Ch. 1 & 11 Flashcards
electromagnetic energy is also known as what
radiation
output of radiographic unit’s radiation measurement in air
coulomb/kilogram (c/kg)
we use these instead of parallel grids to prevent grid cutoff due to beam divergence
focused grids
grid that can be used on both 40” and 72” SID
dual focused grid
what do filters do
filter out low energy photons which decreases patient dose
x-ray tubes operated above 70 kVp are required a filtration of what
at least 2.5 mm aluminum
particulate matter capable of ionizing an atom
alpha and beta particles
radiation that is capable of removing an orbital electron from one of the subjects atom
ionizing radiation
what are all the names for kVp
strength, penetration, quality, potential difference, electric potential
who initially brought to light the dangers of x-ray and who else was the first casualty
Thomas Edison; Clarence Dally
what does CT stand for
computed tomography
what is penumbra
blurring of the edges (unsharpness)
direct square law is also called
maintenance law
what is the speed of light
3x10^8 m/s
how is the magnification factor (MF) calculated
SID/SOD=MF
to maintain optimal exposure while changing the SID you use
direct square law/maintenance law
increasing kVp does what to patient dose
decreases patient dose by increasing transmission and decreasing absoption
decreasing collimation does what to scatter and contrast
increases scatter and lowers contrast
using a grid does what to contrast
increases contrast by eliminating scatter
the head and neck of the anode are made of what
molybdenum
what do you do if your image is under exposed and under penetrated
increase kVp by 15%
what is the negative side of the tube head called
cathode
insufficient mAs will result in what
increased quantum noise (grainy image)
what does a grainy image indicate
not enough mAs
40” is equivalent to how many cm
100cm
72” is equivalent to how many cm
180cm
as SID increases what happens to spatial resolution and magnification
spatial resolution increases and magnification decreases
tube head assembly includes what
x-ray tube, collimator, stand/overhead
a minimum of how much change in kVp is needed in order to see it with your human eyes
10% change
the higher the SNR
the better the image/spatial resolution
when do we use a grid
body part is over 10 cm thick
what does scatter do to an image
fogs the image, decreases subject contrast
a minimum of how much change in mAs is needed in order to see it with your eyes
30% change
kVp is the main controller of what in production of the x-ray
subject contrast
what does radiopaque mean
stops/absorbs x-rays
as SID decreases what happens to spatial resolution and magnification
spatial resolution decreases and magnification increases
as OID increases what happens to spatial resolution, magnification, and contrast
spatial resolution decreases, magnification increases, and contrast increases
only way to get rid of scatter
use a grid
mAs controls what
number of photons - receptor exposure
what is a “noisy image” called/known as
quantum mottle
the only way to fix a grainy image
retake with more mAs
increasing kVp will do what to scatter and contrast
increase scatter, decrease subject contrast
what is it called when you can alter the factors kVp, mA and exposure time (s) to get the same image/dose
reciprocity law
we get an approximate dose of how much natural occurring radiation
3 mSv/yearly
largest natural source of radiation; radioactive gas produced by the decay of uranium; all earth based materials have it within them
radon
who discovered x-rays and when
Wilhelm Roentgen, November 8, 1895
measures radioactive material
Becquerel (Bq)
what side is usually on the patients head side, or our left side
anode (positive side)
visibility of detail
contrast resolution
what controls contrast resolution
use of grids
used to measure occupational dose (dose equivalent), also measures effective dose - exam based area (eyes)
sievert (Sv)
if you want tokVp see more bone what do you do
increase contrast by decreasing kVp
unit of absorbed dose, allover dose, dose in patient
gray (Gy)
using < 100 mA; small filament; small focal spot, will result in
small penumbra/good spatial resolution
what the body takes in and absorbs inside the body
dose
what is the positive side of the x-ray tube head called
anode
what do you do if you have an over penetrated and over exposed image
lower kVp by 15%
describes photons losing intensity as they travel through matter
attentuation
what mA is used for larger body parts - chest, hips, abdomen
300 mA and above
the chicken scratches on bone are called what
trabecular patterns
what do you do to maintain exposure while decreasing dose
increase kVp by 15% while decreasing mAs by half
where are x-rays made
actual focal spot on the anode
main controller for spatial resolution
focal spot size (FSS)
what does radiolucent mean
x-rays travel through it
what do you do for an underexposed image
double mAs
what do you do for an overexposed image
half the mAs
using >300 mA; large filament; large focal spot, will result in what
large penumbra, bad spatial resolution
the anode consists of what
anode target and induction motor
if you want more grays on your image you will want
low subject contrast, high kVp
detail and making of detail
spatial resolution
main controller for spatial resolution
focal spot size (FSS); OID and SID influence it
mA comes from what transformer
step-down transformer
what does ALARA stand for
As Low As Reasonably Achievable
the filament in the cathode is made of what
thoriated tungsten
kVp is secondary controller of what
receptor exposure (RE)
what material is sometimes added to tungsten on the target plate to increase thermal capacity and tensile strength
Rhenium
what does increasing the collimation do
decreases the light field
what does decreasing collimation do
increases the light field
influences of spatial resolution
OID and SID
the relationship between distance and x-ray beam intensity is best described by what
inverse square law
what mA is used for extremeties
100 and below
where are x-rays made
actual focal spot on the anode
describes photons being totally stopped in the body
absorption
50% of the population has this type of body habitus
sthenic (average)
the intensity a photon loses in the body as it travels through the body; energy given off
kerma
to maintain exposure when shooting a thicker part what must you do
increase mAs
increasing collimation will do what to scatter and contrast
decrease scatter; increase contrast, but require more mAs
describes the boiling off of electrons at the filament
thermionic emission
spatial resolution is also what
detail
how many more electrons are boiled off the large filament
4x
what does SNR stand for
signal to noise ratio
what is the range of kVp we use
60-120 kVp
how far can you be off with a grid before it effects your image
3-5 degrees
for every change of what in part thickness must the radiographer alter mAs by factor of 2
every 4-5 cm
particulate and electromagnetic radiation emitted by sun and stars
cosmic radiation
radiation naturally within us as metabolites, mainly potassium-40
internally deposited radionuclides
relationship between matter and energy
E=MC^2
glass envelope is usually made of what
borosilicate glass
photon losing intensity as it travels through air
air kerma
already on the Earth, deposits uranium, thorium, and other radionuclides on the planet
terrestrial
very slender body habitus
asthenic
what percent of population is asthenic
10%
a more slender, taller build is known as
hyposthenic
what percent of the population is hyposthenic
35%
a larger, stocky build
hypersthenic
what percent of the population is hypersthenic
5%
