Radiographic Positioning: an overview RVT: Chapter 17

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

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

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

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.

Major Anatomical Planes Mediolateral Dorsopalmar/dorsoplantar Cranial/Caudal

Limb Terminology Caudal (Cd): Cranial (Cr): 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

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

Dorsal Aspect: Metacarpals

Limb Terminology Palmar (Pa): DPa L Foot 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

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

Positional Terminology Lateral (L): From one side to the other Directional marker indicates side _________ to cassette R Lateral Thoracolumbar

Directional Terminology Mediolateral (ML): X-ray beam enters through medial aspect and exits on the lateral side Used mostly for limbs ML Humerus

Directional Terminology Lateromedial (LM) Beam enters the lateral aspect of the limb Beam exits the medial aspect

Positional Terminology Distal (Di)- away from the point of origin of a structure Proximal (Pr)- towards the point of origin of a structure

Positional Terminology Rostral: Parts of the head positioned toward the _______

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

Oblique Views

Positions?

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

Radiographic Restraint

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

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!

Positioning Devices Positioning devices should not be placed directly above or below area of interest – not completely radiolucent

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

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!

Splitting the Cassette

Collimation, Collimation, Collimation Very important! Decreases scatter and increases contrast.

Positioning Guidelines Center primary beam over area of interest Use caliper to measure thickest part Thickest part of anatomy towards cathode

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.

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?