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Diagnostic Techniques for the Equine
What is a diagnostic technique?
▪ A diagnostic technique is a procedure
followed in making a medical diagnosis
Recent advances
The new imaging techniques can replace the physical examination
But each technique may provide additional information
Improved diagnostic capabilities allow earlier surgical intervention
when necessary
This in turn improves survival rates and economic aspects
Non-invasive Diagnostic Procedures
Non-invasive equine diagnostic techniques
include: Thermography Ultrasound MRI – Magnetic Resonance Imaging X-ray CT Scan
Invasive Diagnostic Procedures
Endoscopy
Gastroscopy
Nerve Blocking (subcutaneous, intra-articular including
spine and sacroiliac joint)
Nuclear Scintigraphy
Arthroscopy
Thermography
Infra red rays are given off by body heat and can be recorded
and a picture produced (thermograph)
Inflamed areas are warmer than normal and will show up in
colour on the screen of thermogram
Can pinpoint sites of trauma that cannot be clinically diagnosed
or isolated by nerve blocks
Thermography
Ultrasound
Used for examining soft tissue, particularly tendons and ligaments, but also many
other structures including joints and even eyes.
Sound waves leave the transducer and enter the body, where they reflect off the
bone and soft tissue to produce an echo that is analysed by a computer in the
ultrasound machine and transformed into moving pictures of the organ or tissue
that is being examined.
Bone, which is dense, is identified on screen as a bright line, whereas
a tendon appears as a dotted pattern.
Ultrasound
Ultrasound images are real-time, so unlike X-rays, where you can
only see a static image, with ultrasound movement can be seen
Ultrasound cannot be used
to examine the deeper structures
in bone as bone matter is too dense
CSU-Cvmbs.Colostate.edu
Ultrasound
Ultrasound can also be used to view bone surfaces
Looking for the presence of fractures and infected bone
During assessments detailed measurements are taken
Then during the rehabilitation period the degree of healing can be
assessed
Comparing the initial measurements to the current scan at each recheck
MRI – Magnetic Resonance Imaging
Uses powerful magnetic field instead of radiation to create images
No lead aprons are required
Images are in black and white take only a couple of minutes to generate
Images can be viewed dorsally (top of horse)
Transversely (horizontal cross section)
Sagittally (Vertical cross section)
MRI – Magnetic Resonance Imaging
How it works-
The body is composed mainly of water, so there are loads of hydrogen protons
These protons behave like tiny magnets each with their own magnetic field
Body part being examined is placed in the centre of a strong magnetic field
This causes the hydrogen protons to align
MRI – Magnetic Resonance Imaging
Radio waves are fired into the area
The protons release energy in the form of radio waves which are detected by a receiver coil
Can expose all internal structures together
That is tendons, ligaments, bone etc
Get a whole picture
Best for foot lameness and evaluating fetlock, upper cannon region, knee, hock and the
horses head
MRI – Magnetic Resonance Imaging
MRI is expensive
Is only used when diagnosis cannot be reached using
standard imaging techniques – radiography and
ultrasound
MRI – Magnetic Resonance Imaging
X-Ray – Digital Radiography
There are two forms:
Computerised
Direct capture
Both result in the production of an image on a computer screen
X-rays are acquired using a conventional x-ray machine they use special imaging
plates
With computed radiography a machine called a reader extracts information from the
imaging plate
X-Ray – Digital Radiography
The image is displayed as a digital image on a
computer screen
Currently on large sized imaging plates are only
available
Therefore direct digital radiography is limited to use on
limbs
X-Ray – Digital Radiography
Possible for vets to send electronically images for a second opinion
A proper investigation will require a minimum of four images per joint
Direct digital radiography is quicker than computerised radiography
But capital costs of equipment are greater
Computer for direct digital radiography is linked by cable to the detection plate
– risk of equipment damage
X-Ray – Digital Radiography
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CT Scan – Computed Tomography
An imaging technique that uses a rotating x-ray machine and a
computer to create cross-sectional slices through the body
Generates multiple images of the body
Only available in a small number of veterinary hospitals in the UK
The CT scanner is particularly useful for investigating and diagnosing
dental diseases as well as conditions affecting the sinuses, brain and
skull also taking images of the lower leg.
