1. INTRODUCTION TO POSITIONING Chapter 17
PART B POSITIONING
INTRODUCTION TO POSITIONING Chapter 17
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

2. Chapter Outline Objectives Key Terms Overview of Positioning
Positional Terminology
Patient Positioning
Viewing Radiographs
Radiographic Checklist
Key Points
Review Questions
Bibliography
When you have finished this chapter, you will be able to:
1. Understand the proper anatomic positioning terminology used in veterinary radiography.
2. Indicate the common rules for radiographic projections that are used when identifying and radiographing animals.
3. Apply the various principles of nonmanual restraint and animal handling so that the patient does not need to be manually restrained when being radiographed.
4. Describe standard safety procedures that should always be followed when any radiograph is taken.
5. Describe patient preparation that should be completed prior to the taking of a radiograph.
6. Describe the advantages and disadvantages of the various positioning aids available.
7. Know the required views.
8. List positioning guidelines to ensure production of good quality diagnostic radiographs.
9. Explain how the three important principles of radiation safety are used to protect the radiographer.
10. Describe when and how dividing the cassette should be used.
11. Describe important issues for labeling and identifying an image.
12. Properly place a radiograph on the illuminator.
13. Using a checklist, determine whether a radiograph is diagnostic.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

3. Overview Of Positioning
Important to consider human and animal safety
Use nonmanual restraint
Use chemical restraint where possible
Utilize behavior, restraint, and positioning principles
Follow the three tenants of safety
Distance, shielding, and time
Be familiar with normal anatomy
Positioning focuses on nonmanual restraint.
Veterinary medicine is practically the only health science field in which the radiographer seems to feel the need to restrain the patient while the exposure is being made.
If proper positioning is to occur with nonmanual restraint, the patient should be immobilized either by chemical restraint (sedation or general anesthesia) and /or positional devices.
Overt manual restraint should be minimized. Even if chemical restraint is contraindicated, common behavior, restraint, and positioning principles can be applied to minimize radiographer exposure.
The canine patient usually responds to a calm, authoritative approach, whereas a feline patient resists too much restraint.
If manual restraint is necessary, the radiographer must take all the precautions necessary to minimize being exposed to ionizing radiation.
The welfare of both the patient and the radiographer should be kept in mind during the production of accurate diagnostic radiographs.
If manual restraint cannot be avoided, minimum safety procedures should be followed.
All personnel in the radiographic suite during exposure must be shielded properly with the appropriate leaded apparel.
As is also stressed in the chapter on safety, judicious adherence to distance, protection, and time helps minimize radiation exposure to the restrainer.
It is also essential that one be familiar with normal anatomy of the species and the proper terminology. A basic understanding of what is normal assists in producing diagnostic radiographs for accurate interpretation and diagnosis by the veterinarian.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

4. General Positional Terminology
1. Radiographic projections are named according to the direction in which the central beam anatomically enters the body part, followed by the area of exit of the xray beam.
2. Many projections require combinations of basic directional terms to accurately describe the point of entrance and point of exit. It is recommended that these terms be combined in a consistent order to increase standardization of the nomenclature. With the use of an overhead vertical beam, the position in which a:
a. Patient is lying on its back (dorsal recumbency) is called VD (ventrodorsal). The beam goes in the ventral (V) portion—the abdomen—and exits on the dorsal (D)aspect or the back (see Figure 17-2).
b. Patient is lying on its abdomen (ventral recumbency) is called DV (dorsoventral). The beam goes in the dorsal (D) portion—the back—and exits on the ventral (V)aspect or the abdomen.
TECHNICIAN NOTES
Remember that according to etymological rules, when you combine two terms, the combination of the root and the combining vowel (generally “o”) is used.
For lateral recumbency, the image is labeled according to the side the patient is lying on. Thus in a right lateral image, the patient is lying on its right side. The right limb in this case would be the side against the image receptor Technically a right lateral radiograph is properly referred to as a-Le-RtL).(Conventionally for ease of description, only the area of exit is included [Right lateral.])
The terms right and left are not used in combination with other terms and should precede any other terms (e.g., right lateral).
The terms medial (M) and lateral (L) should be subservient (go second) when used in combination with other terms (e.g., dorsomedial).
On the head, neck, trunk and tail, the terms rostral (R), cranial,(Cr) and caudal (Cd) should take precedence (go first) when used in combination with other terms (e.g., caudoventral).  .
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

