Chapter 8 Notes Flashcards
x-ray photons are produced when
high-speed electrons from the cathode strike an anode target
the greater the mass or speed of the incident electrons
the greater the quality (energy) and quantity (number) of photons produced
what are the two target interactions that produce x-ray photons
bremsstrahlung (brems) and characteristic interactions
what percent of the total kinetic energy of the incident electrons produces interactions
less than 1%
what percent of the kinetic energy of the incident electrons is converted to heat
99%
brems interactions occur when
the incident electron interacts with the force field of the nucleus; causes electron to brake and then diverts its course
the photon energy from a brems interaction is
the difference between the entering and exiting kinetic energy of the electron
characteristic interactions occur when
the incident electron interacts with an inner-shell electron; an electron hole is created, making the atom unstable; causes cascade effect
the photon energy of a characteristic interaction is
difference between the binding energy of the outer and inner shells
most photons are produced by what interaction
bremsstrahlung interactions
an x-ray emission spectrum graph illustrates what
relationship between the two target interactions within the primary beam
average primary beam photon has a keV energy of only about _____ percent of the kVp
30-40%
changing kVp changes what
the quality (energy) of electrons striking the target; changes the number of higher-energy photons and the amplitude of the emission spectrum graph
bremsstrahlung makes up what percent of diagnostic x-rays
> 90%
the closer the incident electron gets to the nucleus
the more it brakes and changes direction
the x-axis on the x-ray spectrum represents what
photon energy (keV)
the y-axis on the x-ray spectrum represents what
intensity (number of photons)
bremsstrahlung radiation produces a _____ spectrum
continuous
kVp is
peak voltage applied to the x-ray tube
keV is
unit used to measure the energy of x-ray photons
what is the binding energy of the K-shell in tungsten
69.53 keV
must select what kVp for characteristic radiation to be produced with tungsten
70 kVp or higher
beam quality
the penetrating ability of the x-ray beam (energy of the photons produced)
beam quality is controlled by what
the kVp setting
beam quantity
the x-ray beam’s intensity (number of photons actually produced)
what controls beam quantity
mA
increasing mAs or kVp does what to IR exposure
increases it
increasing distance or filtration does what to IR exposure
decreases it
what target material do mammographic tubes use
molybdenum
changing the kVp does not change the energy of
the characteristic x-rays
as kVp increases
so does average energy
as mA is doubled
the energy doubles
as filtration is increased
the x-ray intensity decreases, but effective energy increases
as the pulse phase increases
the number of x-rays and x-ray energy increases
increasing kVp does what to the graph
graph shifts to the right and up
increasing mA does what to the graph
graph shifts up
increasing filtration does what to the graph
graph shifts to the right and down
improving the generator does what to the graph
graph shifts to the right and up
as current (mAs) is increased
quantity is increased
as voltage (kVp) is increased
quantity and quality increase
as filtration is increased
quantity decreases, but quality increases
as target atomic number increases
quantity and quality increase
as voltage ripple increases
quantity and quality decrease
