20/10/2016
How animal ultrasound machine work?
Ultrasonography can be used to examine and evaluate various parts of an animal. It uses the same technology that
is used in human ultrasound examinations. Ultrasound can be used internally (transrectally) or externally (on the
body wall/skin surface).
The ultrasound probe contains crystals with specialized properties –
primarily that they can both create and receive ultrasound waves. These ultrasound waves are able to pass through
some body tissues more easily than others. As an ultrasound wave encounters a tissue, it is either reflected back to
the probe, absorbed by the tissues or refracted (‘scattered’) into neighbouring tissues.
The ultrasound machine is then able to determine how strong the returning wave is and also how long it has taken
for it to return back to the probe. These two factors are therefore mainly responsible for determining the
echogenicity of that tissue on the ultrasound image (how black, white or grey it appears) and also how deep within
the body it is. The stronger a returning wave is from a particular part of the body, the brighter the ultrasound
image will appear for that area. In addition, it will take longer for an ultrasound wave to return from a tissue which
is further away from the probe. Therefore tissues which are deeper in the body are displayed on the ultrasound
image as being further from the probe.
Ultrasound images appear as a mixture of black, white and grey areas. Objects that appear black (anechoic) are
generally some type of fluid. This is because the ultrasound waves pass easily through fluid and therefore there are
none or very few waves reflected back to the probe. As a result, if the machine does not receive information from a
particular region being scanned, it will display this as a black/anechoic area of the ultrasound image. Very dense
areas, such as bone, will appear white on the ultrasound image as the waves are strongly reflected from this type of
tissue back to the probe. Other tissues reflect the waves to varying degrees and therefore these structures (such as
abdominal organs and muscle) appear in varying shades of grey. This process creates an image that enables you to
evaluate differences between various body structures (such as follicles versus the corpus luteum on the bovine
o***y.)
The frequency of the waves being emitted from the probe can have a significant impact on the quality of the
ultrasound image displayed on the monitor. Using a higher frequency setting will generally result in a greater
clarity of the ultrasound image (‘resolution’), however it will not be able to travel to as great a depth as it would
when using a lower frequency setting. Therefore a lower frequency setting enables the waves to pe*****te more
deeply into the tissues, with the resolution of the ultrasound image being less. Therefore, when considering what
frequency setting to use when performing an ultrasound exam, you must always balance the clarity or resolution of
the image with how far/deep you expect the ultrasound wave to travel.
