exam Flashcards
true or false: the maximum wattage a safelight can be is 10
false: max wattage is 15
what colour safelight does BLUE sensitive film require?
brown
what kind of film requires a RED safelight?
green and blue light sensitive film
how do you perform a safelight test?
take a piece of film, expose it to the light in 1/4 increments for 1 min each; keep unexposed portion covered during the intervals
what is the purpose of developer?
converts a latent image to a visible image by converting the exposed silver halide crystals to black metallic silver
true or false: in manual processing, the unexposed silver halide crystals are still sensitive to light after the developer (in rinse bath)
true
how many purposes does fixer have in the processing of a radiograph? what are they?
2 purposes;
clear away unexposed/undeveloped silver halide crystals and to harden the emulsion
how might you end up with reticulation?
if processing chemicals are at different temperatures
what are some advantages to automatic processing?
standardized quality of radiographs
fast
quick dry
saves manual labour
what steps would you follow to start our automatic processor at seneca?
- close wash drain valve - developer and fixer valves should also be closed
- open water supply tap
- close processor cover and feed tray from teepee position
- turn on power breaker
- press the RUN button
- wait for the READY lamp to light up (~20min)
how would you turn off the automatic processor at seneca?
- turn off power breaker
- close water supply
- open wash drain valve
- open feed tray cover and processor cover, place in teepee position
what are the main differences between manual and automatic processing?
automatic does the same job at: higher temp with special chemicals no rinse between developer and fixer (squeegee) motor driven
what should be on an x-ray label?
name date address of hospital practice/vet name paitient ID (owner, sex, age, breed) log number
what is ionizing radiation?
radiation that has enough energy to remove tightly bound electrons from atoms (making them into ions)
how many types of ionizing radiation are there? what are they?
4; alpha particles, beta particles, gamma rays and neutron particles
what is the most dangerous form of ionizing radiation?
gamma rays
what is the danger associated with ionizing radiation?
when ionized, cell function is disrupted - can cause somatic or genetic damage
what kind of crystal is contained in thermoluminescent dosimeters?
lithium crystal
how does a dosimeter work?
crystal is heated, stored energy gets released as light and is measured by device - shows accumulated radiation exposure
what PPE is required when restraining for radiographs?
gloves
apron
thyroid shield
protective glasses
what is the required thickness of lead in protective gear?
0.5mm
what is another name for secondary radiation?
scatter
what is an x-ray?
form of electromagnetic radiation
true or false: x-rays have greater energy and longer wavelength than visible light
false: x-rays have greater energy and SHORTER wavelength than visible light
as wavelength ____ energy ______
decreases, increases
true or false: a shorter wavelength contains more penetrating power than a long wavelength
true
how are x-rays produced?
electrons are emitted from the cathode, accelerate toward the anode where they collide with atoms- if the electron gets close to a nucleus it loses energy and emits a photon (x-ray)
what determines the quality of a radiograph? (how well you can see the image)
kVp - penetrating power
what determines the quantity of x-rays available for the radiograph?
mAs - the number of electrons that will be available to be converted to x-rays are produced at the cathode
what factors other than electrons affect the quantity of x-rays produced?
exposure time
mA x time
mAs
as mAs increases, the quantity of x-ray beams should also ____
increase
what does kVp stand for?
kilovoltage potential or kilovoltage peak
as kVp is increased, electrons in the tube head move _______
faster
would higher kVp settings mean x-rays with longer or shorter wavelength?
shorter
what is sante’s rule used for ?
estimating kVp setting
how do you calculate kVp using sante’s rule?
thickness in cm x 2 add 40 (SID in inches)
what is SID?
source image distance: distance between focal spot and film
how does SID affect images?
affects the intensity
as SID ____ image intensity ____
decreases, increases
explain inverse square law as it pertains to SID
as SID increases, intensity decreases … if SID is two times further, the image will have 1/4 the intensity
aside from intensity, name one other factor affected by a change in SID
detail
how will you know a film is underexposed?
film will seem too light
overexposed film looks like what?
too dark
as exposure is increased, the film will become _____
more black
how can you identify a penetration problem in your radiograph? how would you alter settings to fix?
if you only see indistinct/imperceptible silhouettes of organs; increase kVp 10-15% to fix
how can you identify a density problem? how would you alter settings to fix?
