Stacy Kopso, M.Ed., RT (R)(M) Radiation Protection Stacy Kopso, M.Ed., RT (R)(M)

Film Badges Thermoluminescent Dosimeters Optically Stimulated Luminescence Dosimeters Pocket Dosimeters Dosimetry reports Radiation Survey Instruments Dose limits Principles of personnel exposure reduction Construction shielding Protective garments

Monitoring of personnel

Monitoring of Personnel Late effect of radiation Exposure to intermittent low doses of radiation over a long period of time Cancer and genetic effects Effective dose limits have been implemented to lessen the possibility of the occurrence of early and late effects of radiation

Monitoring of Personnel Monitoring is mandatory when personnel are likely to receive 25% of the annual effective dose-equivalent limit Dosimetry- measurement of ionizing radiation doses to personnel. Record external doses. Not a protection device! Film badges Thermoluminescent dosimeters (TLD) Optically stimulated luminescence dosimeter (OSL) Pocket dosimeters Normally monitored monthly Records monthly, quarterly, yearly and lifetime exposure Worn outside lead apron at collar level (different locations for specific badges) Pregnant woman 2 badges Collar outside apron Waist under apron

Monitoring of Personnel Film Badges Special radiation-dosimetry film (similar to dental) contained in a light proof package Film is enclosed in a plastic holder Metal filters shield certain parts of the film that permit estimates of dosage and radiation energy Shallow and deep doses can be calculated according to the amount of darkening of the film after processing Worn outside apron at collar level Worn monthly

Monitoring of Personnel Worn at collar level outside of lead apron Control badge kept in a radiation free area Serves as a baseline when compared with the rest of the film badges Can only be worn during work hours Kept away from sources of radiation and excessive heat and high humidity

Film Badge Advantages Disadvantages Simple to use Not reusable Inexpensive Low limit of sensitivity (10mrem) Readily processed by laboratories Accuracy limited to (+ or – )10-20% Provide a permanent record Susceptible to heat, humidity and light leaks

Monitoring of Personnel Thermoluminescent Dosimeters Contain lithium fluoride or calcium fluoride crystals When exposed to ionizing radiation these crystals store radiant energy when heated As they are heated the crystals release energy as light This is measured by a machine that documents the radiation exposure based on how much light is emitted There is a direct relationship between the intensity of light emitted and the radiation dose received by the crystals Commonly worn as finger rings by nuclear medicine personnel (handle radioisotopes)

Thermoluminescent Dosimeter Advantages Disadvantages Can be made very small No permanent record (no archive) Durable Expensive Low exposure limit (5mrem) Accuracy +/- 5% Less sensitive to heat Can be worn for three months Are reusable

TLD

Monitoring of Personnel Optically Stimulated Luminescence Dosimeter (OSL) Contains filters composed of aluminum, tin and copper Houses a thin strip of aluminum oxide The strip is stimulated by using a laser light and becomes luminescent in relation to the amount of radiation it has received Capable of measuring different energy ranges determined by the amount of luminescence detected in the areas underneath the filters These various ranges of energy correspond to deep, eye, and shallow doses

Optically Stimulated Luminescence Dosimeter Advantages Disadvantages Measurement range from 1 mrem to 1,000 mrem (most sensitive reader) More expensive than film or TLD Accuracy +/- 15% Precision within +/- 1 mrem Energy range 5keV to 40MeV Complete re-analysis if necessary Bimonthly readout offered Tamper proof badge Not affected by heat or humidity Whole body, collar, waist (fetal), wrist Measures exposure to x-rays, gamma rays and beta particles

Monitoring of Personnel Pocket Dosimeter Sensitive Instantaneous reading Must be recalibrated daily Only for exposures up to 200mR Ionization chamber inside Review the dosage by viewing a scale through an eyepiece located on the end of the dosimeter

Pocket Dosimeter Advantages Disadvantages Provides an immediate exposure reading No permanent record Measures up to 200mR Not damage proof

Pocket Dosimeter

Monitoring of Personnel Dosimetry report Measured in mrem “M” minimal exposure (1mrem) Must transfer the cumulative total exposures and the remaining dose to new employer

Radiation safety officer (RSO) Determines if an employee has received an overexposure based on the report, the employee is counseled by the RSO Medical physicist, health physicist, radiologist or any other qualified person

Radiation survey instruments

Radiation survey instruments Used to detect and measure radiation Geiger-Muller detector Detects alpha and beta radiation Inert gas-filled tube that briefly conducts electricity when a particle or photon of radiation temporarily makes the gas conductive Tube puts out a pulse which is displayed by a needle, lamp or audible clicks

Geiger-Muller Detector

Radiation survey instruments Gas ionization chamber (cutie pie) Measures x-ray, gamma, alpha and beta Used for measuring dose rates Shielding effectiveness Source containers Radiation areas monitoring Checking results following decontamination procedures

Cutie Pie

Dose limiting recommendations

Dose-Limiting Recommendations ALARA As low as reasonably Time, Distance, Shield NRC ,State, Joint Commission (JC) Enforces radiation protection guidelines State license(varies per state) Radiation machine registration (yearly) Effective Dose limit/Dose equivalent limit- the lowest dose of radiation that will maintain health with no ill effects

