Ultrasonography

dolphin Ultrasonography is a technique which is widely used in paediatric radiology. The basic principle of ultrasonography can be found in nature, dolphins (and other toothed whales) and bats can produce high pitched clicks. When these clicks hit an object, some of the sound will echo back to the “sender”. By listening to the echo and interpreting the time it took before the echo came back, these animals estimate the distance of the object. (That’s why sonar is also called echolocation: with information from the echoes, these animals can locate an object). bat-sonar

 

The same principle is used by the radiologists the creation of an image from sound is done in three steps – producing a sound wave, receiving echoes, and interpreting those echoes. In medical ultrasonography, a sound wave is typically produced by creating short, strong pulses of sound from a transducer. To make sure the sound is transmitted efficiently into the body a water-based gel is placed between the probe and the patient’s skin. The return of the sound wave to the transducer results in the same process that it took to send the sound wave, just in reverse. In order to produce an image the ultrasound scanner must determine three things from each received echo:

 

 

1.    Which transducer elements received the echo (there are multiple elements on a transducer)

2.    How strong was the echo

3.    How long did it take the echo to be received from when the sound was transmitted

 

 

Once the ultrasound scanner determines these three things, it can locate which pixel in the image to light up and to what brightness.This results in an image of the inside of your child.

As ultrasonography does not use radiation and is extremely patient friendly it is used very often in paediatric radiology.