organs are visible, but you can’t see them well - film was penetrated enough, it’s just too light; double mAs to fix
if bones are gray what happened to the radiograph? how would you alter settings to fix?
image is over penetrated; decrease kVp 10-15% to fix
if bones look white, but soft tissue looks too dark, what is the problem? how would you alter settings to fix?
too many x-ray beams hit the film, causing image to be darker (density problem); decrease mAs by half to fix
true or false: we want high contrast for soft tissue
false; soft tissue should always have low contrast
what does low contrast look like?
many shades of gray
what kind of contrast is best for bone?
high contrast
true or false: a radiograph with high contrast will make a bone look distinct from its surroundings
true
if the background is quite light, what setting might be incorrect?
mAs; if background is light it is too low, should double
what are the four basic criteria for patient positioning?
- welfare of patient
- restraint/immboilization of patient
- minimal trauma to the area of interest
- last exposure to assistants
abdomen: take on inspiration or expiration
expiration
thorax: take on inspiration or expiration
inspiration
where do you measure for a thoracic radiograph?
caudal border of scapula
true or false: when radiographing the heart we should take VD view
false: heart should be taken with DV
true or false: lungs should be radiographed in VD view
true
where do you center the beam for a lateral thoracic radiograph?
5-6th rib, caudal border of scapula
where do you center the beam for DV/VD thoracic radiograph?
over caudal border of scapula
what are the peripheral borders for thoracic radiographs?
scapulohumeral articulation to L1
should thoracic radiographs be taken on inspiration or expiration?
inspiration
what are some concerns we might have when taking a DV radiograph?
motion
hip dysplasia (cannot be square)
deep chested animals
trauma
what does it mean to take a lateral decubitus view radiograph?
lateral decubitus takes a VD radiograph while the animal is in lateral recumbency; the beam hits the patient horizontally instead of vertically
how do you identify if a thoracic radiograph was taken on inspiration or expiration?
lateral: size of heart, sternal contact, distance from apex to diaphragm
VD/DV: size of heart, distance from apex to diaphragm
how would you differentiate a DV from V thoracic?
DV: diaphragm is v shaped, vertebrae appear more magnified, heart looks like lopsided egg
what is the difference in the appearance of the diaphragm on a VD thoracic vs. DV?
VD: diaphragm looks like a dome
DV: diaphragm looks more pointed
how would you differentiate between a right lateral thoracic and a left lateral thoracic with no marker?
right: heart looks rounded
left: heart looks more boxy
where would you measure for an abdominal radiograph?
thoracolumbar junction/caudal aspect of 13th rib
where would you center the beam for a VD abdominal radiograph?
over caudal aspect of 13th rib (2-3 fingerbreadths caudal for feline)
what should you include in a VD abdominal view?
T9 to femoral head (may not fit in one view for larger patients)
should a VD abdominal radiograph be taken on max inspiration or expiration?
expiration
what might be some concerns with performing a VD abdominal x-ray?
trauma
bloat
emaciation
obesity
where would you center the beam for a lateral abdominal radiograph?
over caudal aspect of 13th rib
what are the peripheral borders for a lateral abdomen?
caudal aspect of T7 to femoral head
how might your exposure time be altered for an obese cat vs. an emaciated cat?
obese: requires increased exposure
emaciated: should have decreased exposure
how would you define density and contrast in common terms?
density: the degree of blackness
contrast: difference between the adjacent densities
what factors will make the film more black when increased?
mAs
kVp
developing time
developing temperature
will a thinner body part (i.e. radius/ulna) be more or less dense in comparison to a thicker one?
more dense; will show up darker
as you ____ subject density you will have ____ film density
increase, decreased
define subject contrast
difference in density and mass between 2 adjacent anatomic structures
define radiographic contrast
density difference between 2 adjacent areas on a radiograph
high contrast is associated with ____ kVp
low
explain low contrast
many different grays with small differences in density; it takes a long time to get from black to white
true or false: if you set the machine to a fairly high kVp setting, chances are your radiograph is going to turn out with high contrast
false; as kVp settings increase, the image will have lower contrast
when taking and developing diagnostic radiographs, is it good to have extreme differences in contrast?
no; should have a good range of blacks, whites and grays for a good quality image
what is the principle control of contrast in radiography?
