Chapter 9 Dose Limits for Exposure to Ionizing Radiation Dose Limits for exposure to Ionizing Radiation apply to: Occupational workers Nonoccupational workers Radiation Dose Specification Equivalent Dose (EqD) quantity that attempts to take into account the variation in biological harm that is produced by different types of radiation. Effective Dose (EfD) A dose that takes into account the dose for all types of ionizing radiation to organs or tissues in the human body. 1 2 Equivalent Dose equation Radiation Weighting Factor W R 3 4 1
Example Effective Dose Equation 5 6 Tissue Weighting Factors W T Advisory and Regulatory Organizations 7 Elsevier items and derived items 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 8 2
Advisory Organizations Advisory Organizations These organizations evaluate the relationship between radiation EqD and biological effects. o International Commission on Radiological Protection (ICRP) o National Council on Radiation Protection (NRCP) o United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) o National Academy of Sciences/National Research Council Committee on Biological Effects of Ionizing Radiation (NAS/NRC-BEIR) 9 10 Why do we have these organizations? United States Regulatory Agencies They make recommendations on what is a safe practice for radiation protection. NOT enforcement (regulatory) agencies! NRC - Nuclear Regulatory Commission (Atomic Energy Commission) Agreement States these states assume the responsibility for enforcing regulations. EPA - Environmental Protection Agency FDA - Food and Drug Administration OSHA Occupational Safety and Health Administration 11 12 3
United States Regulatory Agencies Hospital Oversight Radiation Safety Program Radiation Safety Committee (RSC) Provides guidance and facilitates operations Radiation Safety Officer (RSO) Oversees radiation program daily operations o Medical or Health Physicist o Radiologist o Technologist Usually Nuclear Medicine 13 14 RSO Responsibilities Develops radiation safety program for all persons employed Ensures adequate protection and monitors unsafe practices Monitors and documents exposure Trains personnel regarding safe radiation practices and monitoring Radiation Control for Health & Safety Act of 1968 Protection for the public from unnecessary radiation exposure (from all sources medical, electronic, etc). Went into effect in 1974 Under the direction of the FDA the Center for Devices and Radiologic Health (CDRH) was established (also know as the Bureau of Radiation Health) 15 16 4
Radiation Control for Health & Safety Act of 1968 (cont.) Objectives of the CDRH: o Establish standards for manufacture, installation, assembly, and maintenance for radiation equipment. o Assess biological effects of ionizing radiation, evaluating radiation emissions from electronic products, and conduct research to reduce radiation exposure. ALARA In 1954 the National Committee on Radiation Protection (NCRP) introduced the ALARA concept As Low As Reasonably Achievable Employing proper radiation safety procedures by qualified personnel. the continuation of good radiation protection programs and practices which traditionally have been effective in keeping the average and individual exposures for monitored workers well below the limit 17 18 Consumer-Patient Radiation Health & Safety Act of 1981 Goals for Radiation Protection Standards for accreditation for educational programs and the certification of persons performing radiologic procedures. Established under the direction of the secretary of Health and Human Services NCRP to prevent the occurrence of serious radiationinduced conditions (acute and chronic deterministic effects) in exposed persons and to reduce stochastic effects in exposed persons to a degree that is acceptable in relation to the benefits to the individual and to society from the activities that generate such exposures 19 20 5
Important Points of NCRP Report No. 116 Annual Occupational dose Limit 5 rem (50 msv) Cumulative Effective dose limit (whole body) 1 rem (10mSv) x age Pregnant Radiation worker.5 rem per gestation or.05 rem per month 21 22 Categories for Radiation- Induced Responses Nonstochastic 1. Nonstochastic (deterministic) Effects 2. Stochastic (probabilistic) Effects A nonstochastic or deterministic health effect has a severity that is dependent on dose and is believed to have a threshold level Early nonstochastic (deterministic) somatic effects: These effects occur within minutes, hours, days, or weeks of the time of exposure. Acute Radiation Syndrome (ARS) 23 24 6
Acute Radiation Syndrome (ARS) A collection of symptoms associated with a high-level radiation exposure. Stochastic Stochastic (probabilistic) somatic effects: Late effects of ionizing radiation that are mutational or randomly occurring biological somatic changes, independent of dose. Stochastic is a random process where there is some indeterminacy in its future evolution described by probability distributions. This means that even if the initial condition (or starting point) is known, there are many possibilities the process might go to, but some paths are more probable and others less. http://en.wikipedia.org/wiki/stochastic_process 25 26 Questions? RADT 3403 Radiation Protection Chapter 10 27 7