Radiation Protection PDF

Radiation protection by Dr. Noura Ibrahim Protection against radiation: The purpose of the radiation protection standard settings defined by the international commission on radiological protection ( ICRP) 1- Prevent the occurrence of deterministic effects of radiation. 2-limit to an acceptable l...

Radiation protection by Dr. Noura Ibrahim Protection against radiation: The purpose of the radiation protection standard settings defined by the international commission on radiological protection ( ICRP) 1- Prevent the occurrence of deterministic effects of radiation. 2-limit to an acceptable level the occurrence of the stochastic effects of radiation. Adverse health effects of radiation exposure Deterministic effects Stochastic effects Deterministic effects: • Deterministic effects (or nonstochastic health effects) are health effects, that are related directly to the absorbed radiation dose. • the severity of the effect increases as the dose increases. Stochastic effects: • Stochastic effects of ionizing radiation occur by chance, generally occurring without a threshold level of dose. • Probability of occurrence of stochastic effects is proportional to the dose ( increasing chance) but the severity of the effect is independent of the dose received. Principles of radiation protection Justification Optimization Dose limitation Principles of Radiation protection: • Justification: whether benefits of radiation outweigh the risks. • Optimization: if exposure justified then keep it as low as reasonably achievable (ALARA) • Dose limitation: exposure should be within the prescribed dose limits. Dose limitation: The principle of dose limitation means that nobody should be exposed to an unacceptable degree of risk from activities involving radiation exposure. These dose limits are recommended by the International Commission on Radiological Protection (ICRP). In general, these limits are set to limit stochastic effects to an acceptable level, and to prevent deterministic effects completely. The limits are split into two groups, the public, and occupationally exposed workers. According to ICRP, occupational exposure refers to all exposure incurred by workers in the course of their work, except for : 1-any medical exposure 2-the normal local natural background radiation. What are the recommended annual dose limits for radiation exposure? Radiation workers are required to wear thermoluminescent dosimeters so that their exposure can be monitored. Radiation workers who exceed annual limits will be prevented from continuing in their occupations for the rest of the year if they exceed the annual limit Radiation from dental x-rays: Radiation from dental x-ray can’t induce any deterministic effects but may induce stochastic effects. Radiation from dental radiographs is quite minimal and very safe for healthy patients to be exposed to. There are radiation safety considerations In any case to prevent those stochastic effects. once the decision has been made to prescribe x-rays, every reasonable effort must be made to minimize exposure to the patient and dental office personnel. Protection should be for both patients, workers and environment. 1-Considerations to protect the patient: • proper selection of the x-ray machine. • The use of technique factors that result in low patient exposure a)( KPV 60-70) b) DC current c)decreasing time of exposure • The use of fast films . • The use of intensifying screens in extraoral films. • Adherence to correct film processing methods . • The use of digital sensors • The use of rectangular collimators and filtration. • The use of lead aprons and thyroid collars to protect the patient from unnecessary radiation exposure. • Film holders that align the film precisely with the collimated beam are recommended for periapical and bitewing radiographs. • In panoramic x-rays use rare-earth screens for film imaging or use digital systems. • Increase source to skin distance to decrease scattering radiation. 2-Considerations to protect the operator: 1- Xray area should be separated from the outside with lead barrier. 2- operator should stand outside x-ray room during exposure. 3-The operator should stand at least 6 feet (2 m) from the patient, at an angle of 90 to 135 degrees to the central ray of the x-ray beam. 4-The operator should never hold films or sensors in place. 3-Considerations to protect the environment: • Primary beam: should be only directed to the patient not involving any other personnel. • Patient’s position: X-ray beam should be aimed at the wall of the room & not through a door where people may be located. • Shields: walls/floor/roof of the room should be containing lead for protection. Thank you J