5.radiation protection


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5.radiation protection

  2. 2. Contents • Introduction • Patient protection measures • Operator protection measures • Enviornment protection measures • Radiation exposure guidelines • Radiation protection and patient education • Conclusion • References
  3. 3. Introduction • Many of the early pioneers in dental radiography suffered from the adverse effects of radiation. • Some pioneers lost fingers, limbs, and ultimately their lives to excessive doses of radiation. • Hazards of radiation are well documented, and radiation protection measures can be used to minimize radiation exposure to both the dental patient and the dental radiologist.
  4. 4. • X-radiation causes biologic changes in living cells and adversely affects all living tissue. • Use of proper patient protection techniques, the amount of x- radiation received by a dental patient can be minimized. • Patient protection techniques - Before, During, After x-ray exposure. Patient protection measures
  5. 5. • Before Exposure • Patient protection measures can be used before any x- radiation exposure. • Proper prescribing of dental radiographs and the use of equipment can minimize the amount of x-radiation that a dental patient receives.
  6. 6. • PRESCRIBING DENTAL RADIOGRAPHS • First important step in limiting the amount of x-radiation received by a dental patient - proper prescribing, or ordering, of dental radiographs
  7. 7. • Dentists (should) exercise professional judgment when prescribing diagnostic radiographs for dental patients. • Diagnostic radiography should be used only after clinical examination, consideration of the patient's history and consideration of both the dental and the general health needs of the patient.
  8. 8. • PROPER EQUIPMENT • Another important step in limiting the amount of x- radiation • Dental x-ray tube head must be equipped with appropriate aluminum filters, lead collimator, and position-indicating device.
  9. 9. • FILTRATION Purpose of filtration is to remove low- energy x-ray photons resulting in decreased patient exposure with no loss of radiologic information
  10. 10. Two types of filtration 1.Inherent filtration and 2.Added filtration. • Inherent Filtration : takes place when the primary beam passes through the glass window of the x-ray tube, the insulating oil, and the tube head seal. • Approximately 0.5 to 1.0 millimeter (mm) of aluminum.
  11. 11. • Added Filtration : refers to the placement of aluminum disks in the path of x-ray beam between the collimator and the tube head seal. • Aluminum disks added to the tube head in 0.5-mm increments.
  12. 12. • Total Filtration - Inherent Filtration + Added Filtration • Dental X ray machines - at or below 70 (kVp) require a minimum total of 1.5 mm aluminum filtration. • Above 70 kVp require a minimum total of 2.5 mm aluminum filtration • Filtration of the x-ray beam results in higher energy and more penetrating useful beam. • Disadvantage of using filters - 1. Increase exposure time 2.Decrease in the contrast
  13. 13. • COLLIMATION • Restrict the size and shape of the x-ray beam and reduce patient exposure. • Collimator, or lead plate with a hole in the middle, is fitted directly over the opening of the machine housing where the x- ray beam exits the tube head .
  14. 14. • Collimator may have either a round or rectangular opening . • Rectangular collimator restricts the size of the x ray beam to an area slightly larger than size 2 intraoral film and significantly reduces patient exposure. • Circular collimator produces a cone-shaped beam - 2.75 inches in diameter, considerably larger than a size 2 intraoral film.
  15. 15. • when the x-ray tube is operated above 50kVp - x-ray beam should be collimated so that the field of radiation is"contained in a circle having a diameter of no more than 7 cm (2 3/4 inches)”. • Coliimation decreases Risk of radiation, Minimises scattered radiation and Decreases the fog, with a sharper image and better contrast
  16. 16. • POSITION-INDICATING DEVICE OR CONE • Extension of the x ray tube head used to direct the x-ray beam. • Help to minimize the volume of tissue irradiated • Increase the target film distance by using longer position indicating devices to direct the X ray beam.
  17. 17. • Three basic types of PIDs: (1) Conical, (2) Rectangular, (3) Round. • Conical PID appears as a closed, pointed plastic cone. • x-rays exit from the pointed cone, penetrate the plastic and produce scatter radiation- no longer used in dentistry
  18. 18. • Open-ended and lead-lined rectangular or round PIDs are used -do not produce scatter radiation. • Available in two lengths: short (8 inch) long (16 inch).
