Want that “University-quality” look for thorax and abdominal rads? Make sure your lateral views are straight.Written on September 24, 2013 by Mason Holland, VMD, DACVR Hospital: Port City Veterinary Referral Hospital

We know that careful positioning of abdominal and thoracic radiographs improves diagnostic accuracy. Our brains are wired to readily recognize bilateral symmetry and therefore, identifying straight positioning on VD view of the thorax or abdomen is usually pretty straightforward. How about the lateral views? Can you tell if your patient is lying flat or obliquely on the X-ray table? A crooked lateral view is more difficult to recognize but is a major contributor to low radiographic quality. It prevents obtaining that crisp “University-quality” image that we’d all like to produce and that we would be much more comfortable sending along to a referral center or radiologist.

The key to recognizing a straight lateral view is to look at the vertebrae and, for the thorax, the part of the ribs close to the spine.

In the crooked lateral thoracic view below (Fig. 1), the patient is laying obliquely on the X-ray table, not flat on their side. Look at the dorsal portion of the ribs, one set is projected dorsally and the other is projected ventrally (Fig. 2).  The ventrally projected spine and one set of ribs are superimposed on the dorsal lungs, limiting evaluation. This also gives the impression that the thorax is shorter dorso-ventrally than it really is, which can give an impression that the heart is taking up more of the thorax than normal (false cardiomegaly).

For a larger, sharper view of the radiographs, click the image below.

1fig1-2-vert

In figure 3, the same patient has been placed straight on their side. The dorsal parts of the ribs are now superimposed on each other (Fig. 4). We can now fully evaluate the dorsal lungs, and any impression of cardiomegaly is lessened. The radiograph no longer has the low-quality look from figure 1 and has that nice, crisp anatomy you remember from school.  On that image, I would have liked to see the shoulder extended a little more to get that forelimb out of the cranial thorax, ideally.

For a larger, sharper view of the radiographs, click the image below.

Figures 3 - 4

The Abdomen

For the abdomen, look at the transverse processes of the lumbar vertebrae instead of the dorsal ribs. The transverse processes are long lateral protuberances from the lumbar vertebrae (Fig. 5) and should be superimposed on each other if the patient is lying flat and straight.

fig5

 

In figure 6, the crooked positioning superimposes vertebrae and paraspinal muscles on the abdomen, making it difficult to delineate the dorsal abdominal structures. You can see how not-superimposed the transverse processes are in figure 7. For figure 8, the same patient has been properly positioned and each pair of transverse processes is well-superimposed. We now have a clean demarcation between abdomen and spine and can see a nice plane of normal retroperitoneal fat and better assess the dorsal portion of the abdomen.

For a larger, sharper view of the radiographs, click the image below.

fig6-8-vert

If your goal is to assess the spine, straight lateral views are vital. These same techniques apply for positioning of spinal rads, just alter the centering and collimation.

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