If you’re like most people, you probably think of ultrasound as a way to get a picture of your baby during pregnancy. But ultrasound can also be used for other things, like checking out your organs or looking for tumours. In fact, ultrasound is a pretty versatile tool that can be used for all kinds of different medical purposes such as guiding joint injections. So what is ultrasound, exactly?

What is ultrasound?

Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from “normal” (audible) sound in its physical properties, except that humans cannot hear it. This limit varies from person to person and is approximately 20 kilohertz (20,000 hertz) in young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz.

There are many different uses for ultrasound. For example, ultrasound can be used:

– To produce images of internal organs for medical diagnosis (medical sonography)
– To monitor the flow of blood and to measure heart function (echocardiography)
– To create images of a developing foetus (obstetric ultrasonography)
– To guide needle placement during biopsies and other procedures (interventional ultrasonography)
– To clean teeth (ultrasonic dental cleaning)
– To break up kidney stones (shock wave lithotripsy)




How ultrasound works

Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from “normal” (audible) sound in its physical properties, except that humans cannot hear it. This limit varies from person to person and is approximately 20 kilohertz (20,000 hertz) in healthy young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz.

How ultrasound works

When ultrasound waves hit an object, they reflect off of it. The time it takes for the waves to bounce back is used to calculate the depth of the object. The waves also change direction when they hit a boundary between two different materials – for example, the tissue interface between muscle and fat – which can be used to produce two-dimensional images.

The benefits of ultrasound

Ultrasound has a number of benefits, both for medical purposes and for other uses.

Some of the medical benefits of ultrasound include:

– Diagnosing problems in unborn babies
– Looking for problems in the heart, liver, kidneys, or other organs
– Guiding doctors during surgery
– Helping to break up kidney stones
– Reducing pain and swelling from injuries
– Treating cancer

Ultrasound can also be used for non-medical purposes, such as:

– Cleaning jewellery and glasses
– Cutting through metal and concrete
– weld outdoor power equipment

Ultrasonic waves are also used in humidifiers and nebulizers.

The risks of ultrasound

While ultrasound is generally considered safe, there are some risks associated with the procedure. One of the risks is that the sound waves could heat up body tissues. This could damage tissue or cause it to swell. These risks are more usually associated with multiple pulsing modes such as Doppler imaging, and high-frame-rate, high-line-density modes. These imaging settings are hardly used when scanning musculoskeletal tissues and if used (colour or power doppler) they are used for very short amounts of time typically less than a minute.

Another risk is that the waves could reflect off of bones or other structures in the body and cause interference in the image. This could make it difficult to get a clear picture of the area being examined.

Ultrasound may also not be recommended for pregnant women or those who are pregnant with twins or more because of the potential risks to the developing foetuses.

How to prepare for ultrasound

Preparation will depend on the type to of ultrasound you are having.

Some ultrasound examinations like musculoskeletal ultrasounds require no preparation when for some other you might have to fast for a few hours or drink water.

 

What to expect during ultrasound

You must expect different experiences depending on the kind of ultrasound you are having but in general you will lie on your back on an examination table. A clear gel will be put on your abdomen. The gel helps the sound waves from the transducer travel through your skin to your internal organs.

The transducer is a handheld device that emits sound waves and picks up the echoes as they bounce off your organs. The echoes are then translated into images on a monitor that the radiologist or sonographer can interpret.

 

After the ultrasound

You should be able to go home soon after the procedure.

 

Further reading

 

If you want to learn more about ultrasound, there are a few good sources of information:

-The Mayo Clinic has a good overview of ultrasound, including what it is, how it works, and what it can be used for.

-The American Institute of Ultrasound in Medicine (AIUM) also has a good general overview of ultrasound.

-If you’re interested in the history of ultrasound, How Stuff Works has a short article on the origins of ultrasound technology.