  19. 19. • long PID is preferred because less divergence of the x-ray beam occurs . • Rectangular type is most effective in reducing patient exposure.
  20. 20. • During Exposure Thyroid collar, Lead apron, Fast film, Film-holding devices limit the amount of radiation received by the patient. • Exposure factors and good technique - further protect the patient from excess exposure to x-radiation.
  21. 21. • THYROID COLLAR • Flexible lead shield placed securely around the patient's neck to protect thyroid gland - scatter radiation. • Separate shield or part of lead apron - thickness of 0.2 mm.
  22. 22. • Recommended for all intraoral films as thyroid gland is exposed to x-radiation because of its location. • Not recommended with extra oral films - obscures information on the film resulting in non diagnostic radiograph.
  23. 23. • Lead apron • Flexible shield placed over the patient's chest and lap to protect the reproductive and blood-forming tissues from scatter radiation • Recommended for all intraoral and extra oral films with protective equivalent of l/4th mm of lead.
  24. 24. • Act as secondary measure to protect the patient • Should not be substituted for use of fast films, lead collimation and aluminum filtration which are primary means of reducing exposure to the patient.
  25. 25. If holding a patient is required… • Use shielding Apron, gloves, thyroid shield, glasses • Avoid exposing assisting person to the primary beam.
  26. 26. • Gloves, aprons ,eyewear Protect from scatter or transmitted radiation, • Eye Protection Glasses 0.75mm Pb (0.9% @ 90kV)
  27. 27. • Hand protection • Gloves • 0.5mm Pb (1.2% @ 90kV) • 1.4 kg each • Person assisting the patient must wear a lead apron and lead gloves if their hands will be in the beam.
  28. 28. 03/04/2014 • Solid 2mm Pb 10% @ 90kV • Flexible 0.5mm Pb 2.5% @ 90 kV Gonad protection (patient)
  29. 29. • Fast film • Most effective method of reducing patients exposure to x- radiation. • Avaliable for both intraoral and extra oral radiography. • Intraoral dental x-ray film - available in three speed groups-D, E, and F.
  30. 30. • Clinically, film speed of group E is almost twice as fast (sensitive) as film of group D , about 50 times as fast as regular dental x-ray film. • F-speed film requires about 75% exposure of E-speed film and only about 40% that of D-speed.
  31. 31. • F-speed film has same density range, latitude, contrast, image quality as D- and E-speed films without sacrifice of diagnostic information. • Current digital sensors offer equal or greater dose saving than F speed film and comparable diagnostic utility.
  32. 32. Intensifying screens • Used in extra oral radiography - use the rare earth elements gadolinium and lanthanum. • Emit green light on interaction with x rays. • Decrease patient exposure by about 55% in panoramic and cephalometric radiography compared with older calcium tungstate screens.
  33. 33. • Focal spot film distance • X-rays are less divergent at a longer distace , leading decrease in the volume of the patient exposed . • Use of long source to skin distance of 40 cm, rather than short distance of 20 cm decreases exposure by 10 to 25 %
  34. 34. • Equipment operating below 50 kVp should have a minimum distance af 10 cm (4") from the end of the PID to the focal spot. • Above 50 kVp should have a minimum distance of 18 cm (7”) from the end of the PID to the focal spot.
  35. 35. • Film-holding devices • Helps to stabilize the film position in the mouth and reduces the chances of movement . • Eliminates the need for the patient to hold the film in place.
  36. 36. • Patient's finger is not exposed to unnecessary radiation. • Possibility of misaligning the X- ray tube and partially missing the film (cone cut), is also reduced.
  37. 37. • Exposure factors selection • Dental radiologist can control the exposure factors by adjusting the Kilovoltage peak, Milliamperage, and Time settings on the control panel of the dental x-ray machine. • limiting the amount x ray radiation exposure to patient. • Setting of 70 to 90 kVp keeps patient exposure to a minimum.
