Principles of Physics in Ultrasound
Physics has become an important part of medicine allowing specialist
doctors and radiographers to rapidly access a patient’s condition and
to help in long-term diagnosis.
This enables doctor’s to treat patients before their condition
This procedure would not be possible without the use of X-rays, CAT
scans, MRI scans, ultrasound and endoscopes, which allow doctors to
see inside the body with little or no surgery.
Without such equipment doctors would be forced to use invasive
techniques, which could cause patients more harm as it increases the
risk of infection.
A sound or ultrasound wave consists of a mechanical disturbance of a
medium (gas, liquid or solid) which passes through the medium at a
Sound waves consist of a disturbance of air molecules, the vibrations
which pass from molecule to molecules from the speaker to the ear of
The rate at which particles in the medium vibrate in the disturbance
is the frequency or pitch of the sound measured in hertz
As the pitch increases there comes a frequency at about 20kHz when the
sound is no longer audible and above the frequency disturbance, this
is know as ultrasound.
The first major breakthrough in the evolution of high frequency
echo-sounding techniques came when the piezo-electric effect in
certain crystals was discovered by Pierre and Jacques Curie in Paris
The turn of the century saw the invention of the Diode (component that
restricts the direction of movement, allows an electric current to
flow in one direction) and the Triode (type of vacuum tube), allowing
powerful electronic amplification necessary for developments in
The early work in the 20th century used ultrasound as a therapy tool
and it was not until the 1940’s that research began into its use as a
The use of ultrasound in medicine began during and shortly after the
2nd World War in various centres around the world. (NSC, UK national
The work of Dr.Karl Theodore Dussik in Austria in 1942 on transmission
ultrasound investigation of the brain provided the first published
work on medical ultrasonic’s.
Although other workers in the USA, Japan and Europe have also been
cited as pioneers, the work of Professor Ian Donald and his colleagues
in Glasgow, in the mid 1950s, did much to facilitate the development
of practical technology and applications.
This lead to the wider use of ultrasound in medical practice in the
Rapid technological advances in electronics and piezoelectric
materials provided further improvements from energy to greyscale
images, and from still images to real-time moving images. The
technical advances at this...