Ultrasound is particularly useful in visualising abdominal structures and organs, and can also be used to guide the needle in certain kinds of injection therapies.
Other ultrasound uses include:
- Foetal ultrasounds to assess the health of the foetus during pregnancy
- Bone sonometry, to determine bone fragility
- Ultrasound guided biopsies
- Assessment of gallbladder
- Determining the health of an infant brain, spine, heart and hips
- Ophthalmic ultrasound to visualise ocular structures
- Breast ultrasounds to help assess breast tissue health
- Doppler ultrasound to listen to the foetal heartbeat
- Doppler ultrasound to assess blood flow and other internal structures and organs
- Echocardiogram to view the heart and blood flow
- Examination of internal organs such as the bladder, spleen, liver, thyroid, pancreas, kidneys and other structures.
The technology can help diagnose issues such as blocked or narrowed blood vessels, reduced blood flow to organs, infections, tumours and cysts, congestive heart failure, damage due to heart attack, heart valve issues.
Ultrasound relies on producing, detecting and interpreting sound echoes to build an internal picture
Human hearing operates in the frequency range of 20 hertz to 20,000 hertz (20kHz).
Ultrasound applies to all acoustic energy above these frequencies. Diagnostic sonographic scanners typically operate at a level hundreds of times greater than human limits between 2 to 18 megahertz.
Ultrasound-based diagnostic imaging techniques visualise subcutaneous body structures such as tendons, muscles, joints, vessels and internal organs.
Its reflection technology (echo) registers the pulse reflected at the boundary of two tissues with different acoustic resistance. A sound wave is produced by a piezoelectric transducer encased in a probe, where strong, short electrical pulses from the ultrasound machine make the transducer ring at the desired frequency.
The sound is focused through the transducer shape, a lens in front of the transducer, or a complex set of control pulses from the ultrasound scanner machine itself.
This focusing produces an arc-shaped sound wave from the transducer face which travels into the body and focuses at a desired depth. Human tissues are non-homogeneous responding to ultrasonic waves, and their passage through organs, muscles, fat, skins and other body parts leads to refraction, reflection, scattering and absorption of energy.
An image is created based on how long it took for the signal to be reflected back - and much like bats flying in the dark, the soundwaves create a fluid digital image of the underlying body structures. This is achieved through the probe picking up the reflected waves and a computer working out the relative distances of tissues from these waves, and create a picture.
With two probes it is possible to create three-dimensional images, and to measure fluid flow, including for example, blood.
Ultrasound is very good at showing muscle and soft tissue, and clearly showing solid and fluid-filled spaces. Ultrasound doesn’t work well through bone however, so it is not used to look at the brain.