large animal radiology

Bones of the Head
Teeth
No. of Ribs- 18 ribs
GI Tract- hindgut
Distal Limbs
anatomy review of large animal:
horse skeleton
horse skeleton
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skull of a horse
skull of a horse
Horse skull from above
Horse skull from above
front leg of a horse
front leg of a horse
back leg of a horse
back leg of a horse
lower part of the front leg of a horse
lower part of the front leg of a horse
horse hoof
horse hoof
Difficult to take the patient to the x-ray machine, so take the x-ray machine to the patient
Most views will be taken in standing position
Restraint
Safety
Equipment
Preparation
Positioning Devices
Special Considerations in large animal radiology
Patience, time, quiet environment
Prey animals- introduce them to the machine and let them get comfortable
Horse kicks machine = BAD
Horse kicks radiographer = WORSE
Stocks, twitch, or your best friend- sedation
If none of the above possible, raise the limb opposite of the one being radiographed
Restraint in large animal radiology
Machine must be powerful and mobile; must be able to produce horizontal and vertical beam
Portable Unit- used in farm call practice
Usually lower mA and kVp, requiring longer exposure
Mobile Unit- more powerful (100-300 mA)
Weighs more; more cumbersome to move around
Mounted Unit- used in specialty and referral practices; ceiling mounted on rail system
Capacity 1000 mA or more
Equipment needed for large animal radiology
portable x-ray machine
portable x-ray machine
Brush dirt, bedding and surface artifacts from coat
If must wash down, dry haircoat with towel
Horse feet:
Remove shoes and trim overgrown hoof
Sole, cleft, frog: pick and scrub clean, then pack with radiolucent material (softsoap, play-doh, methylcellulose
Patient Preparation
x-ray of a hoof
The central and collateral sulci of the foot have been packed with a pliable material of similar radiopacity as the sole (Play-Doh). B, Dorsal 65-degree proximal-palmarodistal view of a normal P3 with the sulci packed. Note the good definition of vascular channels without superimposed air artifacts.
x-ray of a hoof
All radiation safety rules apply- badges, aprons, gloves, shields
Assistants will be watching horse, so it is the job of the radiographer to assure that all personnel in the room are safe!!!!
Use cassette holding devices- clamp on pole with handle
Radiation Safety
Used to hold cassette in position and to raise foot from the floor
Positioning block- wooden block with slot on one side to hold cassette perpendicular to floor
Cassette Tunnel- radiolucent cover for cassette, strong enough to withstand weight of animal – wood or hard plastic
Positioning Devices
Lateral View
Beam center: hoof wall just below coronary band
Field of view: entire hoof
Place hoof on wood block, as close to the edge as possible
Place cassette vertically behind hoof, as close to the medial surface as possible
Object to film distance must be minimal
The same positioning is used for a lateral navicular bone exposure
Distal Phalanx (Pedal Bone)
Place hoof on woodblock to center the horizontal beam over the pedal bone, just below the coronary band
Cassette placed perpendicular to floor to center hoof in view
Place hoof as close to cassette as possible
Field of view: entire hoof
May need to lift opposite leg
Dorsopalmar/Dorsoplantar View
Cassette placed in tunnel cassette holder and hoof centered on top of tunnel holder
Beam centered over hoof wall just below coronary band
X-ray tube angled at 45° to the ground and centered on hoof *

*The same placement is used for navicular DP oblique, but tube is angled at 65° to the ground

