Designing for radiation protection Flashcards
Diagnostic-Typed protective Tube Housing
This is required for both the radiographer and patient from off focus or leakage radiation by restricting the emission of x-rays to the area of the useful or primary beam.
Diagnostic-Typed protective Tube Housing leakage has to be:
Reduce the leakage to less than 100 mR/hr at 1 m from the protective housing.
Bucky slot cover: how thick and what is it made of?
0.25mmPb
Protect curtain: how thick and what is it made of?
0.25mmPb
what factors Affecting Barrier Thickness?
distance, occupancy, controlled area vs uncontrolled area, workload, use factor, kvp
What are primary barriers?
lead and concrete
What are secondary barriers
leakage radiation, scatter radiation: steel, glass, gypsum, wood
The x-ray beam and light beam must coincide to within ____ of the SID.
2%
Positive Beam Limitation (PBL) – automatic light localizer must be within __ of the SID
2%
Source-to-image distance indicator – SID indicator must be provided, and must be accurate within ___.
2%
filtration
Reduces exposure to the patient’s skin and superficial tissue by absorbing most of the lower energy photons.
change in beam quality due to filtration is referred to as:
“hardening” of the beam.
Two types of Filtration available:
Inherent filtration and Added filtration
Added filtration:
Usually consists of sheets of aluminum (or its equivalent) of appropriate thickness.
Where is added filtration located:
outside the glass window of the tube housing above the collimator shutters
Readily accessible to service personnel
Total filtration should be at least:
2.5mm Al.
Mobile diagnostic units and fluoroscopic equipment also require________________ total permanent filtration when the tube is operating over 70 kvp
2.5-mm aluminum equivalent
What is the most widely selected as filter material because it effectively removes low energy?
aluminum
positive stuff about aluminum
lightweight, relatively inexpensive and readily available
Compliance with the Radiation Control for Health and Safety Act of 1968 states
diagnostic x-ray beam must always be adequately filtered.
Total filtration equals:
Inherent filtration plus added filtration
ability of x-ray units to duplicate certain radiation exposure for any given combination of kilovolts at peak value (KVP).
Reproducibility
ability of the output radiation intensity at a select Ma value should remain constant (mAs)
Linearity
The variation in x-ray intensity should not exceed ___. (reproductivity)
5%
linearity should not exceed ____ change in intensity from one mA station to the adjacent.
10%
Provide radiation shielding for both imaging department personnel and the general public.
protective barrier
three Categories of radiation sources can be generated in an x-ray room
Primary radiation, secondary radiation, and leakage radiation
Two categories of secondary radiation:
scatter and leakage radiation