radiation protection questions for week 2 Flashcards
define TLD
Thermoluminescent dosimeter
define Use Factor
percentage of time during which the x-ray tube is on and directed toward a particular protective barrier
define Diagnostic protective x-ray tube housing
Protective shielding in the x-ray tube housing designed to reduce leakage radiation to less than 100mr/hr at 1 m
define glow curve
The graphically displayed response of a TLD as a function of temperature
define primary protective barrier
Barrier designed to shield against primary radiation. The image-intensifier assembly serves as a primary protective barrier. Secondary protective barriers are designed to shield areas from secondary radiation and are always less thick than primary barriers
define x-ray linearity
Radiation intensity is proportional to the mA station selected
define secondary radiation
Leakage radiation; scatter radiation
define occupancy factor
Level of occupancy of an area adjacent to x-ray rooms. The concept of the relative time that a protected area is occupied
define Geiger-Muller region
voltage plateau over which the Geiger counter detector operates
define resolving time
Applies to Geiger counter and scintillation detector. The minimum time between two interactions allowing both interactions to be detected
What do audible and visible signals indicate on the radiographic control console?
That the x-ray beam is energized and at what technique
List as many devices used for radiation protection on radiographic equipment as you can
Protective drapes, Bucky slot cover, 5 minute reset timer, exposure switch that fastens to the console, dead-man switch, collimator, filter, tube housing, 6 ft cord on mobile unit
What is the result if the x-ray beam and the film are not properly aligned?
Misalignment causes unintended tissue to be irradiated, and intended tissue to be missed
What filtration is used for mammography equipment operated below 30 kVp
50mr/hr
How are reproducibility and linearity different when the intensity of the x-ray beam is measured?
Reproducibility- requires constant radiation intensity for multiple exposures at a fixed technique
Linearity- implies proportional radiation exposure at adjacent mA stations
What characteristics of fluoroscopic equipment are designed for radiation protection
protective curtain on the image-intensifier tower
Bucky slot cover
5 minute reset timer.
How can filtration be measured it=f the amount of inherent and added filtration is unknown?
Experimentally determine the half-value layer and check to see that it exceeds the minimum HVL’s published by the NCRP
Name the three types of radiation exposure that are of concern when protective barriers are designed
Primary radiation, leakage radiation, and scatter radiation
List 4 factors that are taken into consideration when a barrier for a radiographic room is designed
Use factor, occupancy factor, distance, dose limit, kVp
What is the difference between a controlled area and an uncontrolled area?
Controlled areas- are those primarily occupied by radiology personnel and patients. Normally, workers who enter a controlled area would be provided with an occupational radiation monitor
An uncontrolled area can be occupied by anyone; therefore, the maximum exposure rate allowed is based on the recommended dose limit for the public
What are the units of workload for an x-ray examination room?
mA min/wk
Explain the use factor (U) as it relates to a protective barrier in an x-ray examination room
use factor of a room helps determine whether a given wall or the ceiling is a primary or secondary protective barrier and therefore what protective design is necessary
Why is the use factor for secondary barriers always 1?
Secondary radiation, leakage, and scatter are continuously present when an x-ray tube is energized
Name the three gas-filled dosimeters
Ionization chamber, proportional counter, Geiger-Mueller counter
