based on various international codes of practice and procedures and local conditions have been taken into considerations. To provide necessary references to the x-ray machine operators, general practitioners, medical officers, radiologists and other medical specialists.  Aim to improve the present x-ray techniques. Private and public sectors are hoped to comply with this code of practice.  Sections included in the code of practice: o Introduction o Radiological safety o Structural shielding and lay-out o Safety and performance requirements of x-ray systems o Records and reports of x-ray systems o Administrative requirements