RADIATION MONITORING DEVICES.pptx

radiation monitoring devices

1. RADIATION MONITORING DEVICES

2. CONTENT Introduction Electromagnetic spectrum Radiation effects Principle of radiation protection Dosimetry Radiation monitoring devices

3. INTRODUCTION

4. TYPES OF RADIATION

5. ELECTROMAGNETIC SPECTRUM

6. RADIATION PROTECTION The principle of radiation protection is to do those things that will minimize exposure of patient and dental personnel and still provide benefits for the patient from use of diagnostic radiography.

7. PRINCIPLE OF RADIATION PROTECTION Justification: Any decision that alters the radiation exposure situation should do more good than harm. Optimization of protection: the likelihood of incurring exposures, the number of people exposed, and the magnitude of their individual doses should all be kept as low as reasonably achievable(ALARA), taking into account economic and societal factors Application of dose limits: The total dose to any individual from regulated sources in planned exposure situations other than medical exposure of patients should not exceed the appropriate limits recommended by the Commission. International Commission on Radiological Protection Radiological protection in medicine. ICRP Publication 105.  Ann ICRP.  2007;37:1–63.

8. ALARA OR ALADA

9. DOSIMETRY Dosimetry is the determination of the quantity of radiation exposure or dose. Radiation dosimetry : Deals with the measurement of the absorbed dose or dose rate resulting from the interaction of ionizing radiation with matter and particularly in different tissues of the body.

10. It is the measure of the energy absorbed by any type of ionizing radiation per unit mass of any type of matter. SI unit is the Gray ( Gy ), was introduced which replaced the traditional unit Rad (radiation absorbed dose), where 1 Gy equals 1 joule/kg It is a measure of radiation quantity, the capacity of the radiation to ionize air. The SI unit of exposure in the air is kerma (Kinetic Energy Released in Matter). Kerma –measures the kinetic energy transferred from photons to electrons and is expressed in units of dose gray ( Gy ), where 1 Gy equals 1 joule/kg. Replaced the Roentgen (R), the traditional unit of radiation exposure measured in air

11. EQUIVALENT DOSE Equivalent dose (H): It is used to compare the biologic effects of different types of radiation on a tissue or organ. It is the sum of the products of the absorbed dose (DT) averaged over a tissue or organ and the radiation weighting factor (WR); HT = Σ WR × DT SI Unit is Sievert

12. Effective Dose (E): It is used to estimate the risk in humans. It is the sum of the products of the equivalent dose to each organ or tissue (HT) and the tissue weighing factor (WT) E = ΣΗT × WT The unit of effective dose is Sievert ( Sv ).

13. MAXIMUM PERMISSIBLE DOSE Maximum Permissible Dose (MPD) is equal to 0.05 Sv /year. This is the equivalent that a person or specified parts of the person shall be allowed to receive in a stated period. i . Average weekly exposure for either patient or operator, is 0.001 Sv . ii. A maximum of 13-week exposure is 0.05 Sv . Should an operator receive more than 0.05 Sv in any 13 week period, he should avoid any further X-ray exposure until his total for the year falls below what he would have received at a rate of 0.05 Sv /year. iii. For the general public the maximum permissible dose is limited to 1/10th or 0.005 Sv /year.

14. RADIATION MONITORING DEVICES

15. Ionization chamber Geiger-Muller counter thimble ionization chamber Photomultiplier tube

16. PERSONAL MONITORING DEVICES A dosimeter is a very rugged form of a device called an electrometer Personal Monitoring devices: a. Pocket dosimeter b. Digital electronic dosimeter c. Film badge d. Thermoluminescent dosimeter

17. AIM OF PERSONAL MONITORING Monitor and control the individual dose. Report and investigate over exposure and recommend necessary remedial measure, if needed Maintain life time cumulative dose record

18. IDEAL MONITORING DEVICE

19. FILM BADGE Used to measure the individual dose from X rays Beta particle Gamma radiation Thermal neutrons Ernest O wollan

20. CONSTRUCTION

21. FILM BADGE The housing of dosimeter is of plastic or metal. 50 mm square (2 in.) by 12 mm (0.5 in.) thick and equipped with a clip for attaching to clothing. It contains one or more film packets, usually standard dental X-ray film packets. Filters modify the response of different areas of the film and thereby provide more information to correct the response to approximate that of tissue. The phenomenon that X-rays blacken photographic films is applied here

22. PHOTOGRAPHY FILM Photographic film is transparent plastic film base coated one/both side with a gelatin emulsion containing small light sensitive silver halide crystals Film is 4x 3 cm wrapped inside by a light tight polythene paper cover There are two films in the badge one is slow and another is fast Supply of film is for a period of one calendar month

23. First window Without any filter It detects alpha particles Due to minimum penetration power of alpha particles no metallic filter is used

24. Second window Filter made of plastic Light white colour It detects beta particles Thickness of filter 1mm

25. Third window & fourth window Filter is made of cadmium Yellow in colour It detects thermal neutrons Thickness of filter: 1 mm Filter is made of thin copper Green in colour It detects low energy X rays Thickness of filter 0.15mm

26. Fifth & sixth window Fifth window Filter is made of thick copper Pink in colour Detects high energy X-rays Thickness of filter: 1mm SIXTH window Filter is made of Lead Black in colour It detects gamma rays Thickness of filter: 1mm

27. WORKING

28. ADVANTAGE DISADVANTAGE Accuracy is only 10 to 50%, as many low energy photons may not penetrate the film. Range of exposure is less. No immediate indication of exposure- all information is retrospective. The badge is usually monitored every 2 weeks, or sometimes in 4 weeks, in cases where it is certain that the radiation hazard is very small. Badges are normally worn at the chest or waist level on the outside of the normal working clothes, to give an indication of the whole body exposure to which the work is subjected Good for measuring any type and energy of radiation. For example, X-rays, gamma radiations. Continuous assessment is possible. Accumulated dose can be calculated. Provides a permanent record of dose received. Simple, robust and relatively inexpensive.

