Imaging System Characteristics Flashcards
Dual focus Tubes mm small and large:
small
- 0.5mm
- 0.6mm
- 1.0 mm
large
- 1.0mm
- 1.2mm
- 2.0mm
- 0.3/1.0mm is typically used for :
- 0.1/0.3mm is typically used for:
- angiography and magnification procedures
- mammography
What is Microfocus Tubes:
FSS of 0.3mm or less
Large focus
- normal imaging
- higher mA can be impressed for larger/dense body parts
What is the main advantage of large FSS in relation to detail?
Shorter exposure times to minimize motion
Small focus
- given amount of electrons cover smaller area on anode
- cannot use high mA due to limited heat capacity
- used for magnificatoin radiography where detail is required
- for smaller and thinner body parts
Filtration
Filtration
X-ray beam is ___________ and ___________
- polyenergetic
- heterogeneous
Filtration __________ the beam
hardens
- makes beam more uniform by removing softer rays
What are the two classifications of filtration?
- Inherent
- Added
- does not have ability to manipulate
What is inherent filtration made of?
glass or metal envelope (0.5mm Aluminum equivalent)
What is added filtration?
mirror in collimator box (1.0mm Aluminum equivalent)
- another 1.0mm AI eq added between x-ray tube housing and collimator
What is the total of inherent and added filtration?
.5mm of Inherent Filtration+ 2.0mm of Added Filtration=
2.5mm of Total Filtration AI equivalent
Half-Value Layer (HVL)
- improves quality of the beam
- is the amount of material that reduce the intensity of the x-ray beam to half its original value
- used for shielding and filtration
- increase in HVL increases the quality of the beam
Compensation Filter
Different shapes of Aluminum mounted under the variable light aperture (collimator)
Compensation filter _________ intensity of x-ray beam for a more uniformed exposure to the image receptor
Balances
What are the two different shapes of compensation filter?
- Wedge filter
- Trough Filter
*does have ability to manipulate
Wedge filter is good for:
body parts thick on one end and thin on the other
ex) foot, hips
Trough Filter is good for:
chest
Anode Heel Effect
- phenomenon which intensity of x-ray beam is greater towards the cathode side of the tube
- the loss of intensity is a result of the electrons traveling farther to the anode heel portion of the target
Where would you place the thicker part of the body?
At the cathode end
