Chapters 6 and 7 Flashcards
Which of the following makes up the majority of the x-ray beam?
Bremsstrahlung.
Most of the electrical energy used to produce x-rays results in
heat
Filament electrons interact with target atoms to produce x-rays in the following two ways
-charecteristics interactions
-bremsstrahlung (brem) interactions
-majority of x-rays have brems
Excess energy is immediately given off as what radiation
infrared (heat)
Characteristics interactions involve what?
-filament electrons
-an orbital electron of a target atom
What shell is most important
k shell
What is the binding tungsten energy for the k shell
69.5 keV
Energy
a characteristic or dependent on the difference in binding energy between the shells involved
The closer the interaction with the nucleus =
more energy lost (brems photon)
higher kVp=
higher brem photon
Highest number of x-ray photons produced will be ____ of the kVp you select
1/3
Quantity
-number of photons in x-ray
-intensity
Inherent filtration
-housing
-window absorbs some of the x-rays
-the target window is the primary contributor
Added filtration
-comes in the form of another 2.0 Al placed between the target window and the top of the collimator
Total filtration
-2.5 mm is the total filtration needed
Beam Quantity
-kVp has bigger impact =15% rule
-the total number of x-ray photons in a beam
-affected by mAs, kVp, distance, & filtration
-varies inversely as the square of the distance
Quantity is associated with
radiation dose
To adjust quantity you adjust the
mAs
-first to adjust-least effect
If kVp is doubled then intensity (quantity) increases by a factor of _____
four
Filtration
reduces patient dose by filtering out low energy x-ray photons
Beam Quality
-the penetrating power of the x-ray beam
-affected by kVp and filtration
Penetration
-refers to those x-ray photons that are transmitted through the body and reach the image receptor
Beam Quality Relationship
-goes up in kVp means increased frequency &
shorter wavelength =more penetration
As kVp increases, the beam’s ability to penetrate matter also _________
increases
Half Value Layer (HVL)
the thickness of absorbing material necessary to reduce the energy of the beam to one half its original intensity
What is the normal HVL of a diagnostic beam
3-5 Al
Higher kVp =
higher HVL
Primary Beam
refers to the x-ray beam as it is upon exiting the collimator and exposing the patient
controlled by quantity (mAs) and quality (kVp)
Remnant Beam
-refers to the x-ray bean that remains after interaction with the patient and is exiting the patient to expose the image receptor
Remnant beams are made of
primary and secondary radiation
X-ray Emission Spectrum
-SID and OID does nothing with the emission spectrum or graph
-grid does not have to do with emission spectrum
Emission Spectrum: characteristic photons are
discrete
Emission Spectrum: Brems photon are
continuous
Continuous Emission Spectrum
-majority of emission spectrum
-brems photons create a bell-shaped continuum
Increase mAs =
-increase amplitude
-also increases photons
-direct relationship
5 Factors that change the appearance of the x-ray emission spectrum:
-mA
-kVp
-tube filtration
-generator type
-target material
An increase in mA increases the amplitude of both the ___________&_____________ portions of the spectrum
-continuous
-discrete
Changes in kVp effect beam
-quality & quantity
-increases the amplitude of continuous & discrete and shifts the wave to the right
Process of outer-shell electrons filling inner-shell vacancies continues down the line creating a cascade effect called
characteristic cascade
So long as kVp is greater than 69.5, what will happen?
characteristic
Bremsstrahlung means?
braking radiation
Penetration
x-ray photons that are transmitted through the body and reach the image receptor
What are the interactions that happens in the tube
-Bremsstrahlung
-Characteristic
Classical interactions (coherent or thomson scattering)
-decreases contrast in image (more grey)
-no ionization
-low kVp = low energy
-minimal patient dose
Compton interactions
-has ionization
-higher kVp
-has scatter
-has occupational dose (tech gets radiation dose)
-has patient dose
-creates secondary photon
-does not depend on atomic number, it relates to the energy of the photon
Photoelectric interactions (very low probability)
-no scatter, everything gets absorbed in the body
-has ionization
-lower kVps
-increases patient dose
-has secondary photon
(not good for the patient, no effect on operator, image quality is good)
Differential absorption
difference between the x-ray photons that are absorbed photoelectrically and those that penetrate the body
Transmission
x-ray photons that pass through the body and reach the image receptor
Absorption
photons that are attenuated by the body and do not reach the image receptor
Radiopaque (spine)
body structures that readily absorb x-rays
Radiolucent (lungs)
less dense structures have a much lower probability of absorption
