Imaging Lecture 3
Terms
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copy deck
- 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