Radiation Protection Chapter 6 PDF

Radiation Protection CHAPTER 6 1 Key Terms Filtration Added filtration Inherent filtration Total filtration ALARA (as low as reasonably achievable) Collimation Dosimeter Half-value layer (HVL) Maximum permissible dose (MPD) Retake radi...

Radiation Protection CHAPTER 6 1 Key Terms Filtration Added filtration Inherent filtration Total filtration ALARA (as low as reasonably achievable) Collimation Dosimeter Half-value layer (HVL) Maximum permissible dose (MPD) Retake radiograph Selection criteria 2 Objectives 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. Explain the roles technique and exposure choices play in preventing unnecessary radiation exposure. Compare inherent, added, and total filtration. State the federally mandated limited diameter of the intraoral dental x-ray. List two functions of a collimator. Explain how PID shape and length contribute to reducing patient radiation exposure. 3 Objectives Summarize radiation protection methods for a patient. Explain the roles time, shielding, and distance play in protecting the radiographer from unnecessary radiation exposure. Utilize distance and location to take a position an appropriate distance and angle from the x-ray source during an exposure. Describe radiation safety protocol for use with portable, handheld x-ray devices. Describe radiation monitoring devices. Summarize radiation protection methods for a radiographer. State the maximum permissible dose (MPD) for radiation workers and for the general public. 4  As Low ALARA As Reasonably Achievable  If no benefit, do NOT expose radiation ALARA Reduce if you can Guidance Culture of professional excellence Protection Measures for the Patient 1. Professional Judgement 2. Operator Ability 3. Technique 4. Equipment 5. Processing 6. Retake policy 7 1. Professional Judgement When to prescribe x-rays –Based on patient needs ◦ Health history ◦ Signs and symptoms ◦ Clinical examination –Ultimately determined by the DDS ADA & UCDH DDS recommendations are found in the clinic manual 8 UCDH Dentist’s Guidelines New and recall patients BWX every 6-12 months FMX or pano once every 3-5 years (choose depending on pt need) EVERY RADIOGRAPH TAKEN MUST BE READ BY A DENTIST 9 10 2. Operator Ability Communicate – The patient must understand what they are to do and why Proper Technique Do it right the first time! CE 11 3. Technique Technique choice What is the best technique for this patient? Paralleling vs. bisecting periapicals (PAs) Exposure Factors 1. kilovoltage (kVp) 2. milliamperage (mA) 3. Time settings 12  4. Equipment: Filtration Filtration Filters out longer wavelength –Long wavelengths have low energy (Long lazy) –Low energy = bad image and radiation –High energy = good image and radiation –Aluminum (usually) –Mandated by federal standards Low-energy High-energy x-rays x-ray 13  4. Equipment: Filtration Half-Value Layer (HVL) Thickness of material it takes to reduce the intensity of the x-ray beam by ½ Usually measured in millimeters of aluminum More accurate than kVp setting 14  4. Equipment: Filtration 1. Inherent ◦ Part of the equipment – not original purpose ◦ It does not meet the standards regulated by state and federal law 2. Added ◦ Placed for filtration purposes ◦ Aluminum disks or samarium ◦ Required by law 1. + 2. = Total Filtration < 70 kVp=1.5 mm aluminum filtration >70 kVp=2.5 mm aluminum filtration 15 4. Equipment: Collimation Scatter radiation is reduced Controls the size and shape of the x-ray beam Round or rectangular Round can be no larger than 2.75 inches The size of the lead collimator opening determines the size of the beam at the end of the PID 16 Figure 6-4 Exposure comparison. (A) Round collimation provides a large area of exposure to adequately cover a size 2 image receptor; patient receives excess radiation not needed for exposure. (B) Rectangular collimation reduces excess exposure to approximate size of the image receptor; precise alignment of the x-ray beam is required to avoid conecut error. Copyright © 2018, 2012, 2007 Pearson Education, Inc. All Rights Reserved 