Chapter 5 Radiation Protection Flashcards
An instrument that reads film from badge. It is used to measure the optical density, the intensity of light transmitted through a given area of the dosimetry film, and compares it with the intensity of light incident on the anterior side of film.
Densitometer
Sent by monitoring company– serves as a basis for comparison with the remaining film badges after they have been returned to the monitoring company for processing
Control Badge
What does a film badge record?
Whole body radiation exposures accumulated at a low rate over a long period of time
What are the 3 parts of the film badge?
- durable lightweight plastic film holder
- assortment of metal filters
- film packet
Sensitivity range of the film badge?
0.1 mSv (10 rem) to as high as 5000 mSv (500 rem)
What is the main advantage of the film badge?
It’s cheap
What type of radiation does the film badge monitor?
low energy x-radiation, gamma radiation, and beta radiation
What is the disadvantage of the film badge?
Temperature and humidity extremes can cause fogging
What is the most common type of personnel monitoring device that replaced the film badge?
Optically Stimulated Luminescence (OSL)
What type of detector is used in OSL?
aluminum oxide
How is an OSL read out?
Laser light at selected frequencies
What are the three types of filters used in an OSL?
- Aluminum
- Tin
- Copper
What’s the sensitivity range for the OSL?
1mrem for x-rays and gamma ray photons with energies ranging from 5KeV to greater than 40 MeV
What is the most sensitive type of personnel dosimeter?
Pocket Ionization Chamber
What do pocket ionization chambers required to have with it?
special charging unit
What is the sensitivity range of pocket ionization chambers?
0 to 5.2x10^-5 C/kg (0-200mR)
What is the advantage of using a pocket ionization chamber?
It provides an immediate exposure read out for worker whos work in high exposure areas
What is the disadvantage of using a pocket ionization chamber?
If it is not read each day it may give inaccurate reading because electrical charge tends to escape with time and give false readings and jarring and shock could discharge it
What is contained in the Thermoluminescnt Dosimeter(TLD)
Crystalline a form (powder or small chips) of lithium fluoride
How is TLD read out?
Passing crystals through special heating process
What intensity of light is proportional to in TLD?
The amount of radiation that has interacted with crystals
What’s the advantages of a Themoluminescnt Dosimeter?
Over the film badge is that the crystals interact with ionizing radiation as human tissue does making it more accurate
What are the disadvantages of using a Thermoluminescnt Dosimeter?
The high cost, can only be read once, the readout process destroys the stored information
When is personnel exposure monitoring required?
Whenever radiation workers are likely to risk receiving 10% or more of the annual occupational EfD limit of 50 mSv (5mrem)
What does personnel dosimeter determine?
Occupational exposure by detecting and measuring the quantity of ionizing radiation to which the dosimeter has been exposed over a period of time
Where is the personnel dosimeter to be worn at?
Front of the body at collar level
What procedures produce the highest occupational dose?
fluoroscopy and special procedures
How much more dose the unprotected parts of the head area vs parts under the lead apron
10-20xs
When is an extremity dosimeter recommended?
by imaging professionals performing fluoro procedures that require the hands near the primary x-ray beam
Where should an extremity dosimeter be worn at?
finger
When might you be required to wear2 monitoring devices?
during special computed radiography, digital radiography, or conventional radiographic procedures
or if you’re pregnant
Where should the 2 monitoring devices be worn at?
- first at collar (primary) outside the lead
- 2nd beneath wrap in the trunk area or at abdomen under the lead
What characteristics must personnel dosimeter posses?
- lightweight and easy to carry
- made of materials durable enough to tolerate normal daily use
- has to be able to detect both small and large exposure inconsistent timely manner
How penetrating radiations and soft scatter radiations will appear different on a film badge
Penetrating radiations cast faint shadow on film and soft radiations(scatter) shows more pronounced image
On the filter of the film badge how it appears when exposure is from excessive amounts of scatter?
fuzzy image from scatter of different angles
ON the filter of the film badge how it appears when exposure is from single exposure from primary beam?
sharply defined beam
Know why a control badge should always have a zero reading
It is to be kept in a radiation free area within imaging facility
What is included on a personnel monitoring report/
Personal data, type of dosimeter, radiation quality, equivalent dose data, cumulative equivalent doses, and inception date
What does the letter M signify on a personnel monitoring report?
An equivalent dose below the minimum measurable radiation quantity was recorded during that time
Who receives and reviews the personnel monitoring reports?
Radiation Safety Officer
What filter in an OSL absorbs the leas?
Aluminum
Which filter is an OSL attenuates the most?
copper
Know which type of pocket ionization chamber is the most common
self reading
Know where each electrode 9positive and negative) is located on pocket ionization chamber
- positive charged (central electrode)
- negatively charged (outer electrode)
What is the function of the material contained within the TLD?
- Sensing material of the TLD
- Radiation causes that LiF crystals to undergo charges in some of their physical properties
