What is an ultrasound scan?

Also known as sonography (or diagnostic medical sonography), an ultrasound scan is a medical diagnostic tool which makes use of high-frequency sound waves (similar to sonar or radar which are used to detect military planes or ships) to capture live images of the inside of the body’s structures (i.e. a sonogram).

Images generated by this medical test allow doctors the ability to see and determine abnormalities or health-related problems with the body’s tissues, vessels and organs. Generally, an ultrasound examination involves the use of a sonar device applied to the outside of the body (although on occasion some techniques place the device inside the body for examination, for example during gynaecological visits). The techniques used are generally non-invasive and pain free, not requiring incisions (cuts) to be made into the body, and effectively assist doctors in being able to diagnose and treat a variety of different health conditions and diseases.

This type of imaging technique also does not make use of any radiation (using sound waves instead), making it a preferred medical test for many health conditions, most notably the viewing and monitoring of a developing foetus (unborn baby) throughout pregnancy.

How does ultrasound imaging work?

A transducer (a wand-like hand-held device) is used to emit high-frequency sound waves and record echoes of the inside of the body. The device is placed on the surface of a patient’s skin in the area to be examined. Sound waves travel through fluids (such as blood) and soft tissues, and bounce off of (reflect back) denser surfaces or structures (i.e. more solid tissues such as a heart valve or chamber), recording echoes. Sound waves will pass through soft tissue structures and fluids if there are no obstructions or dense tissues in their path. Once sound waves connect with dense tissue, echoes bounce back and create an image. The denser the tissue is, the more sounds waves will be bounced back.

The recorded echoes (sound waves) produce an image in real time, and help a medical professional to see the size, shape and consistency of organs, structures (muscles, tendons or joints) and soft tissues on a monitor or computer screen. The image produced displays varying shades of grey due to the different strengths of reflected back echoes which essentially reflect the different densities of tissue recorded (. The sound waves and echoes emitted and reflected in this type of scan have an ultrasonic frequency which is inaudible to human ears, hence the name ‘ultrasound’.

Sound wave frequency for diagnostic purposes is normally between 2 and 18 megahertz (MHz). A doctor may use a higher frequency to obtain a better-quality visual. A lower frequency, however can penetrate much deeper into the body, but cannot achieve a high-quality image.

Medical professionals, including ultrasound technicians or sonographers and specialists, receive qualified training in order to perform such an examination. Doctors and radiologists are also specially trained in order to interpret the results of the images created.

Ultrasound scans are a useful technological tool for monitoring the development of an unborn baby (foetus) during pregnancy, diagnosing a medical condition or assisting a medical doctor or surgeon while performing other procedures, such as during fertility treatments (egg harvesting or retrieval) or certain types of biopsy (when a sample of tissue is extracted from the body in order to be analysed, examined and tested).