5. Limb Terminology
1. The descriptors dorsal (D), palmar,(Pa) and plantar (Pl) are used for that portion of the limb distal to and including the radius and tibia.
2. Palmar (Pa) is used in reference to the forelimbs, whereas plantar (Pl) refers to the hind limbs.
3. Cranial (Cr) and caudal (Cd) refer to the portion of the limb proximal to the carpus and tarsus.
4. In describing the limbs, the terms dorsal, palmar, plantar, cranial, and caudal should take precedence when used in combination with other terms. Example: dorsoproximal.
5. The term oblique (O) is added to the names of those projections in which the central ray passes obliquely (not parallel) to one of the three major directional axes—mediolateral (ML), dorsopalmar/ dorsoplantar (DP) or craniocaudal (CrCd) through the body part.
a. Thus, in a dorsomedial-palmarolateral oblique (DM-PaLO) image of the carpus, the beam enters the dorsomedial aspect of the carpus and exits the palmarolateral aspect of the carpus (Figure 17-3).
b. Technically, if this view was made by positioning the xray tube 60 degrees laterally from the dorsal side, the designation would be D60°M-PaLO. This is discussed further in the large animal chapter (26).
6. In those views requiring a combination of directional terms, a hyphen should be inserted to separate the point of entry and point of exit, for example, palmaroproximal-palmarodistal (PaPr-PaDi) of a horse limb.
This means that the beam comes from the front of the foot and exits at the back of the foot. The plate is placed at the back of the foot).
7. The tangential or skyline views require no special designation because the point of entry to point of exit method describes these views concisely; for example, proximodorsal-distodorsal views (PrD-DiD) in reference to an equine navicular.
The beam aims from top (proximo-) to bottom (disto-) at the back(dorsal) of the leg,.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

6. Oblique Limb Terminology
The term oblique (O) is added to the names of those projections in which the central ray passes obliquely (not parallel) to one of the three major directional axes—mediolateral (ML), dorsopalmar/ dorsoplantar (DP) or craniocaudal (CrCd) through the body part.
They are named in the same manner as the standard views.
The term oblique is generally used in reference to limbs.
a. Thus, in a dorsomedial-palmarolateral oblique (DM-PaLO) image of the carpus, the beam enters the dorsomedial aspect of the carpus and exits the palmarolateral aspect of the carpus.
b. Technically, if this view was made by positioning the xray tube 60 degrees laterally from the dorsal side, the designation would be D60°M-PaLO.
This is discussed further in the large animal chapter (26).
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

7. Patient Concerns and Positioning
BE PATIENT
Handle patients slowly and quietly
Have the room darkened if lightly sedated
Do not overrestrain, especially cats
Use restraint devices if needed
Desensitize rotor noise
Use proper exposures and collimate
Wear protective clothing
Stay as far from beam as possible
Minimize digital dose creep
Patient clean and free of debris
Proper preparation may mean being able to temporarily step away from scatter radiation for at least the canine lateral views, even without chemical restraint.
Patient Preparation
The patient should be clean and free of any debris.
If the hair coat of the patient is wet or full of debris, confusing artifacts can appear on the radiograph.
Collars, harnesses, and leashes of any sort, especially those made of metal, should be removed.
Unless there is a definite medical reason for leaving them in place, remove bandages, splints, and casts before radiography.
Pedal radiography of the horse may require removing the shoe and cleaning the frog of the foot to minimize any artifacts that may obscure an area of interest.
For radiography of the small animal abdomen, the gastrointestinal tract must be free of ingesta and fecal material.
A cathartic such as an enema or a laxative may be indicated to remove the obstructive material.
A more detailed discussion of patient preparation for abdominal study is in chapter 25.
Figure commercially available cat scruffer.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

