Radiation Protection Lecture Notes PDF

Radiation protection Chapter 16  Justification for Radiation Protection Ionization The production of charged particles Biologic damage potential Somatic effects Carcinogenesis Embryologic effe...

Radiation protection Chapter 16  Justification for Radiation Protection Ionization The production of charged particles Biologic damage potential Somatic effects Carcinogenesis Embryologic effects Cataractogenesis Life-span shortening Genetic effects Mutations Types of Radiation Alpha particles Beta particles Negatron vs. positron X-rays and gamma rays Types of Ionizing Radiation Types of Radiation Charge Atomic Mass Origin Number Alpha particles (α) +2 4 Nucleus Beta particles Negatron (β–) –1 0 Nucleus Positron (β+) +1 0 Nucleus Neutrinos (ν) 0 0 Nucleus X-rays 0 0 Electron shells Gamma rays (γ) 0 0 Nucleus  Sources of Radiation Natural Man-made ▪ Cosmic rays ▪ Medical procedures ▪ Terrestrial radiation ▪ Consumer products Radon ▪ Nuclear radiation ▪ Internal radiation EXPOSURE A measure of the ionization caused by the absorption of x-rays in a specified mass of air at the point of interest Units ▪ Roentgen ▪ Coulomb/kilogram Conversion factor 1 R = 2.581 x 10-4 C/kg Absorbed Dose The amount of energy transferred to the interacting medium per unit mass of the medium by ionizing radiation Units ▪ Rad ▪ Gray Conversion factor 1 Gy = 100 rad Equivalent Dose ▪ The amount of biologic harm to tissue caused by exposure to ionizing radiation ▪ Quality factor Accounts for the difference in biologic effect of each type of ionizing radiation Equivalent Dose ▪ Quality factors X-rays, gamma rays, and electrons = 1 Thermal neutrons = 5 High-energy photons = 10 Fast neutrons and alpha particles = 20 ▪ Units Rem Sievert ▪ Conversion factor 1 Sv = 100 rem Radioactivity ▪ The emission of energy in the form of electromagnetic radiation or energetic particles ▪ Units Curie Becquerel ▪ Conversion factor 1 Ci = 3.7 x 1010 Bq The main objective of radiation protection 1. To prevent clinically significant radiation-induced tissue reactions by adhering to dose limits that are below the apparent or practical dose threshold 2. To limit the risk of stochastic effects (cancer and heritable effects) to a reasonable level in relation to societal needs, values, and benefits gained Principles of radiation protection 1- Justification 2- ALARA (As Low As Reasonably Achievable. 3- Limitation. Comparable Risk ▪ The National Council on Radiation Protection and Measurement (NCRP) has attempted to compare the risk of injury from ionizing radiation to the risk of injury in other occupations ▪ Safe industry An occupation with a risk of accidental death of 1 in 10,000 per year NIRL ▪ Negligible individual risk level Also known as de minimis dose ▪ A level of effective dose that can be dismissed as insignificant and below which further efforts to improve radiation protection are not justified 0.001 rem (0.01 mSv) per year Risk of death for 1 in 10,000,000 people General Rules of Personnel Monitors ▪ Never share badges or wear ▪ Do not wear your badges another person’s badges when receiving a ▪ Do not intentionally expose medical badges to radiation x-ray or other medical ▪ Report accidental badge radiation treatment exposures or contaminations ▪ Store badges in a safe place ▪ Do not take badges to any other institution  International Origins of Radiation Protection Second International Congress of Radiology ICXRP International Committee on X-Ray and Radium Protection ICRP International Commission on Radiological Protection ICRU International Commission on Radiation Units & Measurements Origins of Radiation Protection in the United States Efforts in the United States ▪ ACXRP Advisory Committee on X-Ray and Radium Protection ▪ NCRP National Council on Radiation Protection & Measurements Radiation Protection Organizations ▪ UNSCEAR United Nations Scientific Committee on the Effects of Atomic Radiation ▪ BEIR Biological Effects of Ionizing Radiation ▪ ICRP International Commission on Radiological Protection Radiation Protection Organizations ▪ NCRP National Council on Radiation Protection & Measurements ▪ EPA Environmental Protection Agency ▪ NRC Nuclear Regulatory Commission Regulatory Agencies ▪ International Commission on Radiological Protection (ICRP) ▪ National Council on Radiation Protection & Measurements (NCRP) ▪ Nuclear Regulatory Commission (NRC) ▪ Consumer-Patient Radiation Health and Safety Act of 1981 ▪ State agencies ICRP Mission “Established to advance for the public benefit the science of radiological protection, in particular by providing recommendations and guidance on all aspects of protection against ionizing radiation” Activities Establishes recommendations Provides advice No jurisdiction to enforce its recommendations NCRP Mission “Seeks to formulate and widely disseminate information, guidance and recommendations on radiation protection and measurements which represent the consensus of leading scientific thinking” Activities Radiation protection watchdog No jurisdiction to enforce its recommendations NRC Mission “To regulate the nation's civilian use of byproduct, source, and special nuclear materials to ensure adequate protection of public health and safety, to promote the common defense and security, and to protect the environment” Activities Develops regulations Licenses users of nuclear materials Oversees operations of facilities using nuclear materials Conducts research NCRP Recommendations Offered in the form of reports ▪ NCRP Report No. 102 ▪ NCRP Report No. 105 ▪ NCRP Report No. 107 ▪ NCRP Report No. 114 ▪ NCRP Report No. 116 NCRP Report No. 105 ▪ Biologic effects and protection against radiation ▪ Regulatory control requirements Designed for general public use ▪ Provides general information on radiation and its uses in medicine A subsequent section provides pertinent job-related information for personnel involved with radiation sources NCRP Report No. 107 ▪ Addresses the implementation of ALARA for occupational exposure of persons working in medicine and dentistry.  NCRP Report No. 116 ▪ Basic radiation protection ▪ Revised tissue/organ weighting factors ▪ Reviews absorbed dose, equivalent dose, radiation weighting factors, and effective dose ▪ Addresses exposure in excess of the limits, limits for unusual occupational situations, guidance for emergency occupational exposure, and remedial action levels for naturally occurring radiation Cardinal Principles of Radiation Protection Time The less time an individual is exposed to radiation, the lower the dose will be Distance Increasing the distance from the source of radiation will dramatically reduce the dose Inverse square law X2 = X1(D1/D2)2 Shielding Most important of all radiation protection principles Practical Radiation Protection Barriers Dose calculation factors ▪ Barrier material ▪ Use ▪ Primary shielding ▪ Workload ▪ Secondary shielding ▪ Occupancy ▪ Mazes and doors ▪ Distance ▪ Transmission Barrier Material ▪ Particle type and energy ▪ Major shielding materials Lead Steel Concrete Barrier Material ▪ Half-value layer (HVL) The thickness of material necessary to reduce the dose or intensity of the beam to half its original value ▪ Tenth-value layer (TVL) The thickness of material necessary to reduce the dose or intensity of the beam to one tenth its original value Primary Shielding Primary ▪ Shields the primary beam ▪ Two forms Internal lead housing Portion of the treatment room designed to absorb the primary beam Secondary Shielding Secondary ▪ Shields leakage and scattered radiation ▪ Protects individuals occupying areas outside areas of high doses Controlled Areas  Areas where the individuals exposed are monitored by a radiation safety program  Dose equivalent limit of 0.1 rem/week or approximately 5 rem/year  Summary ▪ The objectives of radiation protection are to prevent clinically significant tissue reactions by keeping doses below the practical threshold and to limit the risk of stochastic effects (cancer and heritable effects) to a reasonable level in relation to societal needs, values, and benefits gained. ▪ Justification is one of the basic principles of radiation protection; a practice involving exposure to radiation should produce sufficient benefit to the exposed individual or to society to offset the radiation detriment it causes. ▪ To limit tissue reactions, the dose limit to the lens of the eye is 50 mGy per year, and the dose limit to localized areas of the skin, hands, and feet is 500 mSv per year. ▪ Once a pregnancy is declared, the NCRP recommends a monthly limit 0.5 mSv to the embryo or fetus. ▪ The effective dose in a year should not exceed 50 mSv (NCRP). ▪ All radiation exposures are governed by the ALARA principle. PLEASE REFER TO THE BOOK CHAPTER 16 FOR MORE INFORMATION ANY QESTTIONS?