4. Equipment: Position-Indicating Device (PID) May be rectangular or round o Conical is no longer used in dentistry Rectangular and round PID ◦ 8”, 12” or 16” lengths ◦ Open ended and lead lined Longer PID is preferred 18 Figure 6-9 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 inches (7 cm) for both target–surface distances. It is the exit beam size on the other side of the patient’s head that increases to expose a larger area when using the shorter target– surface distance. Copyright © 2018, 2012, 2007 Pearson Education, Inc. All Rights Reserved  4. Equipment: Fast Receptor Speed D=Dexter film Using a faster film requires less radiation A is slowest speed (no longer made) D, E, and F are available F is the fastest speed F=Fast, patient film F-speed film instead of D-speed film reduces patient exposure by 60% !! Digital reduces further 20 4. Equipment: Image receptor holding devices Eliminates the need to hold the receptor with fingers Stabilizes the receptor 21 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. Copyright © 2018, 2012, 2007 Pearson Education, Inc. All Rights Reserved 4. Equipment: Thyroid Collar/Lead Apron The ADA recommends that a lead apron and thyroid collar be used on all patients Exposure from scatter radiation to other parts of the body is minimal Easy to use Patients feel safer No thyroid collar is used for panoramic films Hang or lay flat, NO FOLDING! 23 5. Film Processing Purpose is to eliminate retakes due to processing error Handling ◦ Avoiding artifacts Processing ◦ Time ◦ Temperature ◦ Light 24 5. Retake Policy Keep retakes to a minimum UCDH only 1 retake permitted per image All retakes must be supervised by instructor Exception: May take more than 1 retake with instructor *IF* there is pathology 25 Protection Measures for the Operator 1. Time 2. Shielding 3. Distance 26 1. Operator Protection: Time Time Decrease need for retakes Get in & get out The dental radiographer must avoid the primary beam No holding films 27 2. Operator Protection: Shielding Shielding Recommendations Stand behind a protective barrier Drywall is adequate protection Half value layers are taken into consideration If barriers are not available, follow distance rules 28 3. Operator Protection: Distance Use these rules for when shielding is unavailable Based on Inverse Square Law 6 feet At least 6 feet away from the patient 90 to 45 degree angle As the tube head moves, your safe position moves 29 MAXIMUM SCATTER Copyright © 2018, 2012, 2007 Pearson Education, Inc. All Rights Reserved Handheld X-ray Devices Should only be used when: ◦ Wall-mounted x-ray machine is not available ◦ It isn’t practical to move a patient to an x-ray machine Should be manufactured with increased shielding Hold with both hands Hold in front of the body at mid-torso Patient moves for vertical angulation, not machine 31  Radiation Monitoring Area monitoring ◦Leakage radiation Personnel Monitoring: Dosimeter ◦Radiation monitoring badge ◦Required in some states ◦Worn at waist ◦Does not protect only measures 32 Exposure Limits and Standards 1902 studies began on effects of radiation exposure 1928 organizations formed to protect patients from radiation exposure Today we have governing bodies that regulate the use of radiation State and federal levels 33  Radiation Exposure Guidelines Maximum Permissible Dose (MPD) Amount of radiation the body can endure with the expectation of no injury Not intended for dental radiation exposure Radiation Dose Limits Occupationally exposed persons 50 mSv/year (5.0 rem) Occupationally exposed pregnant and/or under 16 years old 5 mSv/year (0.5 rem) Non-occupationally exposed persons 5 mSv/year (0.5 rem) 34  Radiation Exposure Guidelines Radiation Dose Limits Occupationally exposed persons 50 mSv/year (5.0 rem) Occupationally exposed pregnant women 5 mSv/year (0.5 rem) Non-occupationally exposed persons 5 mSv/year (0.5 rem) Lethal dose 4,000-5,000 mSv Compare to Full mouth series 0.0234 mSv 213 FMX in 1 year = non-occupational MPD 2,137 FMX in 1 year = occupational MPD 170,940 FMX at once = lethal dose @4,000 35