Radiologic Health & Protection PDF

Radiologic Health & Protection  Terminology. Patient radiation protection. Operator radiation protection. Immediate environment protection. Terminology:  MPD  ALARA MPD: Maximum permissible dose. Is the amount of radiation that an individual...

Radiologic Health & Protection  Terminology. Patient radiation protection. Operator radiation protection. Immediate environment protection. Terminology:  MPD  ALARA MPD: Maximum permissible dose. Is the amount of radiation that an individual is allowed to receive from artificial sources of radiation. e.g. Radiation workers (dentists, assistants) annual MPD 50 msv.  Life time cumulative exposure 10 (times age in year). e.g. public exposure. (annual MPD) 1-5 msv. pregnant women. (Total MPD during gestation period) 5 msv. ALARA: As low as reasonably achievable. Is an important radiation protection concept. Means that every reasonable measure will be taken to assure that occupationally and non-occupationally exposed persons will receive the smallest amount of radiation possible.  Radiation Protection I. Patient radiation II. Operator radiation Immediate environment protection protection radiation protection 1- Position 1- Primary bean 2- Distance 2- Patient position 3- Shielding 3- Shielding 4- Radiation 4- Equipment monitoring 1 2 3 4 5 6 Selection Machine Film Technique Processing Viewing  KVp  Speed  Apron  Ligthing  Viewbox  Current  Screen  Parallel  Method  Filter  Holder  Solutions  Collimotor  Quality  BID  Timer 1- Selection Rules:  Operator should expose no one to x-rays without a good reason.  Routine radiographs should not be taken.  If radiograph would not change the diagnosis a treatment plane, it should not be taken.  Use only the minimum number of films required to adequately treat patient.  e.g. Panoramic rather than full mouth survey. 2- Machine protective measures: a- Kilovoltage (KVP):  The x-ray machine should be operated-at the highest (KVP) consistent with good-image.  Increasing (KVP) from 70-90 KVP Provide :  More (useful) high energy x-ray.  Fewer (useless) low energy x-ray.  23% reduction in effective dose.  Any x-ray machine operated below 60 KVP should not be used. b- Current:  Use constant potential x-ray machine.  i.e. x-ray machine with build-in generator converting alternating current (AC) To direct current (DC): Produce Homogenous beam of:  Consistent wavelength during the whole exposure.  Reduce pt. exposure 20%. c- Filter  X-ray beam should be filtered why?  Filtration removes soft, low-energy, long wavelength ray.  Filtration in intra-oral machine.  Operating at 50-69 should have at 1.5 mm AL equv least filt.  Operating at 70-90 2.5 mm AL equ. Filt.  Filtration in extraoral machine:  Should have both AL & rare-earth filtration.  This combination reduces  pt. exposure 20-80%.  Compared with AL-filtration alone.  No Filter Film Aluminum filter Filtration removes soft, low energy, long wavelength X-rays from the beam d- Collimator  Collimator = restriction of the cross- sectional area of the beam.  Types:  Round collimator.  Rectangular collimator.  Round collimator Rectangular collimator 7 cm in diameter 4  5 cm (almost 3 times the size almost exactly as the size of no. 2 p.A. film of no. 2 p.A. film 4-1 Film 3-2 Film Excess radiation Excess Compared to Advantages Round cell  Reduce patient exposure 55%. radiation  Improve image quality.  Reducing fog from scatter.  Better resolution.  Better contrast. Types of rectangular C Dentsply/Rinn XCP film holder with rectangular BID. with round BID. Mosal precision instruments. e- BID  Used to show operator where the beam will strike the patient. Types Pointed plastic Lead-lined cones Open-ended BID Not recommended 8 inch 12 inch 16 inch short long  Pointed plastic Long – Lead – lined, Cone X , Why? open-ended BID 1- Increase Scattered Is the best, Why? radiation to all areas of 1- Less beam divergence. patient head, neck, 2- Less volume of patient tissue reproductive organs irradiation. 3- Improve diagnostic quality of image. 4- Less scatter radiation. f- Timer Should be electronic not Mechanical  Accurate for exposure. In Accurate when  Less than 1 sec. "dead man used for short type“ shuts the machine off exposures. immediately ( less than 1 sec.)  Caliberated in sixtieths 7 second, correspond to the 60 cycle/second alternating current each 1/60 = one pulse. 3- Film a- Speed  The fastest and most appropriate film should be used.  Dental film speed are described A, B, C, D, E.  A, B, C  the slowest and not used today.  E  being the fastest and require 1/2 exposure- required for D.  