Transcript Welcome to Radiology

1
RADIOGRAPHIC POSITIONING:
AN OVERVIEW
RVT: Chapter 17
2
Learning Objectives
• Understand the proper anatomical positioning terminology
used in veterinary radiography
• Understand common rules for radiographic positioning
• Describe patient preparation and positioning aids
• Understand the normal required radiographic views
• List positioning guidelines
3
Rules of Positioning
• The view that the veterinarian requests will determine the
direction that the central beam will enter and exit the body.
• This is why most radiograph views have two names
• The first direction is the anatomical part the beam enters
• This anatomy is closest to the __________ __________
• The second is the direction the radiation exits the patient
• This piece of anatomy is closest to the __________ ____________
• Example: Ventrodorsal view
• Example: Dorsoventral view
*Combining 2 terms = usually use “o” as combining vowel
4
Abbreviations
• Abbreviated terms are often used to indicate
the direction of the x-ray beam as well
• First letter states where the x-ray beam
enters the body, the second designates
where it exits.
• V/D – enters ventrally and exits dorsally
• CrCd – enters cranial aspect of front or back leg
above carpus/tarsus and exits caudal aspect
5
Terminology
Recumbent:
• The animal is lying down when the radiograph is made.
• Most radiographs of the dog and cat are in a recumbent
position.
• This position should be presumed unless otherwise stated
on the radiograph.
6
Major Anatomical Planes
1. Mediolateral
2. Dorsopalmar/dorsoplantar
3. Cranial/Caudal
7
Limb Terminology
Caudal (Cd):
• Towards the tail from any given point
• Aspects of limbs _______ the carpal and
tarsal joints that face the rear of the animal
Cranial (Cr):
• Towards the head
• Aspects of the limb _____
the carpal and tarsal joints
that face toward the head
CrCd Femur
8
Limb Terminology
Dorsal (D):
• Upper aspect of the head, neck,
trunk, and tail
• Toward the spine of the animal
• Aspects of the legs distal to
and including the carpus and
tarsus joints that face “up” when
standing.
Dorsal Recumbency
9
Dorsal Aspect: Metacarpals
10
Limb Terminology
Palmar (Pa):
• Used instead of caudal when
describing the __________ from
the carpal joint distally
Plantar (Pl):
• Used instead of caudal when
describing the ____________
from the tarsal joint distally
DPa L Foot
11
Positional Terminology
Ventral:
• Lower aspect of the head, neck, trunk, and tail
• Also: towards the abdomen of the animal; towards the
ground when standing
Ventral
12
Positional Terminology
Lateral (L):
• From one side to the other
• Directional marker indicates
side _________ to cassette
R Lateral
Thoracolumbar
13
Directional Terminology
Mediolateral (ML):
• X-ray beam enters through
medial aspect and exits on the
lateral side
• Used mostly for limbs
ML Humerus
14
Directional Terminology
Lateromedial (LM)
• Beam enters the lateral aspect of the limb
• Beam exits the medial aspect
15
Positional Terminology
• Distal (Di)- away from the point of origin of a structure
• Proximal (Pr)- towards the point of origin of a structure
16
Positional Terminology
Rostral:
• Parts of the head positioned toward the _______
17
Terminology
Oblique (O):
•
•
•
Central ray passes obliquely through
patient (not parallel to one of the 3
major planes)
Patient is rotated slightly
The angulation varies
•
Anything other than parallel or
perpendicular
•
Why is this necessary?
•
Naming- hyphen usually separates
entry point from exit point
Ex: DPr-PaDi
18
Oblique Views
19
Positions?
20
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:
• Welfare of the patient
• Restraint and immobilization of the patient
• Make this the last thing you do
• Condition to the rotation of the anode
• Minimal trauma to the area of interest
• Lowest risk of radiation exposure for personnel
21
Radiographic
Restraint
22
Patient Factors
• Always consider your patient…
• Radiography can be scary
• Noises & confusion can be frightening
• The animal may be in pain
• “Less is more” with cats
• Patience is a virtue... May require sedation or general
anesthesia
• Always remember your client…
• This is someone’s baby, and it could be yours someday
23
Patient Preparation
• Clean & dry hair coat
• Remove splints, bandages*,
collars, leashes, etc.
• Chemical restraint is preferred but
not always allowed
• No matter how well behaved and
calm an animal seems, always
expect the worst when you expose!
24
Positioning Devices
Positioning devices should not be
placed directly above or below area of
interest – not completely radiolucent
25
Required Views
• Radiograph is a 2-D picture of a 3-D structure
• Norm: two views at right angles to one another
• Helps to visualize structures completely
• Area of interest is ________ to image receptor
• Minimizes distortion and magnification
• Comparison of two structures
• To compare to other area to see if there are any
pathological changes
• Sometimes veterinarians want the affected AND healthy
limb
26
Splitting the Cassette
• Used for taking more than 1 image on a single film
• Great for taking comparison views
• Use lead sheets or lead gloves (usually) to:
• Cover “non-used” portions of cassette to take first view,
then systematically uncover for subsequent and cover
previously imaged sections
• Not practical when using grid
• Split as many times as necessary
Tip: The 2 views need to be in the same direction!
27
Splitting the Cassette
28
Collimation, Collimation, Collimation
• Very important!
• Decreases scatter and
increases contrast.
29
Positioning Guidelines
• Center primary beam over area of interest
• Use caliper to measure thickest part
• Thickest part of anatomy towards cathode
30
Positional Marker Placement
• Lateral body rads: place cranial and ventral
• DP and CrCd limb views: place marker towards lateral
aspect of leg
• ML/LM limb views: place marker towards cranial aspect of
leg
These are general recommendations for consistency…not
the end of the world if this is missed.
31
Radiographic Checklist
• Image labeled & legible?
• Positional markers present?
• Good contrast & density?
• Anatomy roperly centered on film?
• Properly collimated?
• Correct positioning without rotation?
• Evidence of human exposure?
• Film properly developed?
• Artifacts present?
• Image diagnostic? Or repeat needed?