Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

30 Small Animal Radiolo g y and Ultrasono graphy
Fig. 2-6 A 12-year-old male
Pekingese with a single acute episode
of collapse. A, In the initial lateral
thoracic radiograph there is an
apparent increase in pulmonary
density. The right diaphragmatic
crus overlaps the cardiac silhouette.
The diaphragm is located at the level
of T11. These findings indicate that
this radiograph was obtained at
expiration. B, A second lateral thoracic
radiograph was obtained. The
right diaphragmatic crus is positioned
more caudally. The size of the
right cranial lung lobe is increased.
The diaphragm is positioned caudally
to the level of T13. The overall
pulmonary density appears normal.
The pulmonary vascular structures
are more clearly defined. Diagnosis:
Normal thorax. The apparent
increase in pulmonary density on A
was due to expiration. This can
mimic pulmonary disease and
obscure pulmonary vascular structures
and can create the appearance
of mild cardiomegaly.
A
B
thorax is mostly air-dense lung, whereas the Cocker Spaniel’s thorax is mostly fat and tissue
density. Overexposure of the radiograph may hide intrapulmonary disease, while
underexposure may mimic the appearance of a pulmonary infiltrate (Fig. 2-7).
Selection of specific kilovolt (peak) (kVp) and milliampere-second (mAs) settings is a
matter of personal preference within the requirements dictated to achieve a diagnostic
radiograph. As a general rule, the highest mA setting, shortest exposure time, and a high
kVp setting are preferred for thoracic radiography. The technique selected depends on
machine capability and the x-ray film and screens used. Exposure time is extremely