Bioeffects And Safety Of Ultrasound Scans - GE Voluson S6 Basic User Manual

Safety

2.10 Bioeffects and Safety of Ultrasound Scans

2.10.1 Prudent Use – ALARA Principle
2.10.2 Bioeffects
2-22
Network Security:
The remote access features enables, after checkout has been performed, network services
like ftp or telnet on the ultrasound system. Therefore, it is advisable to restrict network access
to system for unauthorized personnel. It is strongly recommended to use a firewall to restrict
network access from and to an ultrasound system with the remote access feature installed.
Other precautions like a secure network segment are encouraged.
When ultrasound waves travel through tissue, there is a certain risk for damage. There has
been a lot of research on the impact that high frequency waves can have on different kinds of
tissues under defined conditions and "There is, to date, no evidence that diagnostic ultrasound
has produced any harm to humans – including the developing fetus." (Guidelines for the safe
use of diagnostic ultrasound equipment, Safety Group of the British Medical Ultrasound
Society 2010).
Physiological effects due to ultrasound are generally assumed to be deterministic and only
occur above a certain threshold in contrast to ionizing radiation, which causes effects
accidentally. Thus ultrasound examinations can be held very safe if certain proceedings are
followed. It is therefore recommended to read the following sections and study the cited
literature.
In spite of the relatively low risk of ultrasound scans compared to other imaging techniques,
the operator shall choose the exposure level with caution to minimize the risk of bioeffects.
"A fundamental approach to the safe use of diagnostic ultrasound is to use the lowest output
power and the shortest scan time consistent with acquiring the required diagnostic information.
This is the ALARA principle (i.e. As Low As Reasonably Achievable). It is acknowledged that
in some situations it is reasonable to use higher output or longer examination times than in
others: for example, the risks of missing a fetal anomaly must be weighed against the risk of
harm from potential bioeffects. Consequently, it is essential for operators of ultrasound
scanners to be properly trained and fully informed when making decisions of this nature."
( Guidelines for the safe use of diagnostic ultrasound equipment, Safety Group of the British
Medical Ultrasound Society 2010)
Special care regarding ALARA should be taken with obstetric examinations as any potential
bioeffects are likely to be of greatest significance in the embryo or fetus.
It is strongly recommended to consider ALARA when undertaking ultrasound scans.
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Thermal effects refer to heating of soft tissue and bone
The thermal indices TIs (soft tissue), TIb (bone near focus) and TIc (bone near surface)
were introduced to provide the operator a relative potential for a tissue temperature rise.
According to the Standard for Real-time Display of Thermal and Mechanical Acoustic
Output Indices on Diagnostic Ultrasound Equipment (2004) those thermal indices shall
be displayed by this ultrasound console. It should be noted that a TI of 1 does not
necessarily mean that tissues being scanned will increase in temperature by 1˚C –
almost every scanning situation departs from the assumed model conditions, such as
tissue type, blood perfusion, mode of operation and actual exposure time of the scanned
area. However, the thermal indices provide information regarding the possible increase
Voluson® S6/S8 Basic User Manual
5433669-100 Revision 4