Chapter 13 and 15 Flashcards
When the X-ray photon interacts with an inner shell electron and ejects the electron and is totally absorbed in the interaction.
Photoelectric absorption
Coherent scatter is also called
Classical scatter
Thomson scatter
Unmodified scatter
When X-ray photons interact with orbiting electrons causing them to vibrate
Coherent scattering
Which interaction uses very low energy and is not seen in diagnostic X-ray?
Coherent scattering or Thomson
When incident photons interacts and removes a loosely bound outer shell electron.
Compton scattering
In Compton scattering, the incident photon loses up to ___ of its incoming energy and proceeds in a new direction causing scattering.
1/3
Which interaction requires very high energy photons?
Pair production
When photons come in and gets close to the nucleus of the atom losing all of its energy in the process.
Pair production
Which interaction requires very high energy photons above 10 MeV?
Photodisintegration
Which 2 interactions have effects on X-ray images?
Photoelectric absorption
Compton scattering
As kVp increases, photoelectric absorption ____
Decreases
As KVP increases, Compton scatter ____
Increases
Which 2 situation will photoelectric be found?
Lower KVP ranges (40-70)
When contrast agents are introduced
Factors contributing to Compton scatter are
KVP
Volume of irradiated material
An increased KVP will ______ patient dose
Decrease
A decreased KVP will ____ the dose
Increase
Volume of irradiated material includes
Field size
Patient thickness
Average tissue density
An increased FS will _____ volume of tissue irradiated
Increase
Increased FS results in ______ scatter
Increased
Decreased FS will _____ beam quantity
Decrease
Thicker body parts produce ____ scatter
More
______ devices can be used to improve spatial resolution and contrast.
Compression
Beam restrictions include
Aperture diaphragms
Cones
Cylinders
Collimators
Ancillary devices
The reduction in the number of X-ray photons in the beam, and subsequent loss of energy, as the beam passes through matter.
Attenuation
When an X-ray beam passes through matter, it goes through a process called
Attenuation
The center of the atom is a positively charged nucleus containing
Protons and neutrons
The energy required to remove an electron from a shell is termed the
Binding energy
The average atom in the soft tissue of the body has an approximate k-shell binding energy of only
0.5 kev
What are the 5 interactions between X-ray and matter
Photoelectric absorption
Coherent scattering
Compton scattering
Pair production
Photodisintegration
kVp affects the ___ of the beam
Penetrability
Which factors contribute to Compton scatter?
KVp and patient thickness
Are scatter photons part of the useful beam?
No
What does a decreased field size do to beam quantity?
Decreases it
The thicker the body part the _____ scatter
More
_____ and _____ increase the number of interactions
Thickness and density
_____ body parts produce more scatter
Denser
Compression devices are used to improve
Spatial resolution And contrast
Decreasing part thickness results in _____ patient dose
Lower
Decreased OID improves
Spatial resolution
Ideally, beam restrictors decrease ______ to anatomy of interest
Field size
There are 2 sets of _____ that permit infinite number of field sizes
Shutters
The bottom shutters reduce
Penumbra
Geometric unsharpness around periphery of image
Penumbra AKA edge unsharpness
______ radiation occurs from areas of the X-ray tube other than focal spot area
Off focus
Off focus radiation produces images beyond
Exposed field of radiation
The light field needs to be accurate within
+/- 2%
PBL stands for
Positive beam limitation
______ degrades image quality by placing exposures on the IR that are unrelated to patient anatomy (fog)
Scatter
Automatically collimates beam to size of image receptor
PBL
The upper shutter reduces
Off focus radiation reaching IR
What is the most common beam restrictor?
Collimation
Compression bands are routinely used in
Mammography
For radiographers to get the best possible image we must minimize the amount of ____ reaching the IR
Scatter
•An image is created when
some photons pass through unaffectedwhile others are absorbed
The more photons that pass through unaffected, the _____ IR exposure
Better
The volume of irradiated material is controlled by
field size and patient thickness
As volume increases, scatter
Increases
The higher the atomic number is, the ______ photoelectric absorption and ____ scatter
More
Less
What 3 things absorb radiation and cause a high contrast image when used
Barium
Iodine
Lead
_____ should never be greater than IR size
Field size
flat sheet of metal (lead) has opening in the center and attaches to the x-ray tube port
Aperture diaphragms
Device placed between the patient and IR
Grid
