Introduction to Ultrasound

  • Ultrasound involves the use of sound waves with high frequency that are beyond the range of human hearing.
  • These sound waves typically have a frequency above 20,000 Hertz (Hz), which is the upper limit of human hearing.
  • The technology utilises the echoes made by sound waves to produce images or to detect the presence of certain substances or conditions.

How Ultrasound Works

  • An ultrasound machine produces high-frequency sound waves, which are sent into the body using a probe.
  • The sound waves travel through the body and hit a boundary between tissues (e.g., between fluid and soft tissue, soft tissue and bone).
  • Some of the sound waves get reflected back to the probe, while others carry on until they reach another boundary and get reflected.
  • The reflected waves are picked up by the same probe and relayed to the machine.
  • The machine calculates the distance from the probe to the tissue or organ using the speed of sound in tissue (1540 m/s) and the time of each echo’s return.
  • It then uses this information to produce a two-dimensional image on a screen.

Ultrasound in Medical Science

  • Diagnostic ultrasound, also called sonography, is commonly used in medicine. It produces real-time images of the inside of the body and provides detailed pictures of the body in a safe and non-invasive way.
  • Ultrasound is most famously used in obstetrics, to monitor the growth and development of babies in the womb.
  • It’s also used to detect issues with organs, tissues, and blood vessels, without needing to make an incision.
  • Doppler ultrasound is a special type of ultrasound that creates images of blood flow in vessels.

Advantages and Limitations of Medical Ultrasound

  • Advantages: Ultrasound imaging is non-invasive, does not involve ionising radiation, gives real time imaging and is less expensive compared to other methods like CT scans or MRI.
  • Limitations: Image quality is heavily operator-dependent, it can’t penetrate bone or gas, and it has difficulty imaging structures deep in the body.

Without a clear understanding of how ultrasound works, its various medical applications may seem magical. Yet, it’s simply science – specifically, the science of Medical Physics