Dose-Limiting Recommendations Diagnostic radiology personnel Annual effective dose limit ____rem 5 ____ mSv 50 _____ mrem 5,000 Negligible individual dose (NID) 1mrem/year Minimal amount which does not need to be reported on the dosimetry report

Dose-Limiting Recommendations Public Annual effective dose limit for infrequent exposure ____rem .5 ____mSv 5 _____mrem 500 Frequent exposure .1 rem (1 mSv)

Dose-Limiting Recommendations Occupational Exposures (NCRP # 116) Dose Limits Whole-body 5 rem (50mSv) Lens of eye 15 rem (150mSv) Skin/Extremities 50 rem (500 mSv) Whole body cumulative (lifetime) 30 yr old- 30rems Age x 1 rem (age x 10mSv) Fetus full gestation .5 rem (5mSv) Fetus per month .05 rem (.5 mSv)

Deep Dose Equivalent (DDE) Shallow Dose Equivalent (SDE) External whole body exposure Shallow Dose Equivalent (SDE) External exposure of the skin or extremity Eye Dose Equivalent (EDE) external exposure of the lens of the eye

mAs and Intensity Doubling the mAs, doubles the skin exposure, as long as other factors are held constant (factor of 2) If an original intensity was 200 mR and the mAs value is increased from 10 to 20 mAs, what is the new intensity? 400 mR (increase by a factor of 2) Directly proportional If an original intensity was 200 mR and the maS value is decreased from 100 mAs to 50 mAs, what is the new intensity? 100 mR (decrease in ½)

kVp and Intensity Changing kVp affects radiation intensity by the square of the ratio If 50 kVp produces an intensity of 200mR, what is the new intensity at 100 kVp? 400 mR (increase by 4x)

Structural shielding construction

Structural Shielding Construction Primary protective barriers Located perpendicular to the line of travel of the primary x-ray beam 1/16 inch of lead (PB) Extends up to 7ft from the floor ( height of the upright bucky)

Structural Shielding Construction Secondary Protective Barriers Located parallel to the line of travel of the primary x-ray beam Cover areas exposed only to scatter and leakage radiation 1/32 inch lead (Pb) ½ overlap on primary barrier Plaster or concrete often serves as a secondary barrier without adding lead

Structural Shielding Construction Control booths Secondary protective barrier Window 1.5mm lead (Pb) 7 feet high

Structural Shielding Construction X-ray tube Lead lined metal covering 1.5mm (1/16 inch) Pb Reduces leakage radiation to not exceed 100mR/hr at 3 feet (1 meter)

Structural Shielding Construction Factors that determine protective barrier thickness include distance, time of occupancy, workload and use. Time of occupancy Amount of time a hospital area is occupied by people Controlled area Area occupied by radiation personnel (factor of 1) Reduce the exposure rate to ˂100 mR/week Uncontrolled area Area occupied by non-radiation personnel (public) Reduce exposure to ˂10mR/week Hallways= factor of ¼ Stairways and elevators= factor of 1/16

Structural Shielding Construction Workload Weekly average tube current and tube operating time Measured in milliampere-minutes/week Use factor Percentage of time that the x-ray beam is energized and directed toward a particular wall Primary & secondary wall barriers/use factor of 1 Not a primary/ use factor of ¼

Protective Garments

Protective Garments Lead apron High atomic number Evaluated by half-value layers (HVLs) The lead thickness that will reduce the intensity of radiation to 50% Worn during fluoro work, portables, holding a patient Lead thickness of .25 .5 1mm Pb X-ray attenuation at 75 kVp for 1mm Pb is 99% Maternity apron .5mm Pb + 1mm Pb around abdomen area

Lead Apron

Minimum lead equivalent NCRP #102 .25 mm Pb .5 mm Pb Gloves Apron Bucky slot cover Thyroid Curtain Overhead barrier .35 mm Pb Glasses

Exam considerations

Exam Considerations Mobile exam Proper communication Clear room Shield other patients and pt Radiographer should position himself at right angles to the patient Go around a corner if possible Exposure switch 6 feet

Exam Considerations Fluoroscopic Exam Wrap around apron Lead gloves Bucky slot cover Lead drape

Exam Considerations Fluoroscopic exposure switch Foot pedal or hand switch Deadman (requires constant pressure) Cumulative timing device Produces an audible signal when 5 minutes of fluoro time has been used. Must be reset. Intermittent/Pulsed fluoroscopy Reduces patient exposure X-ray intensity ≤10 R/min HLCF ≤5 R/min

Exam Considerations Source to tabletop distance ˃12inches (30cm) for mobile fluoro ˃15 inches (38cm) for fixed fluoro Total Filtration 2.5mm Al Image intensifier 2mm Pb

Inverse Square Law The intensity of radiation at a given distance from a point source is inversely proportional to the square of the distance of the object from the source When the distance from the x-ray target is doubled, the intensity is ¼ as much as the original exposure Formula I1 = d22 I2 d12

Inverse Square Law

Inverse Square Law If a radiographer stands 2feet from an xray tube and receives an exposure of 1 mR/hr, what will the exposure be if the radiographer stands 4 feet from the xray tube? ¼ 6 feet to 3 feet??? 4 mR