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89 Cards in this Set
- Front
- Back
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What radiographic views are important in the equine limb?
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Multiple views are always made
Oblique views are critical |
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How are oblique views named?
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By the direction of the x-ray beam.
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What is considered to be the most important radiographic view seen in the horse?
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Dorsomedial Palmarolateral Oblique
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In the horse, which is more common osteochondritis of the front or rear limb?
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Rear
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In what 4 areas does osteochondritis occur in the front limb of the horse?
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scapula
distal radius Metacarpal 3 distal Phalynx |
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What is the radiographic appearance of osteochondritis in the distal phalynx of a horse?
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cyst-like lesion
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The origin of an osteochondritic lesion in the dital phalynx of a horse can be what?
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developmental
Traumatic |
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Rear limb osteochondritis occurs primarily in which structures in the horse?
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Stifle & tarsus
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Osteochondritis of the equine stifle is commonly located where?
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Lateral trochlear ridge
Medial femoral condyle |
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Where are the 2 least common locations of osteochondritis in the rear limb of the horse?
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Lateral femoral condyle
Proximal tibia |
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Which view would be the best to see osteochondritis of the cranial distal intermediate ridge of the tibia?
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DMPLO
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What is the most common location for osteochondritis in the talus of the horse?
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Lateral trocheal ridge
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Equine navicular syndrome can cause lameness and heel pain. What % of cases show no radiographic abnormality?
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50%
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WHat views are used to demonstrate the equine navicular bone?
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Lateromedial
65 degree dorsoproximal-palmarodistal Skyline |
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What are the radiographic signs of navicular disease?
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Proximal border: enthesophytes on extremities (spurs)
Distal border: synovial invaginations (fenestrations) Small chip Frx. (uncommon) |
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In the navicular view of the Flexor Cortical Border, you may also see cortical erosions and mineralizations of what structure?
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DDF tendon
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WHat do you look for in the medullary cavity of the navicular bone?
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Radiolucent cyst
sclerosis |
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What are 3 common diseases of Foals?
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Angular Limb Deformity
Osteomyelitis Septic Arthritis |
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Angular limb deformities in foals are most common in which area?
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Carpus-valgus
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In what other areas can angular limb deformity occur?
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fetlock (front or rear)
Hock |
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What disease usually occurs along with septic arthritis?
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Osteomyelitis
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When do septic arthritis and osteomyelitis tend to occur?
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Few days to a few weeks of age, often affects multiple bones or joints.
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How are radiographic views named?
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In the direction in which the x-ray beam travels from the tube through the patient to the film.
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Are x-rays a wave or a particle?
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Both (photon)
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An x-ray tube anode is made of what metal?
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Tungsten
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What 2 primary interactions occur in the anode to create x-rays?
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Collision interactions (characteristic)
Radiative interactions (braking) |
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The cathode is the source for what, in the production of x-rays?
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Electrons
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What does an x-ray machine consist of?
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two electrical circuits, plus a transformer and a rectifier.
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Which circuit controls the current to the cathode filament?
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Low voltage circuit
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What does the high voltage circuit control?
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It controls the electrical potential difference between the cathode and the anode and is measured in kilovolts (kV).
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The potential difference between the anode and cathode is measured in what units/
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Kilovolts (kV)
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What are the 3 main controls on an x-ray unit?
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kVp
mA Timer |
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How is an x-ray exposure determined?
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By setting the kVp and the mAs controls on the machine
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What does the kVp control do on the x-ray machine?
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It sets the maximum possible energy of the x-ray beam and controls the penetration power of the x-ray beam.
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What does the mA control do on the x-ray machine?
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It controls the heat of the cathode filament and the number of x-rays produced.
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What does the Timer control do on the x-ray machine?
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It controls the length of the exposure
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What are the 3 basic matter-radiation interactions that can occur when an x-ray photon enters a patient?
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Coherent scattering
Photoelectric interactions Compton interactions |
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What happens to the photon during coherent scatter?
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The photon enters the patient, is not absorbed then changes direction with no loss of energy.
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What is a photoelectric interaction?
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It is primarily responsible for x-ray image formation.
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How does photoelectric interaction interact with the patient?
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The photon that enters the patient is totally absorbed, it strikes & ejects an electron completely absorbing the energy and the ejected electron. The outer shell electron falls into the vacated shell and releases characteristic photon (low energy, quickly absorbed)
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Photoelectric absorption is directly proportional to what?
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The cube of the atomic number of the absorber.
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Photoelectric absorption is inversely proportional to what?
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The cube of the energy of the photon.
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What is important about photoelectric interactions?
