Large Animal Radiography
Chapter 19Radiology
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.