kVp
if you develop an image and are not satisfied with the contrast, what setting will you need to alter?
kVp
true or false: as it pertains to contrast, higher penetration will result in lower contrast
true
does kVp only affect the contrast of an image?
no, kVp affects both contrast and density of an image
what other results could you see from increasing the kVp setting?
increased scatter and/or grayness - this is also a reason for lower contrast with higher kVp
what are three reasons scatter may occur?
thick patient
high kVp
increased field size
what is the purpose of using a grid? when would we use it?
grid absorbs scatter radiation so the primary beam can reach the film better; used when patient measures thicker than 10cm
what are the peripheral borders for radiographing long bones?
include joints distal and proximal
what are the peripheral borders for radiographing joints?
include 1/3 of limbs distal and proximal
what views should be taken for a scapula?
lateral
CdCr
what views should be taken for a shoulder?
lateral
CdCr
what views should be taken for a humerus?
lateral
CdCr
(CrCd)
what views should be taken for an elbow?
lateral (flexed and extended)
CrCd
what views should be taken fora radius/ulna?
lateral
CrCd
what views should be taken for a carpus?
lateral
dorsopalmar
obliques (?)
what views should be taken for metacarpals/phalanges?
lateral
dorsopalmar
obliques (?)
what views should be taken for a pelvis?
lateral
VD
frog leg (trauma)
what views should be taken for femur?
lateral
CrCd
what views should be taken for a stifle?
lateral (flexed and extended)
CrCd
CdCr
what views should be taken for a tarsus?
lateral
PD
DP (?)
what views should be taken for a metatarsus/phalanges?
lateral
PD/DP
where would you measure for a limb radiograph?
thickest area
where would you center the beam for a long bone?
mid-diaphysis
where would you center the beam or a joint?
at the articulation
why is it important to extend the neck dorsally when taking a lateral shoulder radiograph?
to keep the trachea and possible ET tube dorsal to the scapulohumeral articulation (otherwise will be superimposed)
where would you measure for a pelvis radiograph?
level of greater trochanter (over acetabulum)
where would you center the beam for a lateral pelvis?
over greater femoral trochanter
why might you need to take a lateral oblique view for pelvis?
if each femur needs to be seen, or hip luxation
when would we use a VD frog leg position?
pelvic stress/trauma
true or false: on a true lateral pelvis the affected and contralateral limbs are not superimposed
false; for true lateral both hind limbs should be superimposed
what should be included in view for a lateral oblique pelvis?
entire pelvis, plus femur and patellae
what should be included in field of view for VD frog leg pelvis?
entire pelvis, at least 1/2 of femurs
what must be included for VD extended view (hip dysplasia)?
entire pelvis, femurs and stifles
when submitting radiographs for hip dysplasia to OFA or Penn Hip, is it okay for there to be rotation of anatomy?
no, the image must be symmetrical
what does normal femoral anatomy look like?
130 degree angle of femoral neck cranial 1/3 joint space of equal width at least 1/2 femoral head in acetabulum rounded/smooth femoral heads smooth femoral neck
what 3 views are required for Penn HIP?
standard extended view
compression view
distraction view
what would you include for a lateral view of the femur?
hip joint, femur and stifle joint
in general, what position will the animal be lying in for distal hind limb radiographs?
ventral recumbency (on their stomach)
what are some examples of dark artifacts?
static inverted grid light leak scratches trapped air (towel)
what are some examples of white artifacts?
wet matted hair sandbags spilt fixer flea collar lead marker damaged intensifying screens
true or false: penumbra is caused by movement of the animal
true
what is penumbra?
a lack of detail, or geometric unsharpness
foreshortening and elongation are forms of what? what causes them?
geometric distortion/magnification
foreshortening: subject not parallel
elongation: tube head not parallel
what is the purpose of a grid?
to prevent scatter radiation from reaching the film; absorbs them to produce a better quality image
as scatter increases, contrast ____
decreases
what is a grid composed of?
lead strips
how do grids absorb scatter radiation? are they 100% effective?
the direction of the beams from scatter radiation do not align with the spaces between absorbing strips - the primary beam does align, so it can get through to the film
no grid will be 100% effective at preventing scatter from hitting the film
define grid focus
distance from the focal spot to the grid
define grid cut off
a progressive decrease in transmitted x-ray intensity caused by absorption of primary x-rays by the grid lines
when does grid cut off happen?
