Ultrasound

What is ultrasound?

Ultrasound (or ultrasonography) refers to the use of high frequency audio waves to create images of the tissues & organs within the body. It does not use harmful ionising radiation (like x-rays & CT), provides a live image in realtime, and can give information about the flow of blood through vessels.

How does it work?

Ultrasound works on the principle that sound waves echo & reflect off tissue. Different tissues have different densities and therefore different echo characteristics. The handheld ultrasound probe or transducer sends out high frequency sound waves and receives the reflected echoes. The ultrasound machine is able to interpret these reflected sound waves and create an image from them.

The sound waves used cannot be heard because they are at a frequency above the average human's hearing range. A water-based gel is applied over the skin to help the transduction of the sound waves.

How is it used?

This image shows an ultrasound guided injection of a shoulder, including the needle (blue arrow) and the shoulder joint capsule (white arrow).

There are a number of ways in which ultrasounds are used in medical practice. They are commonly used diagnostically - that is, to image the internal organs of the body, aiding clinicians to see what is going & evaluate symptoms. Some of the more common diagnostic uses of ultrasound are in obstretrics (where ultrasound is used to assess the health and viability of the fetus), in gynaecology (where it is used to identify breast or uterine lesions), and in musculoskeletal medicine (where it is used to identify tears within a joint capsule).

This Doppler ultrasound shows the flow of blood through the common carotid artery as it branches.

Doppler ultrasound is special type of ultrasound that utilises the Doppler effect to present a graphical representation of the speed and direction of flow (usually of blood). It is used extensively to identify narrowing of the blood vessels (eg. of the heart), as well blockages or clots and to identify congenital vascular malformations.

Ultrasounds can also be used to offer real-time imaging guidance for various procedures. These include ultrasound-guided fine needle aspiration (where a needle is used to aspirate a sample of fluid for testing), biopsies (similar to fine needle aspiration, but aspirating a sample of tissue) and injections (to ensure the correct location for injection). Some example images are shown above.

A central venous catheter placed in the neck. This particular catheter has three lumens which serve different purposes.

Vascular access is another area in which ultrasound (and sometimes radioscopic) guidance is commonly used. An example of this is the central venous line (sometimes called a Hickman line). These special intravenous (IV) lines are placed in the heart via a vein in the neck. They can be used for long term IV access for the administration of drugs & fluids, or for dialysis, to obtain blood for certain investigations and to obtain cardiovascular measurements such as the central venous pressure. If long term IV blood products need to be given, a implantable port may be inserted. Line/port insertion is a relatively simple procedure, lasting up to an hour and requiring only light sedation and local anaesthetic. Ultrasound is used to ensure the catheter is inserted in the right vein, and to prevent complications such as puncturing the lungs (pneumothorax) or an artery.

What services does VIRC provide?

VIRC provides ultrasound services at our Subiaco and Midland centres. We specialise in a variety of ultrasound services including both diagnostic and interventional procedures. These include:

• Obstetric
• Gynaecological (breast, pelvic)
• General abdominal
• Musculoskeletal (including US guided injections)
• Fine needle aspirations & biopsies
• Delicate structures (testes, thyroid, opthalmic)
• Vascular (both arterial & venous)
• Line insertions