where do xrays fall on the electro magnetic specturm
above ultraviolet and below gamma
what are xrays similar to
visible light
the higher the frequency the ____ the wavelength, the more ______ ______ the energy has through space and matter
shorter; penetrating power
viewing a sloped surface at an angle reduces its apperant size
line focus principle
how many pulses does full-wave rectification allow
120 pulses per second
most modern, most powerful, shorter exposure time, and best generator
3 phase
what are the cathode and anode made up of
tungsten
metal deposits on inner lining
arching
process of changing alternating current to direct current
recitification
what reduces the xray machine input voltage from 110-220 vo to 10 v to prevent filament burnout
step down transformer
what controls filiment temp
step down transformer
controls length of exposure
timer switch
the peak energy of the xrays which determines quality of xray beam
kilovoltage
what controls kilovoltage
autotransformer
quality (penetrating power
kvp
what is made of molybdenum due to high melting point and poor heat conductor
focusing cup
type of anode found in dental and portable xray units
stationary
type of anode continually provides a cool surface
rotating
restricting device used to control the primary beam size
collimator
xray tubing rating expressed in
kilowatts
stationary anodes focal spot size
small
high kvp and low mas prevents
anode damage
what dound does a failed anode bearing make
grinding metal/ no noise
how far away should you be from the machine
6 feet
what increases incoming volts to 1000 of volts
step up transformer
effect of making the focal spot size appear smaller when viewed from film position due to angle of target to electron stream
heel effect
what creates a partial shadow of the imaged object
halo effect
ideal focal spot size and why
small; greater detail
1 cause of xray tube failure
cathode failure/ filament evaporation
electrical thermal rating for table top xray
40-120
what should be placed toward the cathode due to heel effect
large size
1st phase of exposure
filament heats and anode spins
NCRP
national committee on radiation protection and measurements
who defines MPD
NCRP
rule to promote radiation safety
ALARA
are we allowed to restrain and position animals according to codes
yes
RAD
radiation absorbed dose
absorbed dose measured in
grays
dose equivalent measured in
sieverts
ability to monitor amount of radiation received
dosimeter
pen shapped; charged ion chamber, can be red instantly
PIC
contains calcium fluoride and lithium fluoride that glow after exposure
thermoluminescent dosimeter
how often should PPE be radiographed
annually
“live view” of internal anatomy
fluoroscopy
what do animals drink for a fluoroscopy
barium sulfate
cells most sensitive to ionizing radiation
rapidly dividing; growth, gonad, neoplastic, metabolically active
damage done to the body that shows later in life
somatic damage
signs of somatic damage
cancer, cataracts, aplastic anemia, sterility
1 gray=
100 rad
what exposure is lethal to humans
300 rad; 3 gy
MPD
max permissable dose
100rem=
1 Sv
most common dosimeter
filmbadge
PPE lead thickness
0.5mm
intensity inversely proportional to SID
inverse square law
FFD too short =
dark
mA=4x the distance
inverse square law
what is determined by kVp
quality
what is energy related to motion called
kinetic
sante’s rule formula
(2x thickness)+ 40=kvp
what is the measure of electron current to the filament that determines how many xrays are produced
mA
how are mAs calculated
mA x time
what is time measured in
fractions of seconds
4 advantages of high mA
short exposure, decrease artifacts, exam of thick areas, decrease exposure
FFD is always
40 inches
measurable distance between 2 adjacent densities
contrast
varying degree of blackness
density
new mAs with new SID
old mAs [(new SID2)/(old SID2)]
how easily details can be seen
radiographic quality
increasing what can produce greater density
mAs, kVp, developing time, developer temp
if thickness of tissue doubles, xrays reaching film is
halved
12 mAs and 68 kVp halved=
6 mAs and 68kVp
where is best detail
200 mA and 1/10 sec
high contrast = __ kVp
low
what is high contrast used for
bone
low contrast = __ scale
long
what is high kVp used in
soft tissues
overexposed
too dark
underexposed
too light
non image forming radiation
scatter
high kVp = __ scatter
more
distance from tube to grid
grid focus
decrease intensity near edges of grid due to absorption of primary beam
grid cutoff
what is caused by misalignment of grid
grid cutoff
what grid ratio is better
high
what absorbs more scatter with more exposure
high grid ratio
lead strips are angled slightly to line up with primary beam
focused grid
focused grid that moves back and forth during exposure
bucky
variation in normal size and shape due to relation to xray source and film
geometric distortion/magnification
what is foreshortening common with
severe hip dysplasia
what do you adjust on an overpenetrated radiograph
kVp
what is used to describe image sharpness, clarity, distinctness, and perceptibility
radiographic detail
if a radiograph is overexposed with an overall black apperance but contrast is unaffected what should be done
decrease mAs
noninvasive radioactive material injected iv
scintigraphy
high definition
slow screen speed
regular most common speed
medium
high speed
fast
what part of film composition contains silver halide crystals
emulsion
what requires less exposure of xrays
screen film
large crystal film
fast
most often used film
medium
small crystal film
slow
forgiving film
wide
high contrast film
narrow
gives off green light
rare earth
gives off blue light
calcium tungstate
how often should screens be cleaned
monthly
what percentage of film exposure is due to screen light
95%
increase in film speed gives a radiograph a spotty or mottled appearance
quantum mottle
purpose of developing
convert latent image to visible
