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 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.