what does higher kVp do to x ray beam quality
why
it reduces contrast
because at higher kVp, tissues penetrate more uniformly
what type of radiation is seen here
Brem
what is essentially happening with bremstralung radiation (3)
electron shot towards nucleus of Mol target
e is slowed down
that kinetic energy is converted into an x ray
what type of radiation is happening here
characteristic radiation
what type of radiation is happening here
characteristic
what is essentially happening with characteristic radiation (3 steps)
an electron hits an electron in the k shell of an atom
that ring becomes vacant and another electron has to fill it
the energy from going from an outer shell to an inner shell is converted into an electron
what are the shell names from outer to inner
what has more energy here in terms of ring
M, L, K
K has the most energy, so when you go from low low to high, higher energy x ray (from M to K, L to K is less severe)
what is the effect on atomic number on x ray interactions
what is an anatomical way to understand this
higher Z = more likely to be absorbed
bone has a higher Z (ca) than air (H), so it shows up WHITER, aka more is absorbed
do you harden or soften x rays by raising kVp
what does this do to penetration
what does this do to pt dose
you harden them
increases it (they go THROUGH harder, and miss the pt)
decreases pt dose
what does increased mAs do to the image quality
decreases SNR (signal to noise ratio and makes things less grainy)
what is focal spot
what does decreasing it do
area on the anode target that actually produces the x rays when hit
reduces penumbra
what do grids to do image quality and why
what do they do to patient dose and why
they improve it by getting rid of scatter by their design to only let primary rays through
they increase it because you have to increase the mAs to compensate for the photons lost to the grid to get a useful diagnostic image
which is better or worse for the body (harder or softer), and which has a higher kVp
bottom is better, more hard
it probably has a higher kVp
if the ___ is the same, the exposure is the same
mAs
where are the 2 places beams get filtered
inherently before even leaving the house
added with a piece of Al between the window and collimator
what does a collimator do
what does this do to patient dose
what does this do to image quality and why
restricts where the beam is to only clinical interest via shutters
decreases it
improves it by reducing scatter
high energy photons get _____ to…
low energy photons get ____ or ___-
transmitted, to form the image
absorbed or scattered
what do filters essentially do to the image quality and why
they decrease contrast because you are beam hardening and attenuating soft rays that would have been absorbed by the patient (which soft beams are attenuated much much more contrastingly than hard beams, which attenuate similarly among structures)
hard beams, aka __ kVp, attenuate…
this means ___ contrast
high kVp, all the same…
low contrast (when hoes all the same bc theyre jacked up trying to get that hard mean become difficult to distinguish from each other)
what are compensation filters for
what part of the body are they associated with
the thinner parts, gotta harden those beams so they aren’t overexposed. have too much contrast compared to the thiner part of the body
is Rayleigh bad
what type of radiation is this considered and why
how do you reduce this
yes
it is when the atom is excited by an x ray and radiates energy, but does not ionize but instead emits a photon in a different direction than initially which scatters
crank up the voltage
what do SID and. SOD do to image quality and patient dose (they do the same but WHY are they different)
what does OID do to image quality and patient dose
increase quality and decrease dose- SID bc of inverse square law and SOD bc beam spreading
decreases image quality with no effect on pt dose
when you increase image quality, what 2 things are you reducing in terms of SID,SOD,OID
decreasing magnification and penumbra
what is the photoelectric effect
what are the 3 steps
COMPLETE absorption of an X ray photon by an atom
photon hits an inner shell electron
that energy is absorbed by the electron, which gets ejected
an outer electron fills the vacancy and radiation is emitted
