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