506 Canine Sports Medicine and Rehabilitation
lesion detection using direct versus indirect
arthrography appear to be slight, with the
biggest disadvantage being lack of joint disten-
tion using indirect arthrography (Applegate
et al., 1993; Waldt et al., 2007; Jung et al., 2009).
In dogs, direct MR arthrography has been
used for evaluation of the stifle and shoulder
joints. In the shoulder, image quality of the soft
tissue structures within the joint was found to
be enhanced (Vahlensieck et al., 1996). In the
stifle, soft tissue structures were also more
readily identifiable, and in a group of military
working dogs, some pathological changes
were only visible after use of direct contrast
arthrography (Banfield & Morrison, 2000;
Schaefer et al., 2010).
There is significant information in the liter-
ature documenting normal anatomy as well
as pathological findings of musculoskeletal
MRI studies in dogs. While the focus of most
MR studies has been on the joints, there is
increasing interest in imaging soft tissue inju-
ries and reports include those on the gastroc-
nemius, supraspinatus, iliopsoas, and long
digital extensor tendon (Fitch et al., 1997;
Fransson et al., 2005; Murphy et al., 2008;
Lafuente et al., 2009; Stahl et al., 2010). MRI
can be a very useful diagnostic tool for both
soft tissue and bone injury, and MRI should be
considered to evaluate any undiagnosed soft
tissue or joint injury.Ultrasonography
Diagnostic ultrasonography generates an
image through the use of high‐frequency sound
waves that are pulsed through the tissue from
an ultrasound transducer. The images are a
product of wavelength, frequency, and velocity
of the sound waves through the tissue (Caine
et al., 2009; Drost, 2012; Nyland et al., 2014).
These sound waves are reflected back to the
transducer as echoes that are converted to an
electrical signal to produce a gray‐scale image
of the tissue being examined. The image pro-
duced is a real‐time, anatomic picture of the
area where the ultrasonography transducer is
being applied (Figure 20.5).
Acoustic impedance, determined by the
density of the tissue being assessed, is the
reflection characteristic of the tissues through
which the sound waves travel and produces
the echoes. Bone, with high impedance, and
air, with low impedance, are perfect reflectors
of sound waves, with the components of softFigure 20.5 Cross‐sectional images of the right and left triceps tendon. The left tendon has a normal ultrasonographic
appearance. There is significant disruption in the fiber pattern of the right triceps tendon when compared with the left.