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Acclarix AX3 Series Diagnostic Ultrasound System User Manual Ultrasound Intensity and Safety
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Appendix B Ultrasound Intensity and Safety
B.1 Ultrasound in Medicine
The use of diagnostic ultrasound has proved to be a valuable tool in medical practice. Given its known
benefits for non-invasive investigations and medical diagnosis, including investigation of the human
fetus, the question of clinical safety with regards to ultrasound intensity arises.
There is no easy answer to the question of safety surrounding the use of diagnostic ultrasound
equipment. Application of the ALARA (As Low As Reasonably Achievable) principle serves as a
rule-of-thumb that will help you to get reasonable results with the lowest possible ultrasonic output.
The American Institute of Ultrasound in Medicine (AIUM) states that given its track record of over 25
years of use and no confirmed biological effects on patients or instrument operators, the benefits of
the prudent use of diagnostic ultrasound clearly outweigh any risks.
B.2 Ultrasound Safety and the ALARA Principle
Ultrasound waves dissipate energy in the form of heat and can therefore cause tissue warming.
Although this effect is extremely low with Transcranial Doppler, it is important to know how to control
and limit patient exposure. Major governing bodies in ultrasound have issued statements to the effect
that there are no known adverse effects from the use of diagnostic ultrasound, however, exposure
levels should always be limited to As Low As Reasonably Achievable (the ALARA principle).
Imaging Functions Affecting Acoustic Output
In addition to the level of voltage transmitted, adjustment of the following imaging functions and /or
controls may affect the acoustic output.
Item Affection
Probe Acoustic output will be changed with the change of probe.
Imaging mode
There are different parameters applied in B mode, Color mode, M mode,
and PW mode, so acoustic output will be changed with the change of among
B mode, Color mode, M mode, and PW mode.
Field of view (scan
angle or scan width)
Frame rate may be changed with the change of the scan angle or the scan
width, and the acoustic output will also be changed.
Image depth
Pulse repeated frequency will be changed with the change of the image
depth, and the acoustic output will be changed.
Focus number
Frame rate and focus position will be changed with the change of the focus
number, and acoustic output will also be changed.
Focus position
Acoustic output will be changed with the change of the focus position even
the beam power level and the beam aperture have not been changed.
Freeze When freezing the system, it will stop transmitting ultrasonic wave.
Transmission power
The output of probe will be changed with the change of the transmission
power, and acoustic output will be changed.
Multi-frequency
The character of the wave focus will be changed with the change of the
frequency, and acoustic output will be changed.