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KS5 Physics
Lesson Plan 4 – Ultrasound
Science at Work in Healthcare
Post – 16 Science Education Pack
Resource Sheet 4.2 – What is Ultrasound?
Ultrasound is simply sound with a frequency greater than the upper limit of human
hearing. This is usually taken to be about 20 kHz.
Uses of Ultrasound
In the last fifty years ultrasound has found a wide variety of uses:

Medical – ultrasound is used widely in medical applications ranging from
diagnostic imaging to cleaning teeth and drug delivery.

Industrial – ultrasound is used for the non-destructive testing (NDT) of all
kinds of materials, from concrete to the latest alloys and composites.

Cleaning – ultrasound is used for cleaning jewellery, lenses, watches and
other delicate objects.

Humidification – ultrasound is used in certain types of humidifiers. A metal
plate is caused to vibrate at ultrasonic frequencies and this vibration causes
water on the plate to nebulise and form a cool mist.

Chemistry – ultrasound can be used to facilitate chemical reactions. It
breaks up solids and can remove oxide layers etc, giving a greater surface
area for the reaction to occur over. It can also cause localised extremes of
temperature and pressure.

Range finding – ultrasound is employed in sonar systems for range finding.
It can also be used for short distances in air, as in car reversing sensors.
Fig. 1 Ultrasound scan of 5 week old embryo
KS5 Physics
Lesson Plan 4 – Ultrasound
Science at Work in Healthcare
Post – 16 Science Education Pack
Medical Ultrasound
For most people, the word ultrasound is most associated with medicine and
particularly fetal ultrasound scans. However, even in medicine ultrasound has a wide
range of different uses. In the NHS, ultrasound is commonly used in the following
areas:

Diagnostic imaging – sonographers or ultrasonographers use ultrasound
scanners to produce high quality images of delicate structures in the body
such as the heart, eyes, kidney and liver, without the risks associated with
ionising radiation. Ultrasound scanners can also make use of the Doppler
Effect to collect information about the speed of blood flow. Ultrasound
scanners generally use sound frequencies between 2 MHz and 18 MHz

Procedure guidance – because of the real time nature of ultrasound scans
they can be used to guide the surgeon during procedures such as biopsies.

Cancer treatment – high intensity focused ultrasound (HIFU) can be used to
treat malignant and benign tumours by causing localised heating of the
tumour. This procedure uses ultrasound in the 250 kHz to 2 MHz range at
high intensities.

Drug delivery – ultrasound can play an important part in the delivery of
chemotherapy to brain cancer cells via a process called Acoustic Targeted
Drug Delivery. Ultrasound of a frequency between 1 MHz and 10 MHz is
focused on the subject tissue at intensities of up to 20 W/cm2. The energy
from the ultrasound agitates the tissue and makes it more permeable to the
chemotherapy drugs.

Lipectomy – ultrasound is used in ultrasound assisted lipectomy (UAL)
where high intensity ultrasound helps to break up fatty tissue before it is
removed by suction.

Elastography – subjecting tissues to low frequency ultrasound can be used
to measure their elasticity. In certain cases differences in elasticity can be
used to discern healthy from unhealthy tissue.

Occupational therapy – high intensity ultrasound can be used to generate
localised heating of tissues, which can be beneficial to certain conditions.

Dentistry – ultrasound can be used for teeth cleaning.