General General Principles of Principles of PositioningPositioning

Chapter 12Chapter 12

TerminologyTerminology CaudalCaudal: Parts of the head, neck and : Parts of the head, neck and

trunk positioned towards the tail from trunk positioned towards the tail from any given point. Also aspect of limbs any given point. Also aspect of limbs above the carpal and tarsal joints that above the carpal and tarsal joints that face the rear of the animal.face the rear of the animal.

CranialCranial- Describes parts of the neck, - Describes parts of the neck, trunk, and tail positioned toward the trunk, and tail positioned toward the head from any given point. Cranial also head from any given point. Cranial also describes those aspects of the limb above describes those aspects of the limb above the carpal and tarsal joints that face the carpal and tarsal joints that face toward the head. toward the head.

Terminology, cont.Terminology, cont. DistalDistal- Farther away from the point of origin - Farther away from the point of origin

of a structure.of a structure. DorsalDorsal- Upper aspect of the head, neck, trunk, - Upper aspect of the head, neck, trunk,

and tail. The term also means toward the and tail. The term also means toward the upper aspect of the animal. Dorsal also upper aspect of the animal. Dorsal also describes the aspects of the legs from the describes the aspects of the legs from the carpus and tarsus joints distally that face carpus and tarsus joints distally that face toward the head.toward the head.

LateralLateral- the x-ray beam enters through either - the x-ray beam enters through either the left or right side of the body and emerges the left or right side of the body and emerges on the opposite side, where the cassette is on the opposite side, where the cassette is positioned.positioned.

Terminology, contTerminology, cont MediolateralMediolateral- the x-ray beam enters a limb - the x-ray beam enters a limb

through the medial side and exits on the through the medial side and exits on the lateral side. Most lateral radiographs of lateral side. Most lateral radiographs of the limbs are taken in lateromedial the limbs are taken in lateromedial projection in large animal radiography.projection in large animal radiography.

PalmarPalmar- Used instead of caudal when - Used instead of caudal when describing the forelimb from the carpal describing the forelimb from the carpal joint distally.joint distally.

PlantarPlantar- Used instead of caudal when - Used instead of caudal when describing the hindlimb from the tarsal describing the hindlimb from the tarsal joint distally. joint distally.

And yet more And yet more TerminologyTerminology

Proximal-Proximal- Nearer to the point of Nearer to the point of origin of a structure.origin of a structure.

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

Almost DoneAlmost Done RostralRostral- parts of the head positioned - parts of the head positioned

toward the nares from any given point on toward the nares from any given point on the head.the head.

Superior and Inferior- Superior and Inferior- Used to describe Used to describe the upper and lower dental arcades, the upper and lower dental arcades, respectively.respectively.

VentralVentral- Lower aspect of the head, neck, - Lower aspect of the head, neck, trunk, and tail. The term also means trunk, and tail. The term also means toward the lower aspect of the animal. toward the lower aspect of the animal.

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

AbbreviationsAbbreviations Abbreviated term used for the position Abbreviated term used for the position

designates the direction of the x-ray beam.designates the direction of the x-ray beam. First letter states where the x-ray beam First letter states where the x-ray beam

enters the body, the second designates enters the body, the second designates where it exits. where it exits. V/D – enters ventrally and exits dorsallyV/D – enters ventrally and exits dorsally DMPaLO- indicates that carpus is rotated to a DMPaLO- indicates that carpus is rotated to a

selected -degree angle and the central x-ray selected -degree angle and the central x-ray enters the dorsal/medial surface and exits the enters the dorsal/medial surface and exits the palmar/lateral surface. palmar/lateral surface.

Basic Criteria of Basic Criteria of PositioningPositioning

Refrain from overt physical restraintRefrain from overt physical restraint Primary goal is to produce a good quality Primary goal is to produce a good quality

radiograph of the area being examined.radiograph of the area being examined. Factors to consider:Factors to consider:

1. Welfare of the patient.1. Welfare of the patient. 2. Restraint and immobilization of the 2. Restraint and immobilization of the

patient.patient. 3. Minimal trauma to area of interest.3. Minimal trauma to area of interest. The least risk of exposing those assisting The least risk of exposing those assisting

with the examination to radiaton.with the examination to radiaton.

Patient factorsPatient factors The comfort and welfare of the patient The comfort and welfare of the patient

should be considered at all times. should be considered at all times. PATIENCE!!!!!!PATIENCE!!!!!! Radiography can be frightening to Radiography can be frightening to

animal.animal. Noises of prep and of x-ray can be very Noises of prep and of x-ray can be very

disconcerting. Make sure take into disconcerting. Make sure take into consideration when taking radiographs.consideration when taking radiographs.

How to handle animalsHow to handle animals Handle in a slow, quiet, manner.Handle in a slow, quiet, manner. Use a calm, soft voice and reassure Use a calm, soft voice and reassure

animals through touch. animals through touch. Avoid quick, loud movements.Avoid quick, loud movements. Avoid and severe restraint.Avoid and severe restraint.

