Radio LA I
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A radiographic image is formed by differential ___ of parts of the imaging system to radiation as a result of differential ____ by parts of the patient.
what are 3 options for when radiation comes in contact with matter?
transmitted, absorbed, scattered
What is the term for the amount of radiation produced by the x-ray tube?
What is the term for the amount of radiation to which patients, radiographers and public are exposed?
what is the term for amount of radiation which reaches a photographic film or digital imaging device?
What 4 things does aborption of radiation by body tissues depend on?
- atomic number
- physical density
- thickness of tissue
- energy of beam
The atomic number and specific gravity of ALL soft tissue structures except ___ approximate that of water
Air, fat, water, bone: which has highest anatomic number and specific gravity?
bone (14, 1.8)
air, fat, water, bone: which has lowest anatomic number? lowest specific gravity?
- anatomic: fat (5.9)
- SG: air (0.001)
air, fat, water, bone: which is most radiolucent? highly opaque?
- air= radiolucent
- bone = opaque
Which is more opaque, fat or water?
water (moderately opaque)
Does scattered radiation contribute to formation of image?
How can scatter be reduced?
- FILTRATION of beam
- efficient COLLUMATION
- minimize EXPOSURE factors by using appropriate systems
- use a GRID
What is main disadvantage of using a grid?
increased exposure factors required
What is term used to indicate image is taken of animal standing and horizontal beam used?
What is term used to indicate image taken to simulate weight bearing, demonstrating articulate instability?
What does inverse square law refer to?
that distance is best way to protect from unwanted radiation
What is a negative photographic image recorded on film or digitally?
what is usually in the light proof case where the film is placed to take a radiograph?
cassette w/ light intensifying screen
What are two types of digital radiography?
- computed radiography
- direct digital radiography
What kind of image is generated in photographic radiography and computed radiography?
What replaces the cassette for direct digital radiography? What is a disadvantage of this system in equine rads?
- receptor plate
- requires a cord btwn sensor and processor
How should foot be prepared for rads?
- remove all mud and shoes unless contraindicated, pack frog w/play-doh
- consider sedation
If the clinician asked you to take a weight bearing, "high coronary" image to evaluate the navicular bone or P3, which projection would you take?
D65Pr-PDiO (dorsal 65 degree proximal, plantar distal oblique)
What projection is used for "upright pedal"?
What is a skyline view for the navicular?
PPr-PDiO (Palmar proximal - palmar distal oblique)
For projections of the foot (DP or LM), where should beam center?
on coronary band (can put foot on block)
For evaluating the distal phalanx, do you want a low or high exposure to evaluate the bones? What about for the joints?
How do you describe a normal P3 solar margin?
should be smooth with 5-9 vascular channels around border
What angle should P3 be in relation to weight bearing hoof wall?
If you draw a perpendicular line from the center of P2 to bearing surface, where should it pass?
through middle third of weight bearing surface
What are two normal variants to be aware of when evaluating P3?
- ossification of collateral cartilages
- separate ossification center at extensor process
What are some rad findings for osteitis?
- localized defect : sepsis
- resorption of bone on palmar process
- generalized marginal irregularity: incr. # vascular channels
What is the crena?
normal flattened segment at toe
What is a rad sign of laminitis?
distal rotation of P3
What is spur formation on the navicular bone?
ossification of collateral ligaments (clinical significance?)
What is another term for synovial fossae?
- vascular channels
- nutrient foramina
what are rad signs of navicular disease?
- incr. synovial fossa (>7) on distal border
- synovial fossa on sloping borders
- altered shape of fossa (lollipop)
- erosion of flexor cortex
- sclerosis of medullary bone
What condition does the horse have with true ring bone?
What is bone proliferation from periosteum damage directly (ie kicked)?
What is boney proliferation of periosteum damaged by avulsion from soft tissue structures like ligaments/joint capsule pulling away from bone?
What view allows best visualization of saggital ridge of MCIII?
flexed lateral view
when does distal MCIII physis close? What about proximal P1? and proximal P2?
- distal MC3: ~9mo
- proxP1: ~12 mo
- proxP2: ~9mo
Do MC2/4 have proximal physis?
Where does angular limb deformity most commonly originate in the foal?
distal radius (occasionally asymm. devl of carpal bones)
A true cranio-caudal view of the shoulder is not feasible in the horse; so what view is taken?
cranio-medial - caudo-lateral (cassette against thoracic wall behind triceps)
What are radiographic signs of spavin (tarsal degenerative joint disease)?
- loss of subchondral bone
- osteophyte "lipping" at joint margins
- peri-articular new bone formation
Where is spavic most commly noted?
dorso-medial aspect of distal intertarsal joint
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