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90 Cards in this Set
- Front
- Back
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rotor
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iron
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stator
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electromagnet
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# of filaments in average machine
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2
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fxn of bucky
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to remove grid line artifacts
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primary beam
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aka useful beam
anode |
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increase TID (tube-image distance)
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magnification decreases
detail increases |
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disc angle with the most heat
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smallest angle
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determines if exposure is tube safe
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tube rating chart
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increase in OFD (object film distance)
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magnification increases
detail decreases |
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results in the highest density
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mighest mAs to kV ratio
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spinning top test set to 1/20= how may dots?
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6, (120x1/20=6)
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spinning top test is...
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related to timing accuracy
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more penetration=
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increase kV
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max kV is determined by
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#/sequence of structures kV passes through
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generator w/ highest ripple effect
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single phase unit
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small focal spot
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greater detail and greater heat
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fxn of tube housing
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reduces leakage
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detail is greatest at...
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anode
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intensity of electrons is greatest
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cathode
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evens out x-ray
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compensatory filter
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least amount of scatter
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highest kV
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one xray at 40" and one @ 80"
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@80"= 2X distance + 1/4th the intensity (inverse square law)
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half value layer (HVL) measured in
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mm of Al
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primary filter
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hardens the beam
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primary beam radiation is
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bremsstrahlung (braking) (85% of xrays)
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penumbra is related to
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detail
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photoelectric effect
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contrast
increased density (barium swallow) |
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stator
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creates magnetic field and causes anode to spin
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if @ 80kV the film is too light
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double the mAs
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a result of outer shell electron ejection
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compton effect (A-P lumbar scatter)
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double the mAs
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increases density
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anode disc spins at
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3400 rpm
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advantage of rotating vs. stationary anode
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less radiation
less heat generated |
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increasing grid ratio....
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removes more scatter, so we increase mAs
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decreasing SID (source image distance/FFD)
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inceases magnification
decreases detail |
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1st xray for medical reasons
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mrs. roentgen's hand
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1st xray from which university
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wurzburg in
germany |
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3 reasons to use tungsten
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high melting poin
high atomic # high conductivity |
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mAs tells you
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the # of xrays created
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optimal mAs
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highest current w/ least amount of time
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allows for heat transfer from the heat sink to the disc
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molybdenum rod
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max mAs for a single exposure
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600 mAs
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do you need more mAs for an obese pt?
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increase the time & position the pt. recumbent
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how do you warm up the tube?
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take a few small exposures
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purpose of direct vs. alternating current
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rectification
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3,6 and 12 pulse machines
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CT scans
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smallest exposure time
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1/120 second or 120 pulses/s
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advantage of high frequency
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50% decrease in radiation.
decrease time, increase detail |
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advantage of small anode angle
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greater detail
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if you double the FFD you must alter the
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mAs X4 due to inverse square law
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filament
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thoriated tungston
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rotor
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iron
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fxn of focusing cup
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focus electrons
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primary xray beam created at
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anode
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increase FFD
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decrease magnification
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anode disc angle with greates heat exposed
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5 degrees of smallest
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highest contrast if mAs is the same
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the lowest possible kV
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the 15% rule is related to
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kV
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optimum kV is determined by
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sequence of structures
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generates the highest ripple
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single phase, 100%
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small focal spot
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greater detail
greater heat |
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detail of the beam is from
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anode
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longest/widest scale of contrast
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higher kV
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primary filter
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hardens the beam
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t/f the 1st nobel prize went to willie roentgen
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true!
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if the film is too dark...
if the film is too light... |
cut mAs in half
double mAs |
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how is heat created in xray?
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electron bouncing creates ions which create heat
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where is the primary filter
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between the tube and collimator
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at what kV are all xrays absorbed by the body
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40kV
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compensating filter
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eliminates free radicals (soft radiation)
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what does a filter do to a beam?
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hardens it
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fxn of HVL
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decrease strength of beam by 50%
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why are lateral ful spine films useless?
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too many differences in densities
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# of filters in full spine
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2
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the problem w/ backscatter is...
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operator exposure
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photoelectric
compton effect |
inner shell
outer shell |
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at what angle do xrays reflect at?
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45 degrees
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scatter radiation is always bad
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it decreases film quality
the rays do not go in the same direction as the central ray |
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if you cut the field of view in 1/2...
if you double the field of view... |
double the mAs
half the mAs |
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relationship b/n kV and scatter...
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as kV increases scatter increases exponentially
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how is scatter affected with obese patients
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more scatter
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w/ an obese pt...
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increase mAs, never kV
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fxn of the grid
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to absorb scatter so that primary radiation can penetrate
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fxn of bucky
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to remove gridline artifacts
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how is grid ratio measured?
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height of strip/distance between strips
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what does an increase in grid ratio do?
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less scatter and more detail w/ better contrast
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as grid ratio increases
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both mAs and kV are decreased
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who invented the grid?
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Bucky
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who invented the bucky?
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hollis
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1st diagnostic xray in the U.S.
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dr. frost took of eddy mccarthy
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