Radl 70 Protection of Personnel
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If a pt has to be held for an xray what does the holder have to do?
- remain at right angles to the pt
- wear protective lead garments
what are the three main things to remember about personnel protection?
are time and radiation exposure directly proportional?
what is the most effective way to reduce radiation exposure?
what is the equation of the inverse square law?
what happens to intensity when distance is halved? when distance is doubled?
- increases by 4 times
- decreases by 1/4
why is lead the primary element for shielding?
- high atomic number - 82
- majority of scattered photons are absorbed
what are two types of barriers?
what is a primary barrier?
wall or other area struck by the primary beam
how high must a primary barrier be?
what is a secondary barrier?
- absorbs scatter radiation
- beam cannot be directed toward this
what are some examples of secondary barriers?
- control booth (except in california)
how thick does a lead apron have to be at 100 kvp and used as a secondary barrier?
how thick does a lead apron have to be if used as a primary barrier?
how thick do lead gloves have to be?
how thick are lead goggles have to be?
what are some structural shielding used for?
- primary and secondary radiation
- controlled/restricted areas
- uncontrolled/unrestricted areas
- leakage radiation
what is the maximum weekly dose in a controlled/restricted area?
- 100 mrem
- limited access
- an area with an active source of radiation
what is the maximum weekly dose in an uncontrolled/unrestricted area?
- areas accessible to general public
what factors are used to determine barrier thickness?
- use- U
- workload- W
- occupancy- T
what determines the "use" factor when determining barrier thickness?
full use -1 (floors, walls, ceilings exposed routinely to primary beam)
partial use - 1/4 (doors, walls, floors of dental equipment not routinely exposed to primary beam)
occasional use - 1/16 (ceilings not routinely exposed)
what determines the "workload" factor when determining barrier thickness?
- mA minutes or seconds per week
- total radiation output time during the week
- beam-on time for that particular x-ray tube
what determines the "occupancy" factor when determining barrier thickness?
- how the area on the other side of the protective barrier will be used
- Full-1 (areas of heavy use)
Partial-1/4 (areas of some use)
occasional-1/16 (areas of very limited use)
how much radiation cannot leak out of the protective tube housing?
100 mR/hr at a distance of 1 meter from x-ray tube
how thick should the protective curtain in fluoro be?
.25 mn lead
how thick should the bucky slot during fluoro be?
.25 mm lead
where can the 2nd badge on a pregnant tech be worn?
beneath the lead apron at waist level
what are the types of personnel dosimeters?
- film badge
- pocket ionization chambers
- thermoluminescent dosimeters (TLD)
A film badge consists of what 3 parts?
- plastic film holder
- metal filters
- film packet
what type of radiation can a film badge read?
how accurate is the film badge?
10mrem - 500 rem
what are the advantages of the film badge?
- lighweight, durable, portable
- cost efficient
- permanent legal record
- can differentiate between scatter and primarry beam
- can discriminate between x, gamma, and beta
- can indicate direction from where radiation came from
- control badge can indicate if exposed in transit
what are the disadvantages of the film badge?
- only records exposure where it's worn
- not effective if not worn
- can be affected by heat and humidity
- sensitivity is decreased above and below 50 keV
- exposure cannot be determined on day of exposure
- accuracy limited to + or - 20%
what are the two types of pocket dosimeter?
- non self-reading
what are the advantages of the pocket dosimeter?
- small, compact, easy to use
- reasonably accurate and sensitive
- provides immediate reading
- detects gamma or x radiation
what are the disadvantages of the pocket dosimeter?
- readings can be lost
- can only be read once
- must be read each day
- no permanent record
- susceptible to false readout if dropped or jarred
what are the advantages of the thermoluminescent dosimeter (TLD)?
- crystals contained in TLD interact with ionizing radiation as tissue does
- determines dose more accurately
- more accurate than film badge
what are the disadvantages of the thermoluminescent dosimeter (TLD)?
- costs more than a film badge
- can only be read once
- records exposure only where worn
what are some types of survey instruments?
- ionization chamber - cutie pie
- proportional counter
- Geiger-Muller detector
- Calibration instruments
what does the ionization chamber measure? and how much?
- measures x or gamma and beta
- measures intensity from 1mR/hr to several thousand R/hr
what is the ionization chamber mostly used for?
to measure patients recieving brachytherapy or diagnostic isotopes
what does the proportional counter measure?
beta or alpha radiation in laboratories
what is the Geiger-Muller detector used for?
generally used for nuclear medicine facilities
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