How is ultrasound used to view an unborn baby?
In: Technology
Using sound waves is like bouncing a rubber ball against the pavement or against the grass. The rubber ball will bounce differently depending on what it bounces off.
It sends sound waves at a particular frequency — sound waves travel through objects, that’s why you can hear from a different room, etc. — and they bounce off things that have particular densities, so you can see what they hit.
Kind of like if you sprayed some liquid with harmless glow-in-the-dark stuff in it, at a doll, in a dark room. You couldn’t see the doll before you started spraying, but you’d see the doll when the liquid hit it, if that makes sense. It’s not exactly the same but
Ultrasound is a sound wave with a very high frequency that humans cannot hear. These frequencies can travel through the soft tissues and fluids, and echo back once they get to a denser object and cannot travel any further.
So far the explanations have mentioned the first half of the process: emitting high-frequency (“ultrasound”) waves and using receivers to detect the returning super-acoustic “echo” waves.
The other half of the explanation: how do the sound “echo” signals actually get reconstructed into a picture? The pixels in the picture are each calculated using math, based on the principles of the *Fourier Transform*.
In its most basic form, that math is more familiar to us in audio processing, to convert data of amplitude and phase, into an audio waveform.
In ultrasound imaging, various math techniques are used, to push for image detail, absence of image artifacts, and fast image reconstruction. 3-D image reconstructions need way more computer processing than 2-D images.
Imagine you had light coming out of your eyes. It would light things up like a light bulb, then bounce off things, come back to your eyes and you can see what’s out there.
Ultrasound is like that, but instead of light waves, sound waves.
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