radiation protection and safetya-141003084618-phpapp02.pptx

Radiation prottection and Measurement

1. Radiation detection and measurement

2. The instruments used to detect radiation are referred to as radiation detection devices . Instruments used to measure radiation are called radiation dosimeters

3. Devices monitor and record ionizing radiation doses (occupational exposure) Must distinguish from background radiation DOSIMETRY

4. Personnel Dosimetry Personnel dosimetry refers to the monitoring of individuals who are exposed to radiation during the course of their work. Personnel dosimetry policies need to be in place for all occupationally exposed individuals. The data from the dosimeter are reliable only when the dosimeters are properly worn, receive proper care, and are returned on time.

5. The radiation measurement is a time-integrated dose , i.e., the dose summed over a period of time, usually about 3 months. The dose is subsequently stated as an estimate of the effective dose equivalent to the whole body in mSv for the reporting period. Dosimeters used for personnel monitoring have dose measurement limit of 0.1 - 0.2 mSv

6. Proper care includes not irradiating the dosimeter except during occupational exposure and ensuring proper environmental conditions Monitoring is accomplished through the use of personnel dosimeters such as the pocket dosimeter, the film badge the thermoluminescent dosimeter

7. Pocket Dosimeter Outwardly resembles a fountain pen . It consists of a thimble ionization chamber with an eyepiece and a transparent scale, a hollow charging rod a fixed and a movable fiber. electrometer----separate -----built-in (self reading type)

8. The ability of radiation to produce ionization in air is the basis for radiation detection by the ionization chamber. It consists of an electrode positioned in the middle of a cylinder that contains gas. When x-rays enter the chamber, they ionize the gas to form negative ions (electrons) and positive ions (positrons).

9. The electrons are collected by the positively charged rod, while the positive ions are attracted to the negatively charged wall of the cylinder. The resulting small current from the chamber is subsequently amplified and measured. The strength of the current is proportional to the radiation intensity.

10. Is sensitive for exposures upto 0.2 R Disadvantages ------ Easily damaged Unreliable in inexperienced hands Does not provide a permanent record

11. Film Badge Monitoring These badges use small x-ray films sandwiched between several filters to help detect radiation. The photographic effect, which refers to the ability of radiation to blacken photographic films, is the basis of detectors that use film.

12. Film badge detects beta, gamma, X Ray

13. Wearing the badge - wear the badge on the collar region, because the collar region including head, neck, and lens of the eyes are unprotected . Wearing period- Each member of staff wears film badge for a period of 4 weeks. At the end of period the film inside is changed. The exposed film is sent to BARC. Useful for detecting radiation at or above 0.1 msv (10 mrem )

14. Advantages inexpensive, easy to use, permanent record of exposure, wide range of sensitivity ( 0.2 – 2000 msv ), identifies type and energy of exposure,

15. disadvantages they are not sensitive enough to capture very low levels of radiation( < 0.15 msv ), Their susceptibility to fogging caused by high temperatures , humidity and light means that they cannot and should not be worn for longer than a 4-week period at a stretch, Enormous task to chemically process a large number of small films and subsequently compare each to some standard test film.

16. Thermo luminescent dosimetry (TLD) Monitoring The limitations of the film badge are overcome by the thermo luminescent dosimeter (TLD). Thermo luminescence is the property of certain materials to emit light when they are stimulated by heat. Materials such as lithium fluoride ( LiF ), lithium borate (Li2B4O7), calcium fluoride (CaF2), and calcium sulfate (CaSO4) have been used to make TLDs

17. When an LiF crystal is exposed to radiation, a few electrons become trapped in higher energy levels. For these electrons to return to their normal energy levels, the LiF crystal must be heated. As the electrons return to their stable state, light is emitted because of the energy difference between two orbital levels. The amount of light emitted is measured (by a photomultiplier tube) and it is proportional to the radiation dose.

18. The measurement of radiation from a TLD is a two-step procedure. In step 1, the TLD is exposed to the radiation. In step 2, the LiF crystal is placed in a TLD analyzer, where it is exposed to heat.

19. As the crystal is exposed to increasing temperatures, light is emitted. When the intensity of light is plotted as a function of the temperature, a glow curve results. The glow curve can be used to find out how much radiation energy is received by the crystal because the highest peak and the area under the curve are proportional to the energy of the radiation.