CT Scan – Computed Tomography
Images are clearer than the traditional x-ray machine allowing more
accurate diagnosis
Only the head can be scanned whilst horse is standing
In order to scan a standing animal, the horse is sedated and stands on a
moving platform that moves the head through the doughnut-shaped
scanner
All other areas to be scanned require general anaesthetic
CT Scan – Computed Tomography
Bone is shown in great detail but MRI is better at
visualising soft tissue
CT Scan – Computed Tomography
Endoscopy
One of the most important special diagnostic tool
Been used by equine practitioners since 1970
It is a flexible telescope with an attached video camera
This is used to visualise internal organ systems while the horse
is sedated
Endoscopy
Widely employed to investigate the respiratory system of
the horse
This is where functional disorders frequently occur in the
upper airway
Gastroscopy involves passing the endoscope down the
esophagus to the stomach.
Reasons to use Endoscopy
Choking up or tongue swallowing or dorsal displacement of
the soft palate (DDSP) Most commonly in race horses
Thought to be related to a disruption in the anatomical relationship between
larynx and soft palate
Exercise induced pulmonary haemorrhage
(EIPH) Occurs in the lungs as a consequence of moderate to strenuous exercise
Related to mechanical stress in the lungs which occurs with forceful breathing
Dynamic Endoscopy
Dynamic endoscopy allows the clinician to examine the upper airway of the horse whilst it is
exercising
Dynamic obstructions of the equine upper respiratory tract may be undiagnosed when resting
endoscopic examination is performed
Two methods to examine upper airways during exercise
Treadmill
Overground endoscopy
Dynamic endoscopy on a high speed treadmill provides a far better assessment
Treadmill endoscopy is available in limited facilities
Dynamic Endoscopy
Overground endoscopy are able to carry out
assessments repeatedly from one day to another
without delay and transportation to treadmill centre
Its safer for both horse and personnel
Should be performed with an experienced rider
Dynamic endoscopy
Overground Endoscopy
Treadmill Endoscopy
Nerve Blocking Nerve and joint blocks involve the injection of a local anaesthetic either close to a nerve or directly into
a joint or into another synovial cavity.
These blocks are used as one part of an examination of the lame horse used to isolate a source of
pain
The local anaesthetic temporarily disrupts the function of any nerves or nerve endings it contacts. This
results in areas of desensitisation (numbing). The desensitised area depends on which nerves or
nerve endings are affected
Typically the blocks are started at the lowest points, working up the limb to isolate the area of pain
Nerve Blocking
Nuclear Scintigraphy
Involves injecting a horse with radioactive dye
Usually a substance called technetium
It’s this that shows up on the scan
Maker can be linked to a number of different tissue
seeking molecules
Nuclear Scintigraphy
Technetium – MDP is attracted to bone
Normal bone has a slow replacement rate
But areas of damage and disease will have an
increased rate of turnover
Will show up as hot spots and red areas on a scan
Nuclear Scintigraphy
Can image areas such as back, pelvis and head areas
A sensitive method of demonstrating bone injuries in horses e.g. Stress
fractures
Does not give any information on cartilage, ligaments or tendons
Strict radiation protection must be followed
Equine patient must be isolated after having scintigraphy performed
Nuclear Scintigraphy
Arthroscopy
Is routine procedure in human medicine – keyhole surgery
The keyhole technique by which surgery is performed on equine joints for
traumatic injury, fractures within joints, soft tissue injury, and abnormal joint
development in young horses, such as osteochondritis dissecans (OCD).
A small telescope can be inserted into the joint
Powerful source of light is transmitted down the arthroscope
Allows visualisation of joint interior
Arthroscopy
Small instruments are then inserted into the distended joint
There are a variety of attachments – usually between 2 – 4.5 mm in diameter
Capable of removing areas of damaged cartilage, membrane and bone
Arthroscopy