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Imaging Lecture 3

Terms

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What does OFA stand for?
Orthopedic Foundation for Animals
OFA reviews and evaluates films for evidence of what?
Hip dysplasia
What xray view is sent to OFA?
V/D Pelvic
How many DVMs evaluate a film for OFA? How many must agree?
Three evaluate, 2 must agree
If the hip joints look normal, what is issued by the OFA?
registry #
How long does an OFA evaluation take?
Owner and vet are notified w/i 3-6 weeks.
What is the age requirement for OFA eval?
min 2 years
What is the required restraint for an OFA film?
sedated/anesthetized
What 7 things need to be on the image label of an OFA film?
hospital/vet name, date, owner name, breed, age, AKC reg #, perm id # (tattoo or microchip)
What must be included in view for OFA film?
wings of illium through stifle
Describe the positioning for an OFA film
dorsal recumbency w/ V-trough or sandbags, rear limbs flexed into a frog position, tarsals grasped and stifles rotated medially, when they are 1-2" from eachother, the limbs are extended caudally until parallel to the cassette or resistance is met
What Technique for imaging hips was developed in 1980 at the U of PA?
PennHip
The Penn Hip method requires three views - what are they?
standard OFA, compression view w/ neutral position, distraction view in neutral position
In absence of dz, _______ is the single most valuable item in predicting hip dysplasia
laxity
What is the benefit of the PennHip method over standard extended view?
Has been shown to give a a more dependable, repeatable, and reliable view of a dog's passive hip laxity
What is it called when the fit of the hip joint is loose?
hip dysplasia
How is hip dysplasia seen on x-ray?
separation of the head of femur and acetabulum
How does the body react to hip dysplasia?
causes change in bone and articular cartilage
what is the end result of the changes caused by hip dysplasia?
Osteoarthritis and degenerative joint dz
Do radiographic findings always correlate w/ clinical signs?
No, dog with no clinical signs may have gross changes on xray, and a dog with no signs on x-ray may be in severe pain or crippled
Is hip dysplasia hereditary?
Yes
What is the only positive dx of hip dysplasia?
radiography
What kind of film is used in oral radiography?
non screen as it provides the most detail - bite wing film is the same as in humans
What restraint method is used in oral radiography?
chemical
When positioning for oral radiography, you want the _____ ______ of both the tooth and the film perpendicular to the x-ray beam
long axis
A decreased ______ is recommended for oral radiography exposure
SID
What three radiographic changes are associated with periodontal dz?
loss of alveolar bone, widening of radiolucent space due to loosening of periodontal ligament, and periapical bone loss
In addition to separate technique charts for each machine, what other four things require separate charts?
scree/non-screen film, grid/no-grid, different species (avian), different anatomical parts
What four variables need to be standardized when making a technique chart?
processing, SID, grid type, film & screen type
Typical technique charts factor in a grid for what three anatomical parts?
Abdomen, thorax, and pelvis/spine
Typical technique charts do not factor in a grid for what two things?
extremities/skull and avian/exotics
What features make for a good dog model to use when creating a technique chart?
Adult, avg. weight, moderate muscling, and a hair coat that is clean and med-short in length
If the anatomical part is over ____ in thickness, a grid should be used
10cm
What is standard SID used when creating a technique chart?
40"
What is Sante's rule used to calculate?
KvP
Sante's equation
2x tissue thickness (cm) + SID + grid factor = KvP
When creating technique chart, what is the MA set at?
Highest possible
What is the grid factor if the grid ratio is 5:1?
6-8 KvP
What is the grid factor if the grid ratio is 8:1?
8-10 KvP
What is the grid factor if the grid ratio is 12:1?
10-15 KvP
What is the grid factor if the grid ratio is 16:1?
20 KvP
What do you do if the film is too dark when creating a technique chart?
decrease MAS by 30-50%
decrease KvP by 10-15%
What do you do if the film is too light when creating a technique chart?
Increase MAS by 30-50%
Increase KvP by 30-50%
What is the formula to calculate the time when creating a technique chart? What is done if a grid is used?
Time = MAS/MA
Time is doubled if using a grid
When creating a techniques chart, what is done to the KvP in relation to every cm of thickness?
Increased/decreased proportionately by 2 KvP

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