Test 2 - Chpt 6 & 11 Flashcards
Two interactions that occur in the tungsten target
Characteristic
Bremsstrahlung
How does heat production occur
When the electrons interact with the outer shell electrons of the tungsten target they cause excitation which causes excess energy to give off as infrared radiation (heat)
Characteristic Interactions
Filament electrons enters a target atom and strikes an orbital electron
How does characteristic interactions create photons?
If k shell electron is removed from orbit then an electron from the L shell drops to fill the vacancy. It does this by expending some of its PE which is given off as a photon
What shell is most likely to fill an inner shell
Adjacent shell
For characteristic photons, energy is dependent on the difference of what?
Of the binding energy between the shells involved
Characteristic photon is named for the what?
For the shell being filled in each case
K characteristic = L electron filled a K vacancy
How to find the energy of a characteristic photon
Binding energy of the farther shell is subtracted from that of the closer shell
(Inner shell - outer shell = photon energy)
What must happen for an orbital electron to be removed
Filament electron must have KE equal to or greater than the binding energy of the electron with which it interacts
When the filament electron misses all of the orbital electrons and interacts with the nucleus of the atom
Bremsstrahlung interaction
How is a brems photon created?
When the filament electron slows down and changes direction because of the attraction to the nucleus it loses KE which is released as a photon
How to find the energy of a brems photon
By subtracting the energy that the filament leaves the atom from the energy it had when entering
Why are most of the photons produced brems photons?
- only k shells provide enough energy
- orbital electrons are in constant motion so easy to miss
Where is added filtration placed?
Between the target window and the top of the collimator
Total number of x-ray photons in a beam
Beam quantity
What is associated with beam quantity
Radiation dose
Intensity of a beam is inversely proportional to the square of the distance
Inverse square law
What absorbs low energy photons that do not contribute to the image
Filtration
What is beam quality?
The penetrating power of the x-ray beam
What creates the dark shades of the image?
Photons that reach the image receptor 
What creates the white or clear areas of the image?
Areas where no photons reach the image receptor
The thickness of absorbing material necessary to reduce the energy of the beam to 1/2 its original intensity
Half value layer, HVL
What is the normal HVL of diagnostic beams
3-5 mm Al
The beam that exits the collimator and exposes the patient?
Primary beam
Beam that remains after interaction with the patient and is exiting the patient to expose the IR
Remnant beam
What is formed within the patient due to interactions with matter/tissue?
Secondary photons
For the emission spectrum graph what indicates a change in quantity
Y axis (number of x-rays)
For the emission spectrum graph what indicates a change in the quality
X axis (x-ray energy)
What five factors change the appearance of the x-ray emission spectrum
mA, kVp, tube filtration, generator type, and target material
If you decrease the quantity, what happens to the amplitude of the graph?
It decreases
If you increase mA what happens to the amplitude of both the continuous and discrete portions of the spectrum
Increases amplitude
If you increase kVp, what happens to the amplitude of both continuous and discrete portions of the spectrum in what way does it shift?
Amplitude increases
Shift, right
An increase in tube filtration causes what to happen to the quantity and quality
Decrease in quantity
Increase in quality
What is directly proportional to radiation quantity reaching the patient and the amount of remnant radiation reaching the IR
mAs
What is inversely related to exposure time to maintain exposure to IR
mA
What is directly proportional to radiation quantity
Exposure time
What is directly related to IR exposure
exposure time
Image brightness is adjusted during what and for what?
computer processing
low and high exposure errors
what can exposure errors result in?
increased quantum noise visible
(T/F) Computer processing can fix overexposed, but not underexposed
true
What affects the amount of radiation exposure to the IR?
kVp
Too little radiation reaching the IR increases?
noise
The advantage of using the 15% rule
Changes exposure without changing patient dose
(pregnant women & pathology)
How to maintain exposure when adjusting the kVp by 15%?`
Change mAs by a factor of 2
what is affected when altering the X-ray beams’ penetrating power (2)?
absorption and transmission
increasing kVp does what to contrast?
decreases it
Higher kVp reduces the total number of what and increases what?
interactions
the X-rays transmitted
What does the level of radiographic contrast desired depend on? (3)
- type and comp. of tissue
- visualized structures
- doc’s pref
Focal spot size affects what of the image?
sharpness
(detail/resolution)
What affects the amount of radiation reaching the patient?
SID
What type of relationship does SID and radiation intensity have?
inverse relationship
What is the inverse square law in WORDS >:{
the intensity of the X-ray beam is inversely related to the square of the distance from the source
Changing SID requires a change in what to maintain exposure to the IR?
mAs
Intensity directly relates to the square of what?
the distance
Direct square law AKA
Exposure maintenance formula
An increase in SID affects what (decrease or increase) (2)?
- image distortion decreases
- spatial resolution increases
If you can’t decrease OID how can you make up for it?
By increasing SID
Limiting scatter improves what?
quality and contrast
Why does using a grid increase patient dose?
Need to increase mAs
A larger field size increases what and causes what?
increases the amount of tissue irradiated
causes more scatter radiation
A larger field size does what to contrast? why?
Decreases contrast
- the amount of radiation reaching the IR has increased
exposure techniques and the amount of radiation output depend on what?
the type of generator used
generators with more efficient output require what to produce an image?
lower exposure technique settings
x-ray tubes operated above 70 kVp are required to have a minimum of what?
2.5 mm of aluminum filtration
increasing tube filtration increases the percentage of what?
higher-penetrating X-rays to lower-penetrating X-rays
What is beam attenuation?
What is left after scatter and absorption
part thickness affects what?
beam attenuation
(T/F) increasing or decreasing part thickness requires a change in mAs to maintain exposure to the IR?
True
What establishes the environment for X-ray production?
The removal of the orbital electron
What produces characteristic X-rays once the environment is set?
the expending of energy during the cascade
Will there be K-shell interactions if a radiographer selects a kVp that’s lower than 70?
No, for tungsten it must be equal to or greater than 69.5 keV
(T/F) Bremsstrahlung interactions come from the loss of KE from the filament electron
true
(T/F) The closer the filament electron gets to the nucleus the weaker the attraction
False
-The attraction is stronger
(T/F) The more energy the filament electron gains the stronger the resultant brems photon
False
-The more energy the electron loses
The average energy of a brems photon is what of the kVp selected at the control panel?
1/3
What is the primary contributor to inherent filtration, equating to about 0.5 mm Al Equivalent?
target window
K-characteristic photons’ energy range
57-69 keV
What type of relationship do mAs have with the exposure reaching the IR?
Direct proportional
What type of relationship does mA and time to maintain exposure to the IR?
Inverse Proportional
Given the anatomic part is adequately penetrated, changing the kVp will affect what (2)?
Scattering and contrast
The amount of remnant radiation will decrease when you increase what?
tissue thickness
