Exposure Factors Flashcards
Exposure factors
These are factors which affect the quantity and radiation energy to which the image receptor is exposed
Exposure factors depend on what?
-Thickness of the region
-Region being examined
- intensifier screen
-pathology
- density of the region
Examples of exposure factors.
- Kilo voltage peak
- milliampere
- exposure time
- filtration
- focal spot
- ffd
- collimation
Kilovoltage (kvp)
Controls the quality of x-ray photons through the body
Quality
Penetration power of photons
Density/quantity
This refers to the degree of darkness on an x-ray film.
Effects of quality (penetration power)on photographic film.
- Influences the ability of an x-ray beam to penetrate matter.
- influences radiation dose in a patient
-influence the radiographic contrast of the image
Focus to film distance.
distance from the radiation source to the IR
FFD in relating to intensity
when the ffd increases the lower the intensity of radiations reaching the film
What to consider when choosing FFD
the x-ray tube should not be close to the patient
short FFD’s give unacceptable geometric unsharpness
intensifying screens
screens that produce visible light after x-rays hit them.
inside the cassettes, are placed side by side with a film between them
types of intensifying screens.
slow screens; high resolution radiographs, high kvp and mAs.
fast screens; low resolution, low kvp and mAs
Rare earth; faster than fast screens, low resolution, low kvp and mAs
Secondary radiation grid
a device that is placed between the patient and the x-ray film or IR.
absorbs the scattered radiations.
air gap techinique
a patient is not in direct contact with the IR rather some Cm away
Focal spot
point source of x-rays basically on the anode
collimation
field area for the x-ray to hit, its adjustable
filtration
the removal of low energy x-ray photons which do not contribute in image quality
types of filtration
inherent; components in the x-ray tube absorb some low energy x-ray photons.
added filtration; manually added sheets of metal to absorb low energy photons.
What is the difference between voluntary motion and involuntary motion.
Voluntary motion is visualized as a generalized blurring of linked structures while involuntary motion is identified by localized unsharpness or blurring
Image quality factors
- Density
- Contrast
- Spartial resolution
- Distortion
Distortion
Misrepresentation of anatomical size and shape
Controlling factors of distortion
- Source image distance ( SID)
- Object image distance ( OID)
- Object alignment on IR
- Cr alignment