when the grid is not used properly - grid lines will absorb more x-rays than they should
three example causes of grid cut off
- improper centering under tube
- tilting the grid
- tilting the tube
define grid efficiency
how well a grid can absorb non-image forming radiation in the production of a quality radiograph
what factors contribute to grid efficiency?
grid ratio height
lines/cm thickness (of lead)
define grid ratio
relation of the height of the lead strips to the distance between them (i.e. 10:1)
true or false: the higher the grid ratio, the lower the efficiency of the grid
false; the higher the grid ratio, the higher the efficiency
what are some possible setbacks to using a higher grid ratio?
requires higher quantity of x-rays/higher exposure factors
grid cutoff will be more noticeable
how do the number of lines per cm in the grid affect its efficiency?
grid with more lines per cm area have better efficiency to absorb scatter radiation; there is less space between them therefore less will get through to the film
what is a grid pattern?
the orientation of lead strips in longitudinal axis
how many types of linear grid are there?
three
what type of grid do we use at seneca?
focused grid
how is a focused grid oriented?
lead strips are angled
focused on central point of grid
strips radiate from the centre and have a greater incline to the edge
what is the purpose of intensifying screens?
to intensify the effect of x-rays during exposure to film
what is an intensifying screen composed of? how does it work?
a sheet of crystals called phosphors; when exposed to x-ray radiation they are excited and emit fluorescent light
true or false: most of the latent image is created from direct exposure of x-rays to film
false: only about 5% of the latent image is created by direct contact from the beam - 95% is from the glowing crystals
there are multiple layers within the intensifying screen - what are they?
phosphor layer
reflective layer
what happens in the phosphor layer of the intensifying screen?
x-ray radiation hits the phosphor crystals and they fluoresce
what happens in the reflective layer of the intensifying screen?
as light is emitted from the crystals, it bounces off this layer and reflects onto the film
what is the primary purpose of intensifying screens?
to reduce the amount of radiation exposure required to produce a diagnostic radiograph
as phosphor efficiency _____ absorption _____
increases, increases
an efficient crystal can take one x-ray beam and turn it into _____ of beams of visible light
hundreds
true or false: light photons are more readily absorbed by film than x-rays
true
in terms of intensifying screens, what do we mean by “conversion”?
the conversion of x-rays to visible light (in the cassette)
what is afterglow?
crystals still emitting light after radiation exposure has stopped
a good quality intensity screen should have what factors for absorption, conversion and afterglow
high absorption
high conversion
low afterglow
true or false: lanthanide rare earth crystals are less efficient than calcium tungstate
false: lanthanide crystals are more efficient, and considered newer technology
do calcium tungstate crystals require higher or lower exposure factors?
higher
what spectrum do calcium tungstate emit in?
blue region
what spectrum do lanthanide crystals emit in?
green spectrum
true or false: lanthanide crystals are 4x faster than calcium tungstate
true
what is the major benefit to using rare earth crystals?
they require lower mAs
crystal size governs what in the intensifying screen?
screen speed
true or false: as speed increases, grain will also increase
true
what is the most common size crystal used in practice? why?
medium: good resolution, medium grain, midrange exposure factors
other than crystal size, what affects the speed of the intensifying screens?
phosphor layer thickness
reflective layer efficiency
true or false: seeing small “horse heads” between vertebrae is a good thing
true
what are the two normal views for spine
VD
lateral
what two views would you perform if there were spinal trauma?
lateral
lateral decubitis
how many vertebrae should you include in one view?
usually a maximum of 5
where would you measure for a spinal radiograph?
thickest part
where would you center the beam for a spinal radiograph?
mid vertebral region (remember to only include 5-6)
how should you decipher peripheral borders for spinal radiographs?
always include 1 vertebrae cranial and 1 caudal other than main part
what view is performed for cervical spine?
VD
what are 3 lateral views that can be performed for spinal radiographs?
extended
flexed
hyperextended
what views can be performed for thoracic spinal radiographs?
VD
lateral
what views can be performed for lumbar spine?
VD
lateral
what views can be performed for sacrum?
VD
lateral
what views can be performed for caudal (tail) vertebrae?
VD
lateral
