Page 35 - A Practical Guide to Equine Radiography

16 A PRACTICAL GUIDE TO EQUINE RADIOGRAPHY

• In most applications, we are trying to high- joint alignment as much as possible. Some
VetBooks.ir light small details that require the X-ray beam horses’ conformation requires the adjust-

to be orientated tangential to the lesion, e.g.
ment of the X-ray beam to their individual
highlighting osteophytes at articular margins
or subchondral bone changes. To avoid miss- leg alignment.
ing small lesions we use four projections as
standard in the horse’s leg; in the case of the Post-processing artefacts
foot even more. This inevitably means the Post-processing artefacts are often system-
X-ray beam hits the bone at a degree other specific but include ‘overzealous’ edge enhance-
than 90 degrees resulting in distortion. ment or noise reduction, which may lead to
• While we often manage to keep the X-ray misinterpretation of trabecular pattern; again,
beam at 90 degrees to the X-ray plate, this can it is a good idea to discuss this with the vendor’s
be compromised, e.g. in a lateromedial stifle applications technician. Different practices
this can sometimes not be achieved or in the have different requirements, e.g. a practice that
case where we acquire an upright pedal bone primarily radiographs racehorses will want to
view with the leg standing on a tunnel block. put more emphasis on visualization of changes
• Image distortion is also caused by subopti- in bone density and trabecular pattern, which
mal centring. In the horse, we usually try to requires ‘harder’ images with more bone detail
‘shoot’ through joint spaces and if we do not and less soft tissue. Whereas a practice that
manage to align the direction of the beam deals with general riding horses may be more
with the slope of the joint, the joint space interested in visualizing signs of osteoarthritis,
will be obscured due to superimposition. such as joint effusion and periarticular osteo-
• For many applications we use a horizontal phytes which require ‘softer images’ with good
beam in horses, which will work for horizon- detail of joint margins.
tally orientated joints. Only the central beam
is truly horizontal while the other compo-
nents of an X-ray beam diverge in a cone Other artefacts
shape from that. If the beam is not directly Some of the most annoying artefacts are on
centred on the joint, this divergence will the horse and often relatively easy to avoid,
result in superimposition of the surrounding for example dirt on the skin or solar surface
structures on the joint space. can mimic lesions. A good wire brush is very
• Some joints are naturally sloped (e.g. the helpful to clean the hoof. In heavily feathered
distal intertarsal and tarsometatarsal joints horses, feathers and the air between them can
slope from lateroproximal to distomedial) obscure lesions. We have found wetting them
and the beam has to be adjusted accordingly. down smoothly or using a rubber band to keep
• It is vital to have the horse standing square them away beneficial.
and equally weight-bearing to standardize

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