Diagnostic Imaging of
Horses
LACP
Chapter 7
Pages 147-175
Diagnostic Radiology
 Very similar to small animals
 Principles are the same as in small animals
 Large animal radiology is very unique due to the
conformation of the patient and the fact that
most radiographs are performed on a standing,
awake patient.
 The temperament of the animal can hinder the
ability to position a patient for ideal film studies.
Safety: “Fear Factors”
 Injured horses-painful
 Strange noises
 Strange things touching the horses; for
example, ideally the film cassette should
be placed to contact the patient’s skin.
 Personnel and equipment are in
vulnerable positions with a patient that is
often suspicious of the situation.
Safety: Personnel Involved
 Move slowly and speak in a low calm
voice
 Do not make loud crashing noises
 Let the horse know that you are getting
ready to do something to him/her. Gently
rub the area of interest-touch it lightly if it
is not injured.
 PPE-Wear these items! What are they?
Just how many people does it
take to take a radiograph?
 One person to tend to the horse’s head-
your restrainer
 One person to operate the radiograph
machine
 One person to hold/position the film
cassette
 That’s right-this equals 3
Anatomic Direction
• Femur tibia/fibula
– Cranial - Caudal
• Tarsus - digits
– Dorsal Plantar
The five Routine views
 Lateromedial (Lateral)--Extended
 Lateromedial (Flexed lateral)--Flexed
 Dorsopalmar (DP)
 Dorsolateral-palmaromedial oblique (DLPMO)
 Dorsomedial-palmarolateral oblique (DMPLO)
Radiograph labeling
 Standard convention
 Marker is placed
 Cranial / Dorsal
 Lateral
 Be sure to “flash” the cassette
 Permanently identifies film as belonging to a
certain patient
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Owners name
Patient name / number
Name of clinic / Location
Date of exam
Limb examined (RF, LF, RH, LH)
The Equipment:
 Radiograph machine
 Caliper
 Radiograph cassette holder
 Cassette/film
 Play-doh or putty
 Positioning blocks
 Processor to develop the film
 Chemical Sedation/Restraint devices
 PPE
 Time and patience!
Radiograph Cassette holder
Film cassette in cassette holder
Portable radiograph machine
Portable radiograph machine
Portable radiograph machine
with a light collimator
Wood and Plexiglas positioning
block for the equine foot.
Position of the cassette for
stand-on radiographic views
Position of the foot and cassette
for stand-on views of the foot.
Slots provide additional
support for film cassettes.
Packing of the grooves of the
sole to prevent artifacts
created by the air pockets of
the hoof.
These artifacts can
sometimes mimic fracture
lines and may obscure true
lesions. Do not over pack.
Always be sure to clean the
hoof wall, sole and recesses
of the frog.
Hoof picks, soap, water and a
brush may be needed.
Here’s the setup! Without the
horse of course…
Generally you are about 30-40 inches (80 cm.)
away from the patient.
Removal of the shoe is recommended but is
expensive to remove and place back on the
horse. Many owners will object to this. Always
obtain owner consent before removing shoes!
Horseshoes interfere with
interpretation of radiographs
Hoof anatomy
Lateral
• Horse is weight
bearing
• Cassette holder is
used
• X-ray beam is
perpendicular to
the middle carpal
joint
Flexed Lateral
• Foot is elevated
• Carpus held in flexion
• X-ray beam is centered
at middle carpal joint
• Tendency to shift
carpus toward midline
• Hands are close
enough for scatter
radiation--use gloves!
Dorsopalmar
• Weight bearing
• X-ray beam
centered at
middle carpal
joint
• Cassette parallel
to the palmar
aspect of the limb
DLPMO
• Weight bearing
• Foot of interest
placed slightly
cranial
• Centered at middle
carpal joint
• Beam is 60 degrees
lateral off a straight
dorsal-palmar
DMPLO
• Same as previous,
BUT, beam comes
from 60° MEDIAL
from a straight DP
• Since beam comes
across the front of
the horse, have a
cooperative horse
Sedation if needed
A Review…
DORSAL
LATERAL
MEDIAL
PALMAR
 http://www.vetmed.wisc.edu/Dr__Adams
_938-675.220.1.html
CT or CAT Scan
 Computed tomography has just recently
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become available for large animal patients.
This equipment is very expensive and limited to
specialized facilities.
Use is restricted in adult horses to the
examination of the head, cranial cervical spine
and distal limbs.
Patient must be under anesthesia.
Must be injected with radioisotope and is
absorbed by bony areas
Used as a last resort in diagnosing.
