AN EXAMPLE OF ACOUSTIC SHADOWING

One of the most common causes of acoustic shadowing is bone or calcifications. Whilst this effect can make scanning in late gestation increasingly difficult, acoustic shadows can at times be extremely useful. Often, when performing an abdominal scan, we come across debris in the bladder. When calcified, an acoustic shadow will often be cast behind this debris, where the ultrasound waves are unable to penetrate. This aids the sonographer in their work, as the effect provides information as to what the debris is actually made up of. In this example, one could be sure that they were seeing bladder stones.

We cover incidental findings in more depth on our level two canine ultrasound courses.

Below is an image of a late gestation (approx. 50 days) pregnancy in a labradoodle. Note how the ribs of the puppy stop the penetration of the ultrasound beam, due to the high reflectivity and absorption of bone, in a way that the foetus in early gestation does not. Also note that the acoustic shadow is not seen further down the image, as the ultrasound beam diverges and the parts of the signal not blocked by the bone diverge out and fill in the gaps.