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Responsible for tissue differences on the image.
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Which interaction is the primary source of scattered radiation?
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Compton interactions
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WHat happens in a Compton interaction?
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The incoming photon ejects an outer shell electron and continues with a slight loss in energy, possibly reaching the x-ray film. The ejected electron is absorbed.
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Compton interactions are proportional to what?
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Independent of the atomic number of the absorber (patient) and decreases as the energy of the photon increases.
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What is the effect of Compton scatter on image quality?
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Decreases image contrast and increases more potential exposure to personnel.
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In general, when the x-ray beam enters the patient what 3 things can occur?
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The x-ray passes through unchanged to reach the film.
Photoelectric absorption occurs. Compton scatter occurs within the patient, some of which reaches the film. |
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The amount of blackness on a film is directly realted to what?
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Amount of metallic silver remaining in the emulsion, which directly related to the number of x-rays reaching the film.
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The number of x-rays produced during the exposure is related to what two factors?
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mA (heat of the cathode filament)
Length of the exposure (seconds) |
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WHat factors control the energy of the beam?
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kVp
The number of x-rays, the more x-rays that reach the film, the higher the energies used. |
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What is Focal Film Distance?
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The distance from the source of the x-ray tube to the film.
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What gives better image detail, a long or short FFD?
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A long FFD
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What is the inverse square law?
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The intensity of x-ray beam is inversely related to the square of the distance from the source.
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According to the inverse square law, if you double your distance of the x-ray source (increase FFD), what happens to the intensity of the beam?
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Reduced to 1/4 it's original.
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If you change the FFD, what must you do?
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Adjust the exposure factors accordingly.
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What FFD is used in vet med?
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100 cm (40 inches)
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Which image quality component is key to quality?
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Image detail
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What is the definition of contrast?
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The difference between the most white and the most black.
High = black Low = white |
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What type of contrast and Kvp (high/low) would be best for bone, abdomen and thorax?
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Bone- High contrast w/ Low Kvp
Abdomen- Low contrast w/ High Kvp Thorax- Low contrast w/ High Kvp |
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What is the definition of detail?
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How sharp the edges (margins) are.
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What is the definition of distortion?
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Out of the normal shape or position.
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What is focal film distance?
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It compromises between long (better detail more exposure) and short (poor detail but less exposure)
100 cm generally accepted standard. |
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How can motion be minimized or eliminated?
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Use the shortest exposure time available.
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What exposure factor would give you the shortest exposure, a high mA or low mA?
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High mA
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Which type of film would have better detail, a fast or slow film speed?
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Slow film speed
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How can film have different speeds?
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Crystal size
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What do you call the portion of the anode that is bombarded with electrons to create x-rays?
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Focal spot
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Does focal spot size have an effect on image detail?
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Yes, smaller is better.
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The distance between the patient and the film is called what?
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Object film distance (OFD)
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What is the rule of thumb for OFD?
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Have the patient as close to the film as possible.
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What does increasing object film distance do to image distortion?
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it increases it causing magnification and image blurring.
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What 3 things cause distortion?
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Increased patient to film distance
Object not parallel to the beam. X-ray beam not centered over the area of interest. |
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What happens to the x-ray when the object is not parallel to the beam?
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unequal magnification
Foreshortening |
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Is x-ray film more sensitive to light or to x-rays?
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Light
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What defines fast film speed?
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Large crystals, thick emulsion and less exposure
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What defines slow film speed?
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small crystals, thin emulsions, more exposure
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What is more important screen speed or film speed?
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screen speed
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Since film is more sensitive to light, what is used to expose the film?
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Intensifying screens
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What can convert x-rays into light to expose the film?
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Intensifying screens.
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What are the 2 primary functions of a cassette?
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Lightproof box
Ensure intimate contact b/w the film & the screen |
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How does scatter radiation effect an image?
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Increases image blackness
decreases image contrast Adds no DX information |
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What is a collimator?
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An x-ray beam restriction device.
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What is collimation?
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Reduces the volume of tissue exposed, so less scatter is made.
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What is the purpose of a grid?
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It reduces scatter radiation from reaching the film and improves film contrast and image detail.
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What is a grid ratio?
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The ratio of the height of the lead strips to the distance between them.
Usually 8:1 or 12:1 |
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What does a higher grid ratio mean?
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Better scatter clean up and higher exposure
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What other 2 grid factors should you be aware of?
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Lines per inch= # of lead strips per inch (cm) of grid. greater lines per inch means better scatter clean up.
Focal Distance |
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What factors affect subject contrast?
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Atomic number
Physical density KvP |
