142 Clinical Features
Figure 20.1 Positioning of a dog for stifle CT scanning:
ventral recumbency with both stifles extended and
scanned simultaneously.
Technical aspects
Positioning
Under general anesthesia, the dogs are scanned
in ventral recumbency with both stifles
extended and scanned simultaneously. Care
should be taken to position them symmetrically
(Figure 20.1).
Technical parameters
With single-slice CT, the X-ray beam is angled
parallel to the surface of the tibial plateau; the
scan range should cover the whole joint, from
the proximal pouches from the distal third of the
femur to the proximal fifth of the length of the
tibia (Figure 20.2).
Multi-slice CT with isotropic resolution
allows scanning of the stifle without tilting
the gantry; angulation and orientation are
performed during post-processing procedures.
In multi-slice CT the slice thickness should
be as thin as possible, 1.25 mm or thinner,
with a slice increment of 50%. In single-slice
devices the suspected pathology dictates the
thickness, which can vary between 2 and 3 mm.
Settings should be 100–120 kV and 100–200 mA,
depending on the animal’s weight and size.
Figure 20.2 Scout view of a stifle CT scan: transversal
scans are made parallel to the joint space. The slice
thickness varies between 1 mm in the joint space and
2 mm at the level of the distal femur and proximal tibia.Sagittal and dorsal reconstructions are made
afterwards. The images are displayed by adjust-
ing window width (WW) and window level
(WL) and read in both a bone window (WW
3500; WL 500) and a soft-tissue window (WW
400; WL 65).The use of contrast medium
Intravenous (IV) administration of 2 ml of
iodine contrast (400 mg iodine ml–1) medium
per kilogram body weight should be used for
any stifle problem involving soft tissues; images
with contrast enhancement provide most infor-
mation regarding the pathology.
Intra-articular (IA) administration of a
diluted non-ionic, low-osmolar-type contrast
medium, such as iohexol, has been reported
to help with distinguishing the cruciate liga-
ments, evaluating the menisci and the surface
of the cartilage (Sungyoung Hanet al. 2008)
(Figure 20.3A,B). The use of computed tomo-
graphic arthrography (CTA) has been described
(Samii 2004), and although the results for CTA
in identifying simulated meniscal injury are