8. Human Safety Use positioning aids and be creative.
Avoid manual restraint when the exposure is being made.
Create an illusion that the animal is held .
Have everything ready prior to taking the exposure
Positioning Aids
Devices such as sandbags, foam blocks and wedges, wood blocks, and a radiolucent trough can be used.
Tape, gauze, rope, and compression bands are also useful positioning aids. Any reusable aids should be waterproof, washable, and stain resistant as well as easy to store.
Positioning devices are commercially available. Commercial foam available in various shapes and sizes is generally covered in washable heavy vinyl covers.
Foam tends to produce an air density shadow, and if not properly covered, to absorb and retain liquids that may be radiopaque when dry. Depending on what they are covered with, foam blocks may also leave density shadows on the processed radiograph.
U- and V-shaped troughs are essential to maintain a patient in dorsal recumbency. Generally they are clear plastic or vinyl-covered. If using for areas such as the pelvis, keep the trough fully outside the collimated area for the same reasons.
Tape, gauze, and compression bands are extremely effective. A wooden spoon can be used to keep a cat’s head out of the field of view. Compression band and hook-and-loop tape (Velcro) can be applied. Clothes pegs/pins for cats or a commercially available cat scruffer (applied to the dorsal neck region [a feline behavior principle that the queen uses with her kittens]) is also effective.
Your own devices can be made at a fraction of the cost of the commercially available positioning devices.
Positioning aids can give the patient the illusion that it is being held. Strategically placed sandbags or compression devices over the neck and limbs, a dimly lit room, calm deliberate movements, and a gloved hand placed over the head and held until the rotor is depressed may keep patients, especially dogs, in lateral recumbency, calm long enough for the restrainer to step back at least 6 feet.
The moment the rotor is depressed, slip your hand out of the glove, leaving it over the animal’s head so the patient assumes that you are still there. Then quietly step back. Move forward as soon as the radiograph has been taken.
Another person should be depressing the exposure buttons on the console; if you are using the foot pedal, step back as far as possible. Increasing your distance from the beam drastically reduces your exposure.
If there is no alternative but to restrain a patient, it is imperative to look away from the field of view and lean back as far as possible while taking the radiograph.
At no point should any part of your body be in the field of view. Protective equipment protects you from scatter radiation, not from the primary beam.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

9. Required Views and Positioning Guidelines
Generally:
Avoid magnification and distortion
Suggestions
Two views of each anatomic area taken at right angles to each other are the minimum recommended exposures.
You are trying to visualize a three-dimensional body on two-dimensional image, so details will be missed if two perpendicular views are not taken).
There may be exceptions if the patient is debilitated or in trauma and further positions other than the lateral will cause undue stress to the animal.
A horizontal beam radiograph could then be considered. If you position the area of interest closest to the image receptor, there will be a reduction in distortion and less magnification of the area under examination.
When radiographing a limb, especially in immature or older patients, consider imaging the opposite corresponding limb to allow the pathologic structure of one limb to be compared with the normal anatomy of the other.
When tabletop technique is used, an image receptor can be divided to view more than one view and thus limit the number of radiographs utilized.
Place a lead sheet over half of the cassette to prevent exposure while the other side is being radiographed.
The image receptor should still be collimated to only that half so that scatter and secondary radiation will not cause unnecessary fogging of the image.
Lead sheets, which can be purchased from most xray supply companies, are usually supplied in preselected sizes, or larger sheets can be purchased and cut to the desired size.
The lead should be at least 2 mm thick. If a lead sheet is unavailable, a lead glove can be placed over the area to be shielded.
When using tabletop technique, place a nonslip pad under the cassette to keep it from slipping.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

10. Measure Correctly
The patient should be measured while in the same position used for the radiograph; if the animal is measured while standing, for example, the tissue thickness measurement will be greater than when the animal is recumbent, especially for soft tissue studies.
If there is a large difference in tissue thickness between the cranial and caudal borders, which is not uncommon in the abdomen and thorax of a deep-chested dog, two separate exposures may need to be taken.
A compromise is best made if there is only a small difference in tissue density.
Use an image receptor that is large enough to cover the body area being radiographed.
Specific anatomy must be included for each anatomic area.
For example, all radiographs of long bones (humerus and femur) should include the shaft of the bone as well as the joints both distal (Di) and proximal (Pr) to the bone.
For joint radiography, the central ray must be centered over the joint space, and the beam should include a portion of the long bones distal and proximal to the joint. This is further expanded in Chapters 20 and 21.
When two separate views will be positioned on a radiograph, both views should be facing the same direction.
For limbs, this would mean that the toes are facing the same side of the cassette; for the skull, the nose is in the same direction on each view.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

11. Remember
In general, the central ray should be centered directly over the area of interest.
If there is a known lesion, however, it is important to center the beam directly over this area, especially to visualize fracture healing in limbs or spinal lesions.
If the central ray is not directly over the area of interest, distortion and misdiagnosis may occur.
The measurement for any anatomic region is generally taken over the thickest part.
This practice ensures that all regions of the area of interest will be penetrated with sufficient exposure factors.
A caliper is used to measure the anatomic area of interest so that proper exposures can be made.
This is an inexpensive device that measures part thickness in centimeter increments
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

