RADIATION MONITORING DEVICES R A D I A T I O N P R O T E C T I O N & B I O L O G Y - R H O D E S

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1 RADIATION MONITORING DEVICES R A D I A T I O N P R O T E C T I O N & B I O L O G Y - R H O D E S

2 DETECTION AND MEASUREMENT OF IONIZING RADIATION Dosimeter Dose-measuring device Two classifications: Field survey instruments Personnel monitoring devices

3 PERSONNEL MONITORING Provided to workers who accumulate 1/10 of recommended dose limit Monitoring devices should be worn: Typically between chest and waist If wearing lead apron, at level of collar

4 PLACEMENT OF PERSONNEL DOSIMETER During routine radiographic procedures When a protective apron is not being worn Primary personnel dosimeter should be attached to the clothing on the front of the body at collar level When a protective apron is used Dosimeter should be worn outside the apron at collar level on the anterior surface of the body

5 PLACEMENT OF SECOND MONITOR When a protective apron is worn The first, or primary, dosimeter is to be worn outside the protective apparel at collar level The second dosimeter should be worn beneath a wraparound-style lead apron at waist level Appropriate for departments that utilize two badges or for pregnant radiographers.

6 EXTREMITY DOSIMETER TLD ring badge is worn as a second monitor when performing radiographic procedures that require the hands to be near the primary beam

7 RECORD OF RADIATION EXPOSURE Should be part of the employment record of all radiation workers Values represent the average annual EfD to the whole body

8 BADGE REPORTS State & Federal Guidelines for monitoring Deep Dose, Eye Dose and Shallow Dose Equivalent Doses Doses for the monitor period and cumulative dose M readings are Minimal or below what the monitor can read

9 CONTROL BADGES Provided from manufacturer Stored in rad dept away from exposure Returned with badges Used to identify background exposure that is subtracted from badge readings

10 PERSONNEL DOSIMETERS Characteristics Lightweight, easy to carry Durable material to tolerate normal daily wear Detect and record small & large exposures consistently Not affected by outside influences Inexpensive to purchase and maintain Permit facilities to monitor large numbers of workers in cost-effective manner

11 PERSONNEL MONITORING DEVICES Optically stimulated luminescence (OSL) dosimeter Film badge dosimeter Thermoluminescent dosimeter (TLD) Pocket dosimeter Ion Storage dosimeter

12 OPTICALLY STIMULATED LUMINESCENCE (OSL) DOSIMETER Most common type of personnel monitor Detector: Thin layer of aluminum oxide Laser light processing of aluminum dioxide causes luminescence Level of luminescence proportional to amount of exposure received

13 OSL DOSIMETER Filters of copper, aluminum, plastic, tin and an open window Demonstrate: Energy of exposure If exposure occurred while static or in motion

14 OSL DOSIMETER

15 OSL DOSIMETER Issued on monthly or quarterly basis OK to wear for up to 1 year Sensitive to 1 millirem (mrem) Environmentally stable and durable Landauer site.

16 FIELD OSL DOSIMETERS Designed to monitor badge readings in the field Portable Immediate feedback for emergency situations

17 FILM BADGE DOSIMETER Detector: Two pieces of film in light tight packet Packet placed in holder with filter elements Copper, cadmium, aluminum and open area Filters provide information on energy of radiation

18 FILM BADGE DOSIMETER Film processed and optical density evaluated Demonstrates amount of exposure Sensitive to 10 mrem Environmentally sensitive to: Heat Humidity Pressure Prolonged exposure to light Wear for 1 month

19 THERMOLUMINESCENT DOSIMETER - TLD Detector: Lithium fluoride crystals Crystals store energy when exposed to ionizing radiation Release stored energy as visible light when heated Amount of light released proportional to amount of exposure

20 TLD Sensitivity similar to film badge - 5 mrem Filters include mylar, plastic and copper Environmental sensitivities also similar to film badges Heat, humidity, temperature, pressure, and prolonged exposure to light Compact design Desirable for extremity badges Wear for up to 6 months Data lost after being read

21 . TLD ANALYZER

22 ELECTRONIC PERSONAL DOSIMETER Ionization of air in small chamber Readout occurs digitally Can be read from display on side of dosimeter Range is mr Must be read day of exposure Data lost after reading

23 READING A POCKET ION CHAMBER

24 DIRECT ION STORAGE (DIS ) Reusable Low Cost On-line reading & access Utilized a very sensitive USB memory drive to count ionizations in air. Lowest reading is 3 mr Range 3 mr 500 rem Reusable Can store long and short term doses

25 CARE OF PERSONNEL MONITORING DEVICES Monitors must be worn Monitors must be worn only by individual to which they were assigned Must be turned in for processing when due

26 FIELD SURVEY INSTRUMENTS Must be portable, durable and cleanable Should have immediate readouts Detect radiation and dose/rates Used in Medical facilities or industry

27 RADIATION SURVEY INSTRUMENTS AND AREA MONITORING Gas-filled radiation survey instruments Ionization chamber-type survey meter (cutiepie) Proportional counter Geiger-Müller Detector (GM) detector Other Detectors Scintillation

28 GAS DETECTOR DESIGN

29 VOLTAGE IN ION CHAMBERS R = Region of Recombination I = Ion Chamber P= proportional Region GM = Geiger- Mueller Region CD = Continuous Discharge

30 CUTIE PIE ION CHAMBER Survey Meter X, Gamma & Beta Rate Meter & cumulative Dose 1mr thousands

31 EQUIPMENT TESTING Radiographic and fluoroscopic units can be calibrated with ionization chambers. Must be calibrated periodically to meet state and federal requirements for patient dose evaluation.

32 PROPORTIONAL COUNTERS Not used in X-ray Used to detect Alpha, Beta and lab contamination Detector must be in contact with source to read Alpha (travel short distances)

33 GEIGER-MUELLER SURVEY INSTRUMENTS GM counter for Area monitoring Gas-filled detector Volume of gas between two electrodes Ionizing radiation creates ion pairs in gas Audible sound

34 GM COUNTERS Used to demonstrate presence of radiation Not for precise measurement Most effective with particulate radiation Least effective in detecting x- or gamma radiation

35 SCINTILLATION DETECTION DEVICES Scintillators emit light when stimulated by ionizing radiation Light converted to electric signal Commonly used in nuclear medicine and CT scan equipment Basis for Gamma Camera in nuclear medicine

36 SCINTILLATION DETECTOR