  38. 38. • PROPER TECHNIQUE • Ensure diagnostic quality of films and reduces the amount of exposure patient receives. • To produce diagnostic films, radiologist/ radiographer must have thorough knowledge of the techniques most often used in dental radiography.
  39. 39. • AFTER EXPOSURE • After the films have been exposed, they must be handled and processed. • Meticulous film handling and proper film-processing techniques are critical for the production of high-quality diagnostic radiographs
  40. 40. • OPERATOR PROTECTION MEASURES • Dental radiologist must use proper protection measures to avoid occupational exposure to x-radiation (e.g., primary radiation, leakage radiation, scatter radiation). • Minimize the amount of radiation that a dental radiologist receives. • And includes 1. Protection guidelines 2. Radiation-monitoring devices.
  41. 41. • Protection guidelines • Include recommendations on Distance, Position, and Shielding.
  42. 42. • Distance and position - recommendations • If no barrier is available, the operator should stand at least 6 feet from the patient, • At an angle of 90 to 135 degrees to the central ray of the x-ray beam when the exposure is made.
  43. 43. • Proper operator position also includes the following: • Never hold a film in place for a patient during x-ray exposure. • Never hold the tube head during x-ray exposure.
  44. 44. • Shielding recommendations • Dental radiologist should stand behind a protective barrier such as a wall during x-ray exposure • Constructed of gypsum wall board.
  45. 45. • Radiation Monitoring • Used to identify excess occupational exposure and to protect the dental radiologist. • Includes monitoring of both equipment and personnel.
  46. 46. • Equipment monitoring • Dental x-ray machines must be monitored for leakage radiation through the use of a film device. • Obtained through the state health department or from manufacturers of dental x-ray equipment.
  47. 47. • Personnel monitoring • Amount of x-radiation that reaches the body of the dental radiologist can be measured through the use of a personal- monitoring device known as a film badge.
  48. 48. . • Consists of a piece of radiographic film in a plastic holder. • Radiologist - have his or her own film badge • Worn at waist level whenever exposing x-ray films. • Should never be worn when the radiologist is undergoing x-ray exposure. • Film badges not worn, stored in radiation-safe area
  49. 49. • After the dental radiologist has worn the film badge for a specified interval (eg., 1 week, 1 month), the badge is returned to the service company. • Company processes and evaluates the film for exposure • Provides the dental office with an exposure report for each radiologist. • HARING & HOWERTON Dental Radiography 3rd edition
  50. 50. • Advantages • Inexpensive • Easy to handle and process • Reasonably accurate • Disadvantages • Can not be reused • Sensitive to heat and humidity • Must be changed monthly Film Badges
  51. 51. Thermoluminescent dosemeters • Measurement range 0. 1 µSv to 5 Sv
  52. 52. • TLD has several Advantages over film badges. • Not sensitive to heat or humidity • More sensitive and accurate. • Can be changed quarterly instead of monthly • Disadvantages • Cost but changing badges less frequently than monthly eliminates cost problem.
  53. 53. • ENVIORNMENT PROTECTION MEASURES • Surrounding environment must be protected from radiation to avoid exposure to persons in the environment • Primary beam - never be directed at any one other than patient. • Patient should be positioned such that the X-ray beam aimed at the wall of the room and not through the door or other opening where people may be located,
  54. 54. • Walls made of 3" of concrete, or 1 mm of lead will suffice to protect adjacent rooms, even if the work load in the radiology department is high. • An alternative to lead is Barium due to it's High atomic number, High density and High linear coefficient of attenuation. • Used in the form of Barium Plaster or Barium Concrete.
  55. 55. • If it is not possible to incorporate lead or barium into the walls, they can be lined with lead plywood, 0.25 mm of lead sandwiched between layers of wood.
  56. 56. • Primary barrier should be incorporated in any part of the floor or ceiling of the room at which the beam is fired. • Secondary barrier in the walls, provide protection against scattered or leakage radiation and as exposure rates are small they are 1/2 the thickness of the primary wall.