12. Film Identification Required legally
Use positioning markers appropriately
Identification (ID) of the radiographs is important both for legal purposes and for knowledge that the radiographs belong to the patient in which you are interested. Please see Chapter 5 on image receptor imaging for further specific information.
Be sure that each radiograph contains the following information: names of the owner and animal, date of examination, and the name of the clinic.
Additional helpful information includes age, breed, and sex of the patient, but this can be written instead in the radiography log.
Positioning markers (right, left, front, hind) should be used so that the radiographs may be correctly interpreted.
This is especially true for equine radiographs of areas distal to the carpus and tarsus or symmetrical anatomical areas such as a skull in most animals.
By convention, for limbs, place markers laterally (as opposed to medially) for DP, CrCd or CdCr, and oblique radiographs.
Place the markers cranially for lateral radiographs.
In DV or VD views, place the appropriate L or R marker on the correct side of the animal.
When a lateral projection of the body is taken, the marker should indicate the side that is down on the table or cassette. Thus an R would indicate a patient lying in right lateral recumbency.
The marker or label would generally be placed cranially and ventrally in lateral recumbency
When a special procedure is performed, such as a gastrointestinal contrast study that is part of a series, radiographs that identify time elapsed or order taken are also important. In this case the series should be labeled with the appropriate time elapsed in hours and minutes. This designation can be made on the lead tape label, or specialized time clocks can be used in which it is easy to adjust the time lapse. Gravity markers that indicate that a patient is standing are also available, although not frequently used.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

13. Viewing the Radiograph
Viewing Radiographs
To assist in understanding normal radiographic anatomy, you should always view radiographs on the illuminator in the following manner.
Lateral radiographs: The cranial part of the animal is to your left.
Dorsoventral/ventrodorsal radiographs: The cranial part of the animal points up and the animal’s left side is on your right (as if you are going to shake its paw).
Lateral or oblique radiographs of the limbs: The proximal part of the limb points up and the cranial or dorsal aspect of the limb is to your left.
DP/PD/CrCd/CdCr radiographs: The proximal end of the extremity is at the top of the illuminator
Consistency is important.
When labeling film radiographs, consider how the labels and markers are positioned so that they can easily be read when the radiographs are viewed in the proper positions.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

14. Radiographic Check List
Properly labeled, and indicated?
Exposure factors?
Centered?
Borders and collimation?
Patient properly positioned?
No gloves!!!!
Properly processed?
Minimal artifacts?
If no:
Diagnostic?
Repeat?
Before submitting the radiographs to the veterinarian, you should ask yourself the following questions to ensure that you have optimal diagnostic and legal radiographs:
Is the image labeled and legible?
Are positional lead markers present?
Do you have good exposure with appropriate contrast and density?
Is your image properly centered?
Are the appropriate borders included, and is there evidence of collimation?
Is the body part properly positioned, with no rotation?
Is there no evidence of a human exposure, such as a glove?
Is the film properly developed (if applicable)?
Have artifacts been kept to a minimum to prevent interference with the image?
If the answer is no to any of these questions, consider the next two:
Is the image diagnostic?
Does the image need to be repeated?
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

15. Key Points Projection described as entry and exit Proper terminology
Area of interest closest to film
Human safety at all times
Plan carefully and minimize retakes
Use chemical restraint if possible
Position with knowledge and creativity
Keep movements calm and slow
Place positional markers correctly
View the radiograph correctly
1. The radiographic projection is described according to where the beam enters and exits the area of interest.
2. For pectoral limbs, use the term dorsopalmar (DPa) to designate the area distal to and including the carpus. For pelvic limbs, dorsoplantar (DPl) is used to designate the area distal to and including the tarsus.
3. The area of interest should be closest to the image receptor.
4. Keep human safety in mind at all times, utilizing the three important safety principles of time, distance, and shielding.
5. Careful planning and preparation help minimize retakes.
6. Use chemical restraint if possible.
7. Knowledge of the proper positioning technique along with creativity leads to inventive and effective use of positioning aids and nonmanual restraint.
8. Generally utilize slow and deliberate movements in a dimly lit room to keep the patient calm.
9. When identifying limbs, place the markers laterally for DP, CrCd, or CdCr views and cranially for lateral views.
10. When looking at radiographs on the viewer, position for a VD/DV so that you are “shaking its paw” or looking at the ventral aspect. For a lateral view, have the animal’s head to your left.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.

16. Mystery Radiograph What do you think the different objects are?
The left side is a styrofoam cup with a little water in the bottom. The upper image on the left is ice cubes.
Grapes are at the upper portion of the right image, and water and ice are in the 2 cups. The purpose was to show what happens with the difference in density and the overlapping of the patient as in the overlapping grapes.
The exposure factors were equivalent in both cases.
Brown: Lavin’s Radiography for Veterinary Technicians Copyright © 2014, 2007, 2003, 1999, 1994 by Saunders, an imprint of Elsevier Inc.