Ch. 19-Large Animal Radiography

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Large Animal Radiography

Chapter 19

Radiology

Introduction

Large animal radiography requires patience and time.

Radiography of large animals must be carefully planned to ensure safety of animal and personnel.

Terminology is the same, but generally will be radiographed in a standing position.

Special Considerations

Patient Restraint

Large animals can startle easily.

Let animal become familiar with machine.

Avoid sudden movements.

Restraint can be minimal, yet there is high risk to equipment.

Restraint methods include:

Twitch

Stocks

Sedation

Special Considerations

Continued

Equipment

Must have adequate power and maneuverability.

Three types of large animal x-ray units

1. small portable units

2. mobile units

3. mounted units

Small portable units

Lightweight and easy for transport.

Have maximum kVp generally around 90 and maximum mAs of 20.

Have to have longer exposure times due to lower kVp and mAs settings.

Longer exposure times increase likeliehood of motion.

May pose risk of greater radiation exposure.

Mobile Units

Can have 100-300 mA

Can have up to 120 kVp

Disadvantage is weight and lack of maneuverability.

Mounted Units

Common in large animal and specialty clinics for large animals.

May have capacity of greater than 1000mA.

Can be noisy due to how mounted and may distract the patient.

May have limited usefulness for studies on the feet due to producing obliquity of the views.

Patient Preparation

Hair should be brushed or washed to remove obvious dirt, bedding, and other artifacts.

Any liquid should be wiped dry.

If radiographing hoof may need to remove shoe, clean and trim the hoof. Will then pack foot with radiolucent material to prevent appearance of an air artifact.

Radiation Safety

Same rules apply as before, however due to size other things should be considered.

Attendant holding patient and holding the cassette next to the patient must be wearing appropriate protective attire.

Radiographer must ensure that all other personnel are a safe distance from the primary beam.

Cassette holders help to reduce radiation to attendants.

Positioning Devices

Positioning block- constructed of wood and raises the foot while holding the cassette.

Cassette tunnel- constructed of radiolucent wood or plastic and helps to hold cassette so that patient can be positioned directly on top of cassette without damaging the equipment.

Distal Phalanx (pedal bone)

Lateral View

X-ray beam is directed horizontally toward pedal bone.

View should include entire hoof.

Doropalmar/Dorsoplantar View

Cassette is placed directly behind the foot and x-ray beam is directed horizontally.

View should include entire hoof.

Dorsoplamar/Dorsoplantar Oblique View

Cassette is placed in tunnel cassette holder

Foot is centered on cassette and x-ray beam is angled to ground and directed at the hoof wall.

Navicular Bone

Dorsopalmar/Dorsoplantar Oblique View

Can be done as with Dorsopalmar/Dorsoplantar oblique view of distal phalanx.

Can be done on block specially designed with grooves that hold hoof at an angle.

X-ray beam is directed parallel to the ground.

View should include second and third phalanges.

Flexor View

Foot is placed on top of cassette in cassette tunnel.

Fetlock should be in extended position.

Proximal Phalanges

Lateral View (Short and Long Pastern)

X-ray beam is directed horizontally to phalanx.

View should include the first and second phalanges for a general projection of the area.

Dorsopalmar/Dorsoplantar View

Positioning same as for distal phalanges.

Fetlock Joint

Dorsopalmar/Dorsoplantar View

Cassette should be held perpendicular to the floor

View should include entire fetlock joint and a small portion of the bones that are proximal and distal to the joint.

Lateral View

Similar to other lateral views, with cassette remaining perpendicular to the floor.

Flexed Lateral View

Limb of interest is elevated and the fetlock joint flexed.

Cassette is positioned against the medial aspect of the joint.

X-ray beam is directed horizontally and parallel to the floor.

Collimate so attendant’s hands are not in view.

Oblique View (Lateral and Medial)

Positioned in normal weight bearing position.

Cassette is positioned so that the front of the x-ray beam is directed at a right angle to the cassette front.

Metacarpus/Metatarsus

Dorsopalmar/Dorsoplantar View

Cassette is held perpendicular to floor while beam is parallel to floor.

View should include joints above and below metacarpus and metatarus.

Lateral View

Same as other lateral views

Oblique View (Lateral and Medial)

This view is needed for an unobstructed view of the splint bones of the horse.

Carpus Joint

Dorsopalmar View

View should include entire carpus joint and a portion of the bones proximal and distal.

Lateral View

Same as before.

Flexed Lateral View

Limb of interest is elevated and attendant holds in a flexed position.

Oblique View (Lateral and Medial)

Same as before.

Skyline View

Limb is elevated, carpus is flexed.

Cassette placed firmly against dorsal region and should be nearly parallel with the floor as possible.

Tarsus Joint

Dorsoplantar

Field of view includes the entire tarsus and a portion of the adjacent bones distal and proximal.

Lateral View

Allows better visualization of the tibiotarsal joint.

Oblique Views (Lateral and Medial)

Same as before.

Elbow Joint

Craniocaudal View

Anesthesia is preferred.

X-ray beam is directed through the cranial aspect of the joint.

Lateral View

Patient is in a standing position, the limb of interest should be extended as far cranially as possible.

Field of view should include the entire elbow joint.

Shoulder Joint

Lateral View

X-ray beam is directed horizontally toward the medial side of the joint and perpendicular to the cassette.

Stifle Joint

Caudocranial View

Should be in standing position

Limb of interest should be stepped back in caudally extended, weight-bearing position.

Sedation is highly recommended.

Lateral View

Standing position.

Pelvis

Ventrodorsal View

General anesthesia is required (generally).

Need high-powered x-ray machine such as mobile or ceiling-mounted unit.

Skull

Lateral View

Natural standing posture, and the head is held without rotation.

Cassette is placed against the side of the skull with the lesion.

Guttural

Pouch/Larynx/Pharynx

Lateral View

Same as for skull views

Cassette is placed on the lateral side of the skull, with caudal skull centered on the cassette.

Dorsoventral View

Sedation.

X-ray tube positioned over the head with the x-ray beam directed perpendicularly to the cassette.

Teeth (Mandibular and

Maxillary)

Oblique Views

Cheek teeth are difficult to visualize on routine views.

Incisors can be taken by placing cassette in the mouth.

Sedation is required for intraoral radiography.

Cervical Spine

Lateral View

Patient can be standing.

Cervical spine runs along ventral portion of neck.

Must be exposed in 3 views

Base of skull, C-1 and C-2

C-3, C-4, and C-5

C-5, C-6, and C-7

Additional Views

Body portions can only be radiographed with a high powered unit.

Thorax

Four views usually required due to size

Patient is walked between tube and cassette.

Abdomen

Series of views recommended from Cranioventral and extending caudodorsal.

Thoracic Spine

X-ray beam is centered over the thoracic spine.

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