  57. 57. • Windows: • As the patient is being irradiated, window is provided so that the operator can see. • Situated, where the primary beam is not directed on it • Lead glass should be used
  58. 58. • Doors - radiology room should function as secondary barriers having lead incorporated in them. • Switches may be incorporated so that the beam is cut off as soon as the door is opened and not allow the beam to be switched on till the door is closed completely.
  59. 59. • Warning Light and Placard • Warning signal (red light ) should be placed at an conspicuous place outside the X-ray room which should go on when the exposure button is pressed, or • Placard should be placed to signal that the process of X-ray taking is in progress.
  60. 60. • Quality assurance • Defined as any planned activity to ensure that a dental office will consistently produce high quality images with minimum exposure to patients and personnel.
  61. 61. • Regular radiation surveys • Should be performed at regular intervals as the amount of exposure is dependent on many factors, such as : • Machine's kilo voltage • Work load of the X-ray machine • X-ray absorbing ability of the walls • Amount of time the adjacent areas are occupied by people.
  62. 62. • RADIATION EXPOSURE GUIDELINES • Protect the patient and operator from excess radiation exposure, • Guidelines include 1.Radiation safety legislation 2.Exposure limits for the general public and for persons who are occupationally exposed to radiation.
  63. 63. • Radiation Safety Legislation • Established at both the state and the federal level to protect the patient, operator, and general public from radiation hazards. • At federal level - Radiation Control for Health and Safety Act was enacted in 1968 to standardize the performance of x-ray equipment .
  64. 64. • Federal Consumer-Patient Radiation Health and Safety Act was enacted in 1981 to address the issues of the education and certification of persons using radiographic equipment. • Radiation legislation varies greatly from state to state. • Dental radiologist must be familiar with the laws that apply to his or her workplace.
  65. 65. • Exposure limits • Maximum Permissible Dose: • Defined by the NCRP as the maximum dose equivalent that a body is permitted to receive in a specific period of time. • MPD - dose of radiation that the body can endure with little or no injury.
  66. 66. • Maximum Accumulated Dose • When occupationally exposed workers must not exceed an accumulated lifetime radiation dose. • Determined by formula based on the worker's age. • N refers to the person's age in years. • 18 refers to the minimum required age of a person who works with radiation.)
  67. 67. • ALAR A CONCEPT • states that all exposure to radiation must be kept to a minimum, or "as low as reasonably achievable.'' • To provide protection for both patients and operator. • Every possible method of reducing exposure to radiation should be employed to minimize risk.
  68. 68. • RADIATION PROTECTION AND PATIENT EDUCATION • Education and orientation of all radiation personnel to the ill effects of radiation is mandatory. • Continuing education programs keep them alert to the possible risk and orient them to new equipment.
  69. 69. • Dental radiologist must be prepared to explain exactly how patients are protected before, during, and after x-ray exposure • Printed handouts or pamphlets outlining the steps used to protect patients from excess radiation can be provided to the patient. • Placed in reception area or room where dental radiographs are taken.
  70. 70. • Recommendations of NCRP • Dentists Role in Radiation Protection • Establish a radiation protection program • Prescribe all radiographic examinations • Shall conduct a clinical history and physical exam and determine health benefit to patient from the radiographic procedure • Shall obtain guidance from a qualified expert - facility design & radiation protection
  71. 71. • Dentists Role in Patient Protection • Shall make an effort to obtain recent radiographs from patient's previous dentist • Take radiographs only if indicated after an evaluation of clinical history, physical exam or laboratory findings • Shall limit radiographic examinations of symptomatic patients to those required for diagnosis and treatment of current disease • Shall not expose radiographs for administrative purposes
  72. 72. Conclusion Basi
  73. 73. References • Oral radiology Principles and Interpretation, White and Pharoah – Fifth edition • Textbook of Dental and maxillofacial Radiology, Freny. R. Karjodkar – 2 edition • Essentials of Dental Radiography and Radiology, Eric Whaites – Fourth edition
  74. 74. • J. Anthony Seibert, “X-Ray Imaging Physics for Nuclear Medicine Technologists. Part 1: Basic Principles of X-Ray Production” J Nucl Med Technol 2004; 32:139–147