Radiation Protection

1. 6 Radiation Protection

2. Objectives • Define the key words. • Adopt the ALARA concept. • Use the selection criteria guidelines to explain the need for prescribed radiographs. • Explain the roles communication, working knowledge of quality radiographs, and education play in preventing unnecessary radiation exposure.

3. Objectives • Explain the roles technique and exposure choices play in preventing unnecessary radiation exposure. • Explain the function of the filter. • State the filtration requirements for an intraoral dental x-ray unit that operates above and below 70 kVp.

4. Objectives • Compare inherent, added, and total filtration. • State the federally mandated diameter of the intraoral dental x-ray beam at the patient’s skin. • Explain the difference between round and rectangular collimation. • List the two functions of a collimator.

5. Objectives • Explain how PID shape and length contribute to reducing patient radiation exposure. • Identify film speeds currently available for dental radiography use. • Explain the role image receptor holders play in reducing patient radiation exposure.

6. Objectives • Advocate the use of the lead/lead equivalent thyroid collar and apron. • Explain the role darkroom protocol and film handling play in reducing patient radiation exposure. • Summarize the radiation protection methods for the patient.

7. Objectives • Explain the roles time, shielding, and distance play in protecting the radiographer from unnecessary radiation exposure. • Utilize distance and location to take a position the appropriate distance and angle from the x-ray source at the patient’s head during an exposure.

8. Objectives • Describe monitoring devices used to detect radiation. • Summarize the radiation protection methods for the radiographer.

9. Objectives • List the organizations responsible for recommending and setting exposure limits. • State the maximum permissible dose (MPD) for radiation workers and for the general public.

10. Key Words • Added filtration • ALARA (as low as reasonably achievable) • Aluminum equivalent • Area monitoring • Collimation

11. Key Words • DIS (direct ion storage) monitor • Dosimeter • Exposure factors • Film badge • Film/image receptor holder • Filter

12. Key Words Filtration Half-value layer Inherent filtration Lead apron Lead equivalent MPD (maximum permissible dose) Monitoring

13. Key Words OSL (optically stimulated luminescence) monitor Personnel monitoring Personnel monitoring device

14. Key Words • PID (position indicating device)/BID (beam indicating device) • Primary beam • Protective barrier • Radiation leakage • Radiation workers

15. Key Words • Retake radiographs • Scatter (secondary) radiation • Selection criteria • Structural shielding • Thermoluminescent dosimeter (TLD) • Thyroid collar • Total filtratio

16. Introduction • Although it is the consensus of radiobiologists that the dose received from a dental x-ray exposure is not likely to be harmful, even the experts do not know what risk a small dose carries.

17. Introduction • The patient has agreed to be subjected to the risks of radiation exposure because he/she believes that the oral health care practitioner will follow safety protocols that protect the patient from excess exposure.

18. Introduction • In this chapter, we discuss radiation safety protocols, including selection criteria used in prescribing dental radiographs and methods to minimize x-ray exposure to both the dental patient and the radiographer.

19. ALARA “As Low As Reasonably Achievable”

20. Protection Measures for the Patient • Professional judgment • Technical ability of the operator • Technique standards • Equipment standards • Optimum film processing

21. Protection Measuresfor the Patient • Professional Judgment • Use evidence-based selection criteria when determining which patients need radiographs. • Guidelines adopted by the American Dental Association that assist in deciding when, what type, and how many radiographs should be taken are shown in Table 6-1.

22. Table 6-1 Guidelines for Prescribing Dental Radiographs

23. Table 6-1 Guidelines for Prescribing Dental Radiographs

24. Table 6-1 Guidelines for Prescribing Dental Radiographs

25. Protection Measuresfor the Patient • Technical Ability of the Operator • Communication — clear instructions; patient cooperation • Working knowledge of quality radiographs — understand what a quality dental radiograph should image • Education — continuing education is important

26. Protection Measuresfor the Patient • Technique Standards • Intraoral technique choice — first choice; The paralleling technique yields more accurate and precisely sized radiographic images • Exposure factors — select the appropriate exposure factors — kilovoltage(kVp), milliamperage (mA), and time.