29. DOSIMETER This is used for measurements of the actual dose received by the operator /patient as a result of radiography or radiotherapy exposures and are the most common type of personnel monitoring devices used. Size is small and it also causes nearly the same attenuation of the X-ray beam as does soft tissue, the TLD can very easily be placed on the skin or in the body cavity during exposure. Range 0.2mSv to 10Sv TLD badge can cover a wide range of dose from 10mR to 10000R with the accuracy of 10% THERMOLUMINISCENT

30. TLD badge in India, consists of a TLD card holder cassette of high impact plastic. The TLD card consists of a Nickel plated aluminum plate having 3 symmetrical holes, each of diameter 12 mm, over which 3 identical CaSO4 embedded Teflon disks are dipped (13.2 mm diameter, 0.8 mm thickness, 280 mg weight).

31. PRINCIPLE OF TLD BADGE

32. TLD reader The equipment used to heat the exposed material and measure the emitted light is called the TLD reader. The reading given by this equipment is used as a measure of the absorbed dose to which the material was subjected. The reader comprises of 3 main parts: 1. Heater. 2. Photomultiplier tube. 3. Electronic system

33. Application

34. OPTICALLY STIMULATED LUMINESCENCE DOSIMETER New technology that uses a LASER to trap energy from radiation fields in a tiny crystal Stored energy from the radiation released from dosimeter material by optical stimulation Energy release in form of luminescence. It is more sensitive than TLD Capable to detecting dose as low as 10 microSv Working mechanism similar to TLD except the light emission is stimulated by LASER light Crystalline Aluminium oxide activated with carbon is commonly used.

35. OSL reading process

36. Advantage Disadvantage

37. RPL Glass DOSIMETER

38. POCKET DOSIMETER Pocket dosimeters are used to provide the wearer with an immediate reading of his or her exposure to X-rays and gamma rays. As the name implies, they are commonly worn in the pocket

39. WORKING It has two electrodes which are charged through an external connection. Since they are the same charge, they repel each other. As ionizing radiation passes between the electrodes and the electrically conductive case, the charge on the electrodes is neutralized. When the charge reduces, an electrode moves away from the zero calibration. The magnifier displays this motion against a scale.

40. Digital electronic dosimeter These dosimeters record dose information and dose rate. These dosimeters most often use Geiger-Müller counters . The output of the radiation detector is collected and, when a predetermined exposure has been reached, the collected charge is discharged to trigger an electronic counter. The counter then displays the accumulated exposure and dose rate in digital form.

41. Digital electronic dosimeter Some Digital Electronic Dosimeters include an audible alarm feature that emits an audible signal or chirp with each recorded increment of exposure. Some models can also be set to provide a continuous audible signal when a preset exposure has been reached. This format helps to minimize the reading errors associated with direct reading pocket ionization chamber dosimeters and allows the instrument to achieve a higher maximum readout before resetting is necessary

42. Digital electronic dosimeter The electronic dosimeter is five to two hundred times more sensitive than a TLD. Arrow-Tech dosimeters are rugged, precision instruments about the size of a pocket fountain pen, which are used to measure accumulative doses or quantities of gamma and X-ray radiation. A metal clip is used to attach the dosimeter to an individual's pocket or to any available object in an area to be monitored for total radiation exposure. It is pocket-size, conductive-fiber electroscope with an ion chamber for detecting and indication integrated exposure to gamma and X-radiation. It has a thin wall which permits the penetration and detection of radiation.

43. REFERENCES Eric whites, Essentials of Dental Radiography and Radiology,5 th edition;-57 pg Freny Karjodhkar , Essentials of oral and maxillofacial radiology, 2 nd edition; 75-79. Allan B. Reskin. Advances in Oral Radiology. PSG Publishing Co. 1980. Barr JH, Stephens RG. Radiological Health. In Dental radiology. Pertinent Basic Concepts and their Applications in Clinical Practise. Philadelphia, WB Saunders 1980;66- 80. Baumann M, Saunders M, Joiner MC. Modified Fractionation in Basic Clinical Radiobiology. Ed. Steel GG 2002;147. Bushong SC. Radiologic Science for Technologist, Physics, Biology and Protection, 7th ed, St. Louis, Mosby 2001. Dowd SB, Tilson ER. Practical Radiation Protection and Applied Radiology, 2nd ed, Philadelphia, WB Saunder 1999. Frommer HH. Biological effects of radiation, In Radiology for dental auxiliaries, 6th edition St. Louis, Mosby- year book, 1996;49-67.