Prep soundsPrep sounds When depressing prep button, When depressing prep button,

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

General PositioningGeneral Positioning May require sedation, general May require sedation, general

anesthesia, and positional devicesanesthesia, and positional devices All essential anatomical regions All essential anatomical regions

should be included in the primary should be included in the primary beam when taking x-raysbeam when taking x-rays

PRIMARY GOAL- to find the most PRIMARY GOAL- to find the most comfortable posture/position for the comfortable posture/position for the animal to produce an accurate animal to produce an accurate reproduction of the area of interestreproduction of the area of interest

PREPARATION!!!PREPARATION!!! Prepare, prepare, preparePrepare, prepare, prepare

Prior to radiograph being taken make Prior to radiograph being taken make sure:sure: Correct patient is presentCorrect patient is present All chemicals and processor are in working All chemicals and processor are in working

order.order. That cassette is positioned appropriately.That cassette is positioned appropriately. That identifying markers are in place.That identifying markers are in place.

MeasurementMeasurement CaliperCaliper- measuring device for - measuring device for

anatomic area of interest.anatomic area of interest. Measures area in centimetersMeasures area in centimeters If unsure, always measure thickest If unsure, always measure thickest

spot. If large differences in sizes spot. If large differences in sizes exist, may have to take two separate exist, may have to take two separate radiographs.radiographs.

Required ViewsRequired Views Radiograph is a two dimensional picture of Radiograph is a two dimensional picture of

a three-dimensional structure.a three-dimensional structure. Therefore two views must be taken at right Therefore two views must be taken at right

angles to one another in order to get a good angles to one another in order to get a good idea of structure of anatomy.idea of structure of anatomy.

2 views will help you see something that you 2 views will help you see something that you might miss on 1 viewmight miss on 1 view

Area of interest closest to filmArea of interest closest to film Minimizes distortion and magnificationMinimizes distortion and magnification

ComparisonComparison To compare to other area to see if there are any To compare to other area to see if there are any

pathological changespathological changes

Splitting the CassetteSplitting the Cassette Taking more than 1 picture on a cassetteTaking more than 1 picture on a cassette You need to place lead over the “non-used” You need to place lead over the “non-used”

portion of the cassette, take the exposure, portion of the cassette, take the exposure, remove the lead, cover the “exposed” side remove the lead, cover the “exposed” side and expose the “non-exposed” sideand expose the “non-exposed” side Lead gloves can be used – inexpensive, handyLead gloves can be used – inexpensive, handy

Not practical when using bucky trayNot practical when using bucky tray Split as many times as you have roomSplit as many times as you have room The 2 views need to be in the same The 2 views need to be in the same

directiondirection

Collimation, Collimation, Collimation, Collimation, CollimationCollimation

Very importantVery important Decreases the amount of scatterDecreases the amount of scatter

Which increases the amount of contrastWhich increases the amount of contrast Have you heard this before??????Have you heard this before??????

Positioning GuidelinesPositioning Guidelines Should be Taken over Thickest areaShould be Taken over Thickest area General Rule:General Rule:

The center of the primary beam (+) should The center of the primary beam (+) should be directly in the center of the area of be directly in the center of the area of interest.interest.

CASSETTE SIZE IS IMPERATIVECASSETTE SIZE IS IMPERATIVE Specific anatomy must be included for Specific anatomy must be included for

each anatomic area.each anatomic area. Long bones should include the shaft of the bone, Long bones should include the shaft of the bone,

as well as the joint above and the joint belowas well as the joint above and the joint below Joints should have the beam centered over the Joints should have the beam centered over the

joint space, and the small portion of long bones joint space, and the small portion of long bones above and below the joint.above and below the joint.

Patient PreparationPatient Preparation Clean & dry hair coatClean & dry hair coat Removal of splints, bandage material, collars, Removal of splints, bandage material, collars,

leashes, etc.leashes, etc. Chemical restraint is preferred but not always Chemical restraint is preferred but not always

allowed allowed No matter how good an animal seems, always expect No matter how good an animal seems, always expect

the worsethe worse Use of positioning devicesUse of positioning devices

Sandbags, foam blocks, wood blocks, trough, tape, Sandbags, foam blocks, wood blocks, trough, tape, gauze, ropegauze, rope

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

Film IdentificationFilm Identification Proper labeling of a radiograph is Proper labeling of a radiograph is

mandatory for legal and practical reasons.mandatory for legal and practical reasons. Should include:Should include:

Appropriate patient identificationAppropriate patient identification Appropriate markers (R ) (L) and view if Appropriate markers (R ) (L) and view if

necessary.necessary. Should mark side that is down on the patient. Should mark side that is down on the patient. Lateral projections of the leg should have the Lateral projections of the leg should have the

marker placed cranially to the leg. marker placed cranially to the leg.

ViewsViews

Standard is a lateral view and v/d or d/v Standard is a lateral view and v/d or d/v view.view.

Oblique viewOblique view Patient is rotated – not the tube headPatient is rotated – not the tube head Degree of angulations varies on area of interest – Degree of angulations varies on area of interest –

usually pretty minimal = 10 to 15 degree’susually pretty minimal = 10 to 15 degree’s They allow for a more dimensional viewThey allow for a more dimensional view

Eliminates superimpositionEliminates superimposition Comparison ViewsComparison Views

Compare R w/ LCompare R w/ L Young animals, extremities – most commonYoung animals, extremities – most common Helpful to do both projections on 1 filmHelpful to do both projections on 1 film