20. Advantages The TLD can measure exposures to individuals as low as 5 mR can withstand a certain degree of heat, humidity, and pressure Their crystals are reusable Is very compact ( suitable even for finger dosimetry) And instantaneous readings are possible if the department has a TLD analyzer. Response to radiation is proportional upto 400 R Disadvantages Very expensive No permanent record ( other than glow curves) Cannot distinguish radioactive contamination. The greatest disadvantage of a TLD is its cost

21. Storing TLD Badges Badge must not be left in an area where it could receive a radiation exposure when not worn by the individual (e.g. On a lab coat or left near a radiation source) Store badges in a dark area with low radiation background (in low light away from fluorescent or uv lights, heat and sunlight) Lost or damaged badges should be reported immediately to the radiation safety officer and a replacement badge will be issued

22. The Regulatory Bodies

23. There are various Regulatory Bodies at the international and National level, which lay down norms for radiation protection. These are the International Commission for Radiation Protection ( ICRP), the National Commission for Radiation Protection (NCRP ) in America, and the Atomic Energy Regulatory Board (AERB) in India.

24. The International Commission of Radiation Protection (ICRP) was formed in 1928 on the recommendation of the first International Congress of Radiology in 1925. The commission consists of 12 members and a chairman and a secretary who are chosen from across the world based on their expertise. The first International Congress also initiated the birth of the ICRU or the International Commission on Radiation Units and measurements

25. The Indian regulatory board is the AERB, Atomic Energy Regulatory Board. The Atomic Energy Regulatory Board was constituted on November 15, 1983 by the President of India by exercising the powers conferred by Section 27 of the Atomic Energy Act, 1962 to carry out certain regulatory and safety functions under the Act.

26. Radiation safety in handling of radiation generating equipment is governed by section 17 of the Atomic Energy Act , 1962, and the Radiation Protection Rules (RPR) The “ Radiation Surveillance Procedures of Medical Applications of Radiation, ” specify general requirements for ensuring radiation protection in installation and handling of X-ray equipment. Guidance and practical aspects on implementing the requirements of this Code are provided in revised documents issued by AERB in the year 2001

27. Dose Limits Recommended by ICRP (1991) Exposure Dose Limit (mSv per year) Condition Occupational Apprentices Public (16-18 years) Whole body : 20 mSv per year, 6 mSv in a year 1 mSv in a year, (effective dose) averaged over defined averaged over period of 5 years with 5 years, no more than 50 mSv in a single year Parts of the body : (equivalent dose) Lens of the eye 150 mSv per year 50 mSv in a year 15 mSv in a year Skin* 500 mSv per year 150mSv in a year 50 mSv in a year Hands and feet** 500 mSv per year 150 mSv in a year 50 mSv in a year *Averaged over areas of no more than any 1 cm 2 regardless of the area exposed. The nominal depth is 7.0 mg cm -2 **Averaged over areas of the skin not exceeding about 100 cm 2 Note 1.Dose limit for Women upon declaration of pregnancy - 2 mSv measured on the surface of the abdomen and 1/20 th of ALI for exposure to internal emitters. Note 2.Dose limits do not apply to medical exposures, to natural sources of radiation and under conditions resulting from accidents.

28. Radiation protection survey and programme

29. The responsibility for establishing a radiation protection programme rests with the hospital administration / owners of the X-ray facility The administration is expected to appoint a Radiation Safety Committee (RSC), and a Radiation Safety Officer (RSO). It is recommended by NCRP that the RSC should comprise of a radiologist, a medical physicist,, a senior nurse and an internist. It is the duty of RSC to perform a regular radiation protection survey

30. This survey has 5 phases which are: Investigation: To obtain information regarding layout of the department, workload, personnel monitoring and records. Inspection: Each diagnostic installation in the department is examined for its protection status with respect to its operating factors, control booth and availability of protection devices. Measurement: Measurements are conducted on exposure factors. In addition scattered radiation and patient dose measurements in radiography and fluoroscopy are performed.

31. 4. Evaluation: The radiation protection status of the department is evaluated by examination of records, equipment working, status of protective clothing and the radiation doses obtained from phase-3. 5. Recommendations: A report is prepared on the protection status of the department and the problem areas if any identified, for which recommendations are made regarding corrective measures

32. Thin-window GM (Geiger-Mueller) survey meter may be used to - Check leaking radiation Indicate x-ray production Monitor routine operation Ion chamber is used to determine dose rate at the x-ray field. Survey Area Survey meters are calibrated annually .

33. Depicts the organizational flow chart and the administrative and functional components of radiation protection program.

34. CONCLUSION Protect patient, public and staff Remember dose is cumulative Benefit/risk ratio Principles of radiation protection Dose reduction = time, distance, shielding High speed film Lead coats to reduced exp. time steps away stop scatter radiation

35. Thanks!!!