arrt review: radiation physics Flashcards
where is kVp applied in the x-ray tube? what does this do?
to the cathode filament, repels the thermionically induced e- away from the cathode
(low/high/direct) current is required to induce thermionic emission within the cathode filament
high
the maximum energy of bremsstrahlung photons is controlled by what technical factor?
tube potential (kVp)
the maximum energy of a brems photon that can be created during an x-ray exposure is equal to the
energy of the incident electron
a characteristic photon’s energy depends on what 2 variables?
energy of incident electron
binding energy of orbital electrons
a brems photon’s energy depends on what 2 variables?
energy of incident electron
proximity of incident electron to the nucleus
energy of a brems x-ray photon is equal to the _____________
difference between incoming and outgoing electron energy
How does increasing energy affect frequency & wavelength?
Increasing energy = increase frequency, decrease wavelength
main controlling factor for beam quantity
mAs
main controlling factor for beam quality
kVp
can kVp also be an influencing factor for beam quantity?
yes
which tissue interaction is responsible for patient dose? tech’s dose?
patient = photoelectric
tech = compton
attenuation includes __________ (not ________)
scatter and absorption, not transmission
photoelectric in and out
photon comes in, electron goes out
photon is completely absorbed
does ionization take place in photoelectric effect?
yes
does ionization take place in coherent scattering?
no
coherent scattering in and out
photon in, scattered photon out
Compton scattering in and out
photon in, electron and reduced/scattered photon
photon partially absorbed
does ionization take place in Compton scattering ?
yes (plus photon scattering)
as part thickness increases, attenuation _________
increases
as tissue density increases, attenuation _________
increases
as atomic number increases, attenuation _________
increases
as kVp increases, attenuation _________
decreases
Which interaction is least likely to happen in diagnostic rad?
coherent scattering
Coherent scattering
Patient dose
Occupational dose
Image quality
Patient dose = yes
Occupational dose = no
Image quality = bad (scatter, decreases contrast)
Photoelectric effect
Patient dose
Occupational dose
Image quality
Patient dose = yes
Occupational dose = no
Image quality = Good (creates contrast)
Compton scattering
Patient dose
Occupational dose
Image quality
Patient dose = yes
Occupational dose = yes
Image quality = bad (scatter, decreases contrast)
as kVp increases, photoelectric effect _________
decreases (less absorption occurs)