27. Protection Measuresfor the Patient • Equipment Standards: The Federal Performance Standard for Diagnostic X-ray Equipment, effective August 1974. • Provisions require that all x-ray equipment manufactured after this date meet certain radiation safety requirements including filtration, collimation, and PID

28. Figure 6-1 Collimator and filter. The collimator is a lead washer that restricts the size of the x-ray beam. The filter is an aluminum disc that filters (removes) the long wavelength x-rays.

29. Figure 6-2 Effect of filtration on skin exposure. Aluminum filters selectively absorb the long wavelength x-rays.

30. Figure 6-3 Effect of collimation on primary beam. Lead collimators control the shape and size of the primary beam. The beam is limited to the approximate size of the image receptor.

31. Figure 6-4 External collimator attaches to the PID to reduce the area of radiation exposure.

32. Figure 6-5 The collimator restricts the size of the primary beam to 2.75 in. (7 cm) at the end of the PID.

33. Figure 6-6 Although circular collimation provides a large enough area of exposure to adequately cover a size #2 image receptor, the patient also receives excess radiation not needed for the exposure of this receptor.

34. Figure 6-7 Rectangular PIDs restrict the x-ray beam to the approximate size of a #2 intraoral image receptor. Rectangular PIDs are available in 8, 12, and 16 inches (20.5, 30, and 41 cm). (Courtesy of Margraf Dental Manufacturing Inc.)

35. Figure 6-8 Plastic closed-ended, pointed “cones” are no longer used.

36. Figure 6-9 Round PIDs are available in 16, 12, and 8 inches (41, 30, and 20.5 cm).

37. Figure 6-10 Target-surface distance. The longer the target-surface distance, the more parallel the x-rays and the less tissue exposed. Note that the beam size at the patient’s skin entrance is 2.75 in. (7 cm) for both target-surfacedistances. It is the exit beam size that increases to expose a larger area when using the shorter target-surface distance.

38. Figure 6-11 Many image receptor holding devices are available to fit most situations. The use of a holder prevents asking patients to put their fingers in the path of the primary beam.

39. Figure 6-12 Lead aprons and thyroid collars are available in a wide range of sizes. Aprons are available with an attached thyroid collar, or the thyroid collar may be a separate part.

40. Figure 6-13 Patient protected with lead apron with thyroid collar in place.

41. Protection Measuresfor the Patient • Optimum Film Processing • Processing errors increase patient radiation exposure by resulting in retake radiographs. • Patient protection techniques should be used at all times to keep radiation exposures as low as possible

42. Box 6-1 Summary of Protection Methods for the Patient

43. Protection Methods for the Radiographer • All measures taken to protect the patient from radiation also benefit the radiographer. • Radiation protection methods include time, shielding, and distance. • The radiographer should spend a minimal amount of time, protected by shielding, at the greatest distance from the source of radiation to avoid unnecessary exposure.

44. Box 6-2 Summary of Methods to Protect the Radiographer

45. Figure 6-14 Distance is an effective means of reducing exposure from scatter radiation.

46. Figure 6-15 When structural shielding is not available, the radiographer should stand in a position at least 6 ft(1.83 m) from the head of the patient at an angle of 45º to the exiting primary beam.

47. Radiation Monitoring • Area monitoring • Personnel monitoring: Types • Film badge • Thermoluminescent dosimeter (TLD) • OSL (optimally stimulated luminescence) monitor • DIS (direct ion stimulation) monitor

48. Table 6-2 Types of Personnel Monitoring Devices

49. Figure 6-16 OSL radiation monitor worn bythe radiographer to monitor radiation exposure. (Courtesy of Landauer, Inc.)

50. Figure 6-17 DIS radiation monitor. Sized and shaped similar to a thumb drive, this device has a clip to allow the radiographer to wear the monitor while working with ionizing radiation. The device uses a USB connector to plug into a computer with Internet access. When logged on to the manufacturer’s Web site, real-time radiation exposure readings may be downloaded from the device. (Courtesy of Quantum Products.)