Transcript General Principles of Positioning

General Principles of
Positioning
Chapter 12
Terminology
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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.
Terminology, cont.
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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.
Terminology, cont
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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.
And yet more Terminology
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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.
Almost Done
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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.
Abbreviations
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Left (L)
Right (R)
Dorsal (D)
Medial (M)
Lateral (L)
Cranial (Cr)
Rostral (R)
Caudal (Cd)
Palmar (Pa)
Oblique (O)
Plantar (Pl)
Abbreviations
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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
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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
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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.
How to handle animals
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Handle in a slow, quiet, manner.
Use a calm, soft voice and reassure animals
through touch.
Avoid quick, loud movements.
Avoid and severe restraint.
Prep sounds
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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.
General Positioning
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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
PREPARATION!!!
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Prepare, prepare, prepare
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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
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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.
Required Views
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Radiograph is a two dimensional picture of a threedimensional structure.
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2 views will help you see something that you might miss on
1 view
Area of interest closest to film
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Therefore two views must be taken at right angles to one
another in order to get a good idea of structure of anatomy.
Minimizes distortion and magnification
Comparison
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To compare to other area to see if there are any pathological
changes
Splitting the Cassette
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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
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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
Collimation, Collimation,
Collimation
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Very important
Decreases the amount of scatter
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Which increases the amount of contrast
Have you heard this before??????
Positioning Guidelines
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Should be Taken over Thickest area
General Rule:
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The center of the primary beam (+) should be directly in
the center of the area of interest.
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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
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Clean & dry hair coat
Removal of splints, bandage material, collars, leashes, etc.
Chemical restraint is preferred but not always allowed
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No matter how good an animal seems, always expect the
worse
Use of positioning devices
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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
Film Identification
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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
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Standard is a lateral view and v/d or d/v view.
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Oblique view
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Patient is rotated – not the tube head
Degree of angulations varies on area of interest – usually pretty
minimal = 10 to 15 degree’s
They allow for a more dimensional view
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Eliminates superimposition
Comparison Views
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Compare R w/ L
Young animals, extremities – most common
Helpful to do both projections on 1 film