Test 2 - part 2 Flashcards
mA’s
milliamperage per second
responsible for xray quantity
used to adjust optical density and contrast
if mA’s are too high
film will be overexposed
if mA’s are too low
film will be underexposed
kVp
kilovoltage peak
refers to amount of energy an xray beam possesses
controlled by electrical potential and voltage
related to degree of xray penetrability
responsible for xray quality
a change in __% in kVp is needed to notice visible film changes
4%
a change in _____% kVp is equivalent to 50% change in mAs
10-15%
____% change in mAs is required to observe changes in optical density
30
reducing time of exposure will result in ______ the patients radiation dose
reduce
relationship between mAs and kVp that results in production of equivalent image density
manipulates the tube voltage by the 10 kVp will result in same image density change by changing the mAs by 50%
10kVp rule
doesnt apply for radiographic images acquired at less than 60 kVp or greater than 100 kVp
blurring of the shadow of an image with lowering of sharp edges corresponding to object shape
increase in focal spot with increase ______
change in ______ is proportional with object film distance
increase film distance increases ______
penumbra
decrease in light or xray intensity is inversely proportionate to square of the distance of the object to the source
light xray exit as a cone and the intensity decreases due to spreading out effect
wavelength remains fixed
radiation intensity is inversely related to the square of th distance from the source
if distance is increased 2x the intensity is reduced by 1/4
when distance is cut by 1/2, intensity is increased by 4x
inverse square law
results with the cloud of electrons emitted from the cathode
thermionic emission
what 3 events occur as electron cloud approaches anode
cathodes electrons lose kinetic energy
99% of interaction of electrons at target result in heat production
remainder of electrons will produce bremsstrahlung or characteristic radiation
photon production increases with _____ in kVp
increase
at 60 kVp - only ____% are x photons
.5
at 100 kVp - ____% are x photons
1
occurs in tube
majority of xrays
electrons emitted from cathode hit the anodes target which contains a high atomic number Z
strong nucleic field of positive charged protons begin to project electrons
some projectile electrons change their course and deflect with some or all of their original kinetic energy being LOST
results in energy released as xray photons known as
bremsstrahlung radiation
german for breaking or slowed down radiation
bremsstrahlung
energy ranging from zero to maximum kinetic energy (Emax) when they hit the anode depending on nucleic field
continuous spectrum wiht peak 1/3 of Emax
bremsstrahlung radiation
occurs in tube
produced when a projectile electron interacts with inner K shell electrons
projectile electrons energy exceeds binding energy of K shell electron resulting in removal of the K electron from its orbit
outer L shell electron will fill the void
this results in energy released as
characterisitc radiation
interaction is very specific, xray photon has specific energy = to difference in binding energies of orbital electrons - in diagnostic xrays, only the K characteristic xray emission is important
characteristic radiation
each element has its characteristic electron binding energy
each characteristic xray will be different
effective energy of characteristic xrays is directly related to atomic number Z of particular element
characteristic elements
energy of different photons emitted from xray tube
xray emission spectrum
contains precise fixed energies and form descrete emission spectrum
characteristic xrays
