General%20Principles%20of%20Positioning

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General Principles of Positioning

• Chapter 12

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Terminology

• Caudal Parts of the head, neck and trunk
  positioned towards the tail from any given point.
  Also aspect of limbs above the carpal and tarsal
  joints that face the rear of the animal.
• Cranial- Describes parts of the neck, trunk, and
  tail positioned toward the head from any given
  point. Cranial also describes those aspects of
  the limb above the carpal and tarsal joints that
  face toward the head.

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Terminology, cont.

• Distal- Farther away from the point of origin of
  a structure.
• Dorsal- Upper aspect of the head, neck, trunk,
  and tail. The term also means toward the upper
  aspect of the animal. Dorsal also describes the
  aspects of the legs from the carpus and tarsus
  joints distally that face toward the head.
• Lateral- the x-ray beam enters through either
  the left or right side of the body and emerges on
  the opposite side, where the cassette is
  positioned.

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Terminology, cont

• Mediolateral- the x-ray beam enters a limb
  through the medial side and exits on the lateral
  side. Most lateral radiographs of the limbs are
  taken in lateromedial projection in large animal
  radiography.
• Palmar- Used instead of caudal when describing
  the forelimb from the carpal joint distally.
• Plantar- Used instead of caudal when describing
  the hindlimb from the tarsal joint distally.

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And yet more Terminology

• Proximal- Nearer to the point of origin of a
  structure.
• Recumbent- The animal is lying down when the
  radiograph is made. Most radiographs of the dog
  and cat are made with the animal in the recumbent
  position, and this position should be presumed
  unless otherwise stated on the radiograph.

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Almost Done

• Rostral- parts of the head positioned toward the
  nares from any given point on the head.
• Superior and Inferior- Used to describe the upper
  and lower dental arcades, respectively.
• Ventral- Lower aspect of the head, neck, trunk,
  and tail. The term also means toward the lower
  aspect of the animal.

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Abbreviations

• Left (L)
• Right (R)
• Dorsal (D)
• Medial (M)
• Lateral (L)
• Cranial (Cr)
• Rostral (R)
• Caudal (Cd)
• Palmar (Pa)
• Oblique (O)
• Plantar (Pl)

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Abbreviations

• Abbreviated term used for the position designates
  the direction of the x-ray beam.
• First letter states where the x-ray beam enters
  the body, the second designates where it exits.
• V/D enters ventrally and exits dorsally
• DMPaLO- indicates that carpus is rotated to a
  selected -degree angle and the central x-ray
  enters the dorsal/medial surface and exits the
  palmar/lateral surface.

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Basic Criteria of Positioning

• Refrain from overt physical restraint
• Primary goal is to produce a good quality
  radiograph of the area being examined.
• Factors to consider
• 1. Welfare of the patient.
• 2. Restraint and immobilization of the patient.
• 3. Minimal trauma to area of interest.
• The least risk of exposing those assisting with
  the examination to radiaton.

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Patient factors

• The comfort and welfare of the patient should be
  considered at all times.
• PATIENCE!!!!!!
• Radiography can be frightening to animal.
• Noises of prep and of x-ray can be very
  disconcerting. Make sure take into consideration
  when taking radiographs.

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How to handle animals

• Handle in a slow, quiet, manner.
• Use a calm, soft voice and reassure animals
  through touch.
• Avoid quick, loud movements.
• Avoid and severe restraint.

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Prep sounds

• When depressing prep button, machine will make
  noise. It is good idea to let patients hear this
  sound as you are positioning so as to avoid the
  frightening newness of the sound once the
  radiograph is taken.

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General Positioning

• May require sedation, general anesthesia, and
  positional devices
• All essential anatomical regions should be
  included in the primary beam when taking x-rays
• PRIMARY GOAL- to find the most comfortable
  posture/position for the animal to produce an
  accurate reproduction of the area of interest

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PREPARATION!!!

• Prepare, prepare, prepare
• Prior to radiograph being taken make sure
• Correct patient is present
• All chemicals and processor are in working order.
• That cassette is positioned appropriately.
• That identifying markers are in place.

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Measurement

• Caliper- measuring device for anatomic area of
  interest.
• Measures area in centimeters
• If unsure, always measure thickest spot. If
  large differences in sizes exist, may have to
  take two separate radiographs.

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Required Views

• Radiograph is a two dimensional picture of a
  three-dimensional structure.
• Therefore two views must be taken at right angles
  to one another in order to get a good idea of
  structure of anatomy.
• 2 views will help you see something that you
  might miss on 1 view
• Area of interest closest to film
• Minimizes distortion and magnification
• Comparison
• To compare to other area to see if there are any
  pathological changes

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Splitting the Cassette

• Taking more than 1 picture on a cassette
• You need to place lead over the non-used
  portion of the cassette, take the exposure,
  remove the lead, cover the exposed side and
  expose the non-exposed side
• Lead gloves can be used inexpensive, handy
• Not practical when using bucky tray
• Split as many times as you have room
• The 2 views need to be in the same direction

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Collimation, Collimation, Collimation

• Very important
• Decreases the amount of scatter
• Which increases the amount of contrast
• Have you heard this before??????

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Positioning Guidelines

• Should be Taken over Thickest area
• General Rule
• The center of the primary beam () should be
  directly in the center of the area of interest.
• CASSETTE SIZE IS IMPERATIVE
• Specific anatomy must be included for each
  anatomic area.
• Long bones should include the shaft of the bone,
  as well as the joint above and the joint below
• Joints should have the beam centered over the
  joint space, and the small portion of long bones
  above and below the joint.

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Patient Preparation

• Clean dry hair coat
• Removal of splints, bandage material, collars,
  leashes, etc.
• Chemical restraint is preferred but not always
  allowed
• No matter how good an animal seems, always expect
  the worse
• Use of positioning devices
• Sandbags, foam blocks, wood blocks, trough, tape,
  gauze, rope
• Positioning devices should not be placed directly
  above or below area of interest not completely
  radiopaque

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Film Identification

• Proper labeling of a radiograph is mandatory for
  legal and practical reasons.
• Should include
• Appropriate patient identification
• Appropriate markers (R ) (L) and view if
  necessary.
• Should mark side that is down on the patient.
• Lateral projections of the leg should have the
  marker placed cranially to the leg.

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Views

• Standard is a lateral view and v/d or d/v view.
• Oblique view
• Patient is rotated not the tube head
• Degree of angulations varies on area of interest
  usually pretty minimal 10 to 15 degrees
• They allow for a more dimensional view
• Eliminates superimposition
• Comparison Views
• Compare R w/ L
• Young animals, extremities most common
• Helpful to do both projections on 1 film

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