CT scan of the horse’s nasal passages
This is the CT control room. The animal patient must be
anesthetized because you can not remain in the room with them.
There can be no motion or movement involved.
“By scanning foals as they mature, one is able to directly quantify the rate
of bone development in the distal limb. At this stage the foal must
be anesthetized for a short time so there is no movement artifact.”
MRI
 Magnetic Resonance Imaging; the area being
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imaged is placed within a strong magnetic field
and stimulated by radio-frequency pulses.
These radio-frequency signals are collected
and analyzed by computers to form the image.
Very, very costly and not widely available
Anesthesia is required
MRI tend to be superior to CT for soft tissue
imaging
The head, cervical spinal cord and lower legs
can be imaged in an adult animal
Precise and focal imaging tool that produces
images of all tissue types; bone, tendons,
ligaments, and fluid. Mainly utilized in equine
lameness.
Thermography
 Uses a heat camera to scan the body
surface temperature of the patient.
 Very popular because it is non-invasive,
equipment is affordable and portable.
 Primarily used to locate “hot spots”
which may indicate inflammation near
the body surface. Deeper locations can
not be detected, such as within the
thorax or abdomen.
Stifles: the right stifle shows a “hot spot”
over the medial femorotibial joint.
IR PROx Thermal Infrared Camera
Ultrasound
 Operates on high frequency sound
waves beyond our hearing.
 Uses sound waves to detect differences
in tissue density
 Generally superior to standard
radiographs for visualizing soft tissues.
 Radiographs are superior for imaging
bony structures.
Common uses of Ultrasound
 Visualize kidneys and capable of ultrasound guided
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biopsy
Lungs for pneumonia diagnosis and treatment
GI for colics - small intestinal distension, large colon
wall thickness, peritoneal fluid, diagnosis of abcesses
and tumors
Foals - GI disease, umbilical structures (diagnose
umbilical infections), ruptured bladder
Liver - ultrasound guided biopsy
Assist with lameness diagnosis, including the extent
of tendon and ligament damage
Eyes
Common uses of Ultrasound
cont…
 Monitor the mare's reproductive tract and
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optimize the time for breeding
The genital tract in stallions
Early detection of pregnancy
Early detection of problem pregnancies,
including fetal abnormalities
Cardiovascular
Ultrasound can be used to image the heart,
lungs, kidneys, liver, spleen, and intestines,
even during colic episodes.
Portable veterinary ultrasound
Brief Introduction to Ultrasound
• Transducer produces sound waves and also
receives reflected sound waves.
• Sound waves travel in a plane through tissue.
• Sound waves are transmitted, absorbed or
reflected by tissues.
• Computer forms image – in shades of gray.
• Bone appears white, fluids appear black
From: Zagzebski, JA; Essentials of Ultrasound
Physics, Mosby, © 1996
Musculoskeletal
Palmar distal extremity
Infected umbilicus
Reproduction
Uterine cysts
Echocardiography
Pericardial effusion
Abdomen
Liver - cholelithiasis
Thorax
Pleuropneumonia
Patient Preparation
Clip the area
Clean area
Coupling medium
alcohol
commercial gel
Imaging technique
Systematic organized approach – must be familiar
with normal
Scan from proximal to distal
Evaluate structures individually
Transducer perpendicular to structure
Limb should be weight bearing
Imaging Techniques
Label images - patient info, directions and
location
Two methods for location
1. Zones
2. Reference points
- cm distal to standard point
accessory carpal bone
point of hock
point of ergot
Transverse images
Palmar (skin surface)
Lateral
Medial
Dorsal
Rectal
ultrasound
examination of
a fetus
A 16-day
pregnancy,
visualized rectally
with a 5-mHz
probe.
Video..
Endoscopy
Endoscopy
 Endoscopes come in two basic varieties;
rigid and flexible.
 A thin tube that contains a fiberoptic
camera and a tool at the end allowing
samples to be taken from various
locations in the body. It is passed
through virtually any open cavity on the
body.
 Usually takes 2-3 people to operate
Control handpieces
Air/Water channel
Illumination lens
Instrument channel
Viewing lens
Illumination lens
Control handpiece and insertion
tube of the flexible endoscope.
Endoscope examination of the male urethra.
Notice how many people are involved.
Maintenance of the Equipment
 You will be utilizing some if not all of the
previously mentioned equipment.
 Take care of the equipment and it will
take care of you in the long run.
 Please follow ALL procedures in your
hospital/clinical pertaining maintenance
and trouble shooting equipment.
 Follow ALL cleaning procedures as well.
Read, read, and read! Ask questions!
The End