E+  fast as E and good quality as D. b- Screen  Extra-ral films used intensifying screen to reduce patient exposure How?  Patient exposure during extra-oral projection can be further reduced? 1. Using high speed (T-Mat grain film) + 2. Using rare-earth intensifying screen. This combination Twice as fast as conventional (Ca-tungastate screen/film) c- Holder  Film holding devices should be used. Why? 1. To avoid using patient finger to hold film in place. 2. To avoid unnecessary dose to finger. 3. More accurately align the film with teeth & BID. 4. Thus avoid retaking radiograph "due to X align).  Film holder is essential for rectangular collimator? 4- Technique a. Lead protective Apron & Thyroid collar Reduces genetic Reduces Thyroid exposure by 98% exp. By 50% b. Using parallel tech. instead of bisecting angle tech. Why? 5- Processing a- Dark room lighting The dark room must be kept: 1. Free from light leaks (e.g. from window, around doors plumbing, air condition…). 2. With appropriate safe-light filter  Red safe light filter (for extra-oral, E+ intraoral).  15 W bulb.  4 feet from working area.  Light orange not to be used fog. b- Processing Method  When radiograph are to be processed by Manual (hand-dip) Method (time – Temp. Method). 1. Full development should be used (5 Mint, 70°F) exposure time can be reduced 25%. 2. Sight or visual development should not be used as it encourage overexposure, undevelopment. c- Processing solution Should be: 1. Changed regularly. 2. Stirred thoroughly twice daily. 3. Kept covered why? 4. Not subjected to high temperature. 5. Checked daily (automatic) weekly (Manual). 6. Chemicals should be replenished. d- Quality assurance program  These should be one staff member who is responsible for monitoring all exposure processing and equipment maintenance daily this preventing future retakes. 6- Viewing: Radiographs should be properly:  Mounted in opaque amounts.  Viewed in a dimly lit room.  Viewed with properly functioning viewbox. To avoid re-takes.  The operator of dental x-ray equipment may be potentially exposed to Scattered rad. Leakage rad. Primary beam (from patient (from tube skull) housing) Methods to reduce occupational exposure: 1) Position and Distance. 2) Shielding. 3) Monitoring. 1- Position & Distance rule a- Rules to avoid primary beam? The operator should stand at least 6 feet (2 meters) away from the patient in a safe quadrant at an angle between (90°-135°) to the primary beam (area of minimum scatter). Should stand behind an appropriate protective barrier or outside the operatory behind a wall. Operator should not hold-films in the patient's mouth  squamous cell carcinoma finger. Operator should never stand in the primary beam to restrain a pt. during x- ray exposure. (a relative or find to patient should dose). b- Rules to avoid scattered radiation:  Scattered radiation from panoramic x-ray unit is relatively small WHY?  Narrow beam.  Narrow collimator. c- Rules to avoid radiation leakage:  Operator should never hold or stabilize tube head or cone during exposure. 2- Shielding (if can not stand 6 feet): Operator should leave the room and stand behind a suitable wall during exposure. The wall: Must be of sufficient density and thickness. Not necessary to be lined with lead. Walls constructed of gypsum wallboard sufficient (for dent office). 3- Monitoring: MPD for occupationally exposed person should not exceed 1 mSV/week. 1 msv/week = 4000 panoramic/week If operator follow position, distance, shielding rule and wear lead Apron. Radiation Dosimetry Monitoring Service  Film badge = contains lithium fluoride crystal. When returned to the company, the badge is processed and compared optically with known amount of radiation, the resulting exposure is reported to dental office. Worn on the clothing over the front of hip or chest. Provides: 1. Way to express concern for reducing and monitoring radiation exposure to staff. 2. Legal documentation that staff member have or have not received excess radiation. 3. Written record of staff exposure in unlikely but possible event that one of the staff members develops cancer and balms it on the office x-ray procedure. A- Primary beam: The primary beam should never directed at any one other than the patient. B- Patient position: The patient should be positioned that the x-ray beam is aimed at a wall of the room and not through a door or opening to where people may be located. C- Shields: The walls and the floors as well as the roof of the x-ray room must contain load fro protection or if thick gypsum. D- Equipment and personnel monitoring: Dental x-ray machine must be monitored for leakage radiation.