A shared terminology to describe the movement of the transducer during scanning is important in order to optimize the image.
During the workshop it makes it easier for the supervisor to give instructions without touching the transducer which is crucial for the novice in order to achieve practical skill.
There are many available descriptions of the method of manipulation of the transducer.
We recommend using: 1. rotate (right – clockwise, left – counterclockwise) 2. rock (in-plane motion away or toward the indicator) 3. tilt (angling the transducer – perpendicular to rocking) – sweep (is tilting with a continuous fanning motion back and forth) 4. slide (moving the transducer on the skin)
As a novice you should only manipulate the transducer in one direction at a time.
Figure showing movements in three different spatial directions. Confused? Look at the video in the next topic!
Frequency The frequency of a sound wave is equal to the number of wave tops per time unit.
The SI unit for frequency is Hertz (Hz) = wave tops pr second.
Ok, so that does not sound simple…
This is what you need to know: The longer the distance the sound wave travels, the more energy is lost to absorption.
The ability of a sound wave to penetrate through tissue depends on the frequency of the sound wave – a lower frequency (lower number of wave tops) gives a better penetration.
On the other hand, a higher frequency (more wave tops) causes a higher resolution, but a lower penetration.
Imaging Ultrasonography is an imaging method based on ultrasound.
Ultrasonography uses the impulse-echo principle of generating and emitting short pulses of ultrasound that are reflected at tissue interfaces and subsequently recorded by the receiver.
The reflected sound wave is essential for the production of the ultrasound images.
The illustration shows the emission of sound from the transducer and reflection of the signal at tissue interfaces. The ultrasound waves that hit an interface, here a bone, reflect the ultrasound. The waves that do not hit anything do not generate any echo.
The first look at an ultrasound machine can be an intimidating experience.
You see a bunch of unfamiliar buttons and knobs and confusion sets in. The user manual is often poorly designed, which only adds to the confusion. You turn it on, stare at a screen, and feel lost.
But, it can be made simple and easy, and you can quickly master the machinery through a basic understanding of ultrasound and by using a few controls.
Learn the few essential buttons – On/Off, select transducer, select preset, adjust gain and depth – and you are up and running.
Physics In physics, the word “ultrasound” refers to sound with a frequency the human ear cannot perceive.
Application Ultrasound is used among other things as a sonic depth finder in navigation, for cleansing of sensitive objects (e.g. contact lenses) and in testing non-disruptive materials in order to detect faults and fractures.
In medical diagnostics, ultrasound can be used for visualisation of anatomical structures and for assessment of physiological processes.
The ultrasound used for medical diagnostics is usually between 2 and 18 MHz.