Dorsopalmar/Dorsoplantar Oblique
Navicular = distal sesamoid bone, located at P2-P3 joint
Lateral view as for pedal bone
Dorsopalmar/Dorsoplantar view as for pedal bone except:
Position x-ray beam at 65 degrees toward the middle of the second phalanx, just ABOVE the coronary band OR
Place hoof into wooden block with wedge that places dorsal wall of the hoof in vertical position
Navicular Bone
Long Pastern Bone = proximal phalanx, P1
Short Pastern Bone = middle phalanx, P2
Lateral View:
centered over middle of pastern or at level of interest
Hoof elevated on wooden block
Cartridge on medial side of hoof, perpendicular to the floor
Proximal Phalanges
Beam center over area of interest
Hoof elevated on wood block but weight-bearing
Cartridge placed behind limb, parallel to phalanges (usually about 45 degrees) and tube is angled so that it is perpendicular to the cassette
Proximal Phalanges/Dorsopalmar/Dorsoplantar
Metacarpal/Metatarsal- phalangeal joint, proximal medial and lateral sesamoid bones
Dorsopalmar/Dorsoplantar
Beam center: through joint at right angle to cassette
Foot placed with full weight on floor and cassette placed directly behind foot, perpendicular to floor
Field of view: entire fetlock joint, distal cannon bone, proximal long pastern bone
Fetlock Joint
Lateral View
Foot should be weight-bearing, directly under body (may need to raise other leg)
Cassette placed on medial side of joint, perpendicular to the floor
Center beam at middle of joint and include entire joint, proximal and distal ends of adjacent bones
Flexed Lateral
Attendant must hold hoof in fully flexed position, using protective gloves and beam must be collimated so that attendant’s hand is not exposed in field of view
Fetlock
Oblique Views: Dorsolateral or Dorsomedial
Allow visualization of medial and lateral sesamoid bones
Angle varies from 30 to 45 degrees medially or laterally from dorsal midline of joint
Cassette should always be positioned perpendicular to the beam
Oblique Views: Dorsoproximal
Angle beam through center of joint with tube 45 degrees proximal
Cassette behind joint, perpendicular to angle of x-ray beam
Fetlock
Cannon Bone (3)and Splint bones (2 and 4)
Dorsopalmar or Dorsoplantar View
Lateral View
Dorso-Lateral and Dorso-Medial Oblique Views
Patient should stand normally, bearing weight on the limb
Cassette placed against opposite aspect of limb, at right angle to beam
Beam centered midpoint of bone, parallel to floor
Include proximal and distal joints
Use 45 degree angles for oblique views
Metacarpus/Metatarsus
Two rows of carpal bones
Radial, ulnar, intermediate and accessory
2nd, 3rd and 4th
Carpus Joint – The Knee
Dorsopalmar
Must be TRUE DPa centered over middle of carpus; Guideline: draw line from center of hoof up to radius
Lateral
Beam centered laterally in middle of carpus joint
Flexed Lateral
Limb elevated and carpus flexed by having assistant hold hoof
DO NOT allow leg to abduct. Maintain carpus directly under the body
Carpus Radiographs- Many Views
Oblique Views
Allow visualization of individual carpal bones depending on direction and angle of beam
Skyline Flexed Views
To view dorsal surface of carpal bones
Lift leg and flex so that metacarpus is parallel to the floor, then place cassette against dorsal surface of metacarpus
Angle beam to get skyline view of proximal row or distal row of carpal bones
Carpal Radiographs
Three rows of tarsal bones
Tarsus Joint – The Hock
Dorsoplantar View
“Toed out”: Rotate limb slightly lateral so tube doesn’t have to be placed under body
DO NOT stand behind the horse
Lift opposite FRONT leg to prevent motion
Lateral View
Beam center over middle tarsal joint, about 4 inches distal to calcaneal tuberosity
Flexed Lateral View
Best view of tibiotarsal joint
Oblique Views
Beam at 45 degree angle medial or lateral from dorsal midline of joint
Tarsal Radiographs
Craniocaudal
Difficult to do standing, but if no other choice…
Pull affected leg as far cranial as possible
Press long edge of cassette against thorax wall at caudal aspect of elbow joint
Try to maintain true craniocaudal by centering olecranon between humeral tuberosities
Medio-Lateral
Affected limb lifted and extended as far forward as possible
Cassette placed against LATERAL side of joint
Elbow Joint
Medial to Lateral view is the only practical view unless animal under general anesthesia
In standing patient, elevate and pull limb cranially, pulling shoulder joint away from the body wall
Palpate to make sure beam centered over joint and include proximal and distal ends of bones
Shoulder Joint
Difficult because of thickness of surrounding tissues; little visualization of femoral region
Sensitive body area; take care to avoid being kicked; use sedation if possible
Caudocranial View
—Cassette against cranial aspect of joint, tilted so long edge rests against body wall
—Lift opposite hind limb for better control
—Center beam over stifle joint, 4 inches distal to patella
Lateral View
—Cassette against medial aspect of joint, gently pushed into flank
—Beam centered over joint, 4 inches distal to patella
Stifle Joint
Must be done under general anesthesia
Requires high powered machine and use of grid because of thickness of area
Ventrodorsal, frogleg view is best
—Dorsal recumbency, hind limbs flexed
—Center cassette under distal pelvis, over area of interest
—May need to expose in two or three sections
—If so, mark beam centers with tape or pen to help make multiple exposures
Pelvis
Remove any halters with metal
Areas of interest: Cranium, Sinuses, Gutteral Pouch/Larynx/Pharynx, Teeth
Lateral view
—Position cassette against affected side
—Avoid head rotation for true lateral
—Center beam over area of interest
Gutteral Pouch Lateral View
—Center beam just caudal to vertical ramus of the mandible
Skull
Dorsoventral view- Gutteral pouch/throat
—Sedation recommended
—Standing position, head lowered as far as possible
—Cassette placed against ventral side of skull under mandible
—X-ray tube positioned over head, beam perpendicular to cassette
—Center beam at midline of skull over area of interest
Skull
Need oblique views to avoid superimposition of opposite arcade
Cassette placed against side of interest
Angle beam 30 degrees down from lateral for best visualization of upper arcade
Angle beam 45 degrees up from lateral for lower arcade
Can do intraoral of maxillary and mandibular incisors
Teeth
Can do lateral cervical spine standing with high powered machine
Need 3 exposures
—Area 1: Centered over C2
—Area 2: Centered over C4
—Area 3: Centered over C5
Remember- Cervical spine runs along ventral portion of neck
Thoracic spine: Can visualize dorsal spinous processes (withers) with lower-powered unit
Can get views of rest of equine spine only with high powered units and grids for density of tissue
The Spine
Additional Areas: Thorax
Four views required
Lateral views in quadrants
Need grids
Increase SID to 80 inches
Additional Areas: Thorax
Series starting cranioventrally and moving caudodorsal
A standing cassette holder with grid is used
Additional Areas: Abdomen
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