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 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…

PALMAR

MEDIALLATERAL

DORSAL

http://www.vetmed.wisc.edu/Dr__Adams_938-675.220.1.html

CT or CAT Scan

Computed tomography has just recently 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 rateof bone development in the distal limb. At this stage the foal mustbe anesthetized for a short time so there is no movement artifact.”

MRI Magnetic Resonance Imaging; the area being

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 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

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

MusculoskeletalPalmar distal extremity

ReproductionUterine cysts

AbdomenLiver - cholelithiasis

Infected umbilicus EchocardiographyPericardial effusion

ThoraxPleuropneumonia

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 location1. Zones2. Reference points

- cm distal to standard pointaccessory carpal bonepoint of hockpoint of ergot

Transverse imagesPalmar (skin surface)

Dorsal

LateralMedial

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

Illumination lens

Instrument channel

Air/Water 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