Xray Physics Flashcards
a unit of ionizing radiation that is 99% heat and 1% diagnostic
roentgen ( xray photon)
REM
roentgen equivalent in man (tech dose)
5 REMs is safe dose per year
MPD
maximal permissable dose (badges)
number of REMs a person can get in a lifetime without getting radiation poisoning
RAD
roentgen absorbed dose (in anything)
used to identify radiation in patients
measures radiation being absorbed
what are the different forms of primary radiation
bremsstrahlung
and
characteristic
which primary radiation comprises the most photons and interacts with the NUCLEUS of the cell
bremsstrahlung
which primary radiation contains the most energy and interacts with the INNER SHELL of the cell and an outer shell electron fills its spot
characteristic
what are the different forms of secondary radiation
Compton
and
thompson
which secondary radiation interacts with the OUTER SHELL and LOSES energy
Compton
which secondary radiation has EQUAL energy exchange within the cell
Thompson
which form of radiation is also called classical
Thompson
filters are made up of what
aluminum
grids are made up of what
lead strips
what supports the emulsion with silver bromide and halide crystals
film base
what light is considered safe for X-ray use
red light
what is the X-ray process
develop
fix
wash
dry
(DFWD)
don’t forget wash/dry
what tissues are most radiosensitive (mutate)
blood (WBC) , sperm
what tissues are least sensitive (death)
nerve, thyroid, ovaries
what does the developer do
brings out the latent image by developing the exposed silver halide crystals to metallic silver
reduces the amount of exposed silver crystals
what does the fixer do
neutralizes developer
removes unexposed crystals
hardens the image
brown or greasy discoloration to film is caused by what
poor washing
brown or yellow film is caused by what
old developer
“old yeller”
if film is unexposed and developed it will be __
translucent
if film is exposed and developed it will be __
black
spider appearance on the film is caused by what
static
small dots on the film are caused by what
water droplets
corner clipped off on the film is caused by what
copy of film
vertical lines on the film are caused by what
dirty rollers or static grid
scratchy border around the film is caused by what
old screen
contrast = ?
kvp
density = ?
mas
quality of X-rays is
kvp
quantity of X-rays is
mas
darkness of the film is controlled by
mas
if you change 15% of kvp, you must change mas by
30-50%
what is the inverse square law
the dose is proportional to the inverse of the square of the radius. Thus if you double the distance you reduce the dose by a factor of four
FFD to mas
shades of the film are controlled by
kvp
what is the total amount of filtration
2.5 mm
what does SID, FFD and OFD mean
source image distance
film focal distance
object film distance
increased detail on film is noted with what
increase FFD decrease OFD umbra small crystals small focal spot
decreased detail on film is noted with what
decreased FFD increase OFD penumbra large crystals large focal spot
what is in the emulsion in the film
silver bromide and halide crystals
the protective housing of the xray tube is made of what
lead
cathode is positive or negative charge
anode is positive or negative charge
cathode - neg
anode - pos
what does the cathode consist of
large filament
small filament
focusing cup
what serves as the source of electrons in the production of X-rays
filament
filaments are made of what
tungesten
what occurs when a current is applied to the filament
thermionic emission
what is part of the cathode that encases the two filaments
focusing cup
where does thermionic emission occur
focusing cup
electrons move from __ to __ in the xray tube
cathode to anode
why does the anode rotate
dissipate heat
the focal spot on the anode is determined by what
size of filament
what is the line focus principle
makes the focal spot size appear smaller
decreases the target angle which decreases the spot
what heats the filament causing a boiling off of electrons
mA
it takes a minimum change of mas by ___% to see minimum change in density on the film
30%
if mas is doubled then the density is ___
doubled
what is the force applied to accelerate electrons from cathode to anode
KVP
low kVP means __ energy and __ penetration
low energy
weak penetration
what is the difference in density between to structures
contrast
what controls contrast
KVP
increase in KVP causes a __ in contrast
decrease
low KVP produces __ scatter and __ radiation to the patient
decreased scatter
increased radiation
what is another term for low contrast
long scale
to lower contrast, (__ scale of contrast)(more shades of __) you must do what
long scale
more shades of grey
increase KVP by 15% and decrease MAS by 50%
to raise contrast, (__ scale of contrast)(more shades of __) you must do what
short scale
more shade of black and white
decrease KVP by 15% and increase MAS by 100%
what is the 15% rule
increase in KVP by 15% doubles the density
decrease in KVP by 15% will cut density in half
what mainly controls density
MAS
what is the anode heel effect
rotating anode is angled that produces varying intensity of x-rays
intensity and density decreases on anode side of film
place thinner portion of what is being xray toward this end
(example: you would place the anode end of the xray tube towards the toes and cathode end towards the ankles)
what is the inverse square law
intensity is inversely related to square of FFD
40 inch FFD is doubled to 80 in FFD, so intensity is 1/4
this means we must increase MAS by 4 times
80 inch FFD is reduced to 40 in FFD, so intensity is 4x
this means we must reduce MAS by 1/4
what makes up the intensifying screens?
why is this important
what is the intensifying screens job
fluorescent crystals
small crystals - less light - lower contrast
large crystals - more light - more contrast
increases density by intensifying xray photons
converts xray photons to visible light
what is the picture made by the useful beam
umbra
what are the blurry halo parts of the image
penumbra
how do we decrease penumbra
increase FFD
decrease OFD
small filament
small focal spot
scatter can be reduced by what 4 things
grids
air gap technique
collimators
filters
what is the proper grid ratio
12:1
what is the best way to reduce scatter
collimation
1 RAD =
1 REM
which primary radiation is majority of useful beam
bremstralung
low energy photon is absorbed by the subject creating a latent image
photoelectric effect
what chemicals are used in the developer
hydroquinone and phenidione
what converts one form of energy to another
transducer
what steps up or steps down the power
transformer
what term is used when a beam of radiation loses energy as it passes through matter
attenuation
