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| Please find below information issued
by the British Medical Ultrasound Society on the subject of Ultrasound
Safety. |
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| Statement on
the Safe Use, and Potential Hazards of Diagnostic Ultrasound Prepared by the
Safety Group of the British Medical Ultrasound Society |
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Ultrasound is now accepted as
being of considerable diagnostic value. There is no evidence that diagnostic
ultrasound has produced any harm to patients in the four decades that it has
been in use. However, the acoustic output of modern equipment is generally much
greater than that of the early equipment and, in view of the continuing
progress in equipment design and applications, outputs may be expected to
continue to be subject to change. Also, investigations into the possibility of
subtle or transient effects are still at an early stage. Consequently
diagnostic ultrasound can only be considered safe if used prudently.
Thermal hazard exists with some diagnostic ultrasound equipment, if used
imprudently. A temperature elevation of less than 1·5°C is considered
to present no hazard to human or animal tissue, including a human embryo or
fetus, even if maintained indefinitely. Temperature elevations in excess of
this may cause harm, depending on the time for which they are maintained. A
temperature elevation of 4°C, maintained for 5 minutes or more, is
considered to be potentially hazardous to a fetus or embryo. Some diagnostic
ultrasound equipment, operating in spectral pulsed Doppler mode, can produce
temperature rises in excess of 4°C in bone, with an associated risk of
high temperatures being produced in adjacent soft tissues by conduction. With
some machines colour Doppler imaging modes may also produce high temperature
rises, particularly if a deep focus or a narrow colour box is selected. In
other modes, temperature elevations in excess of 1°C are possible, but are
unlikely to reach 1·5°C with equipment currently in clinical use,
except where significant self-heating of the transducer occurs.
Non-thermal damage has been demonstrated in animal tissues containing gas
pockets, such as lung and intestine, using diagnostic levels of ultrasound
(mechanical index values of 0.3 or more). In view of this, it is recommended
that care should be taken to avoid unnecessary exposure of neonatal lung , and
to maintain MI as low as possible when this is not possible. In other tissues
there is no evidence that diagnostic ultrasound produces non-thermal damage, in
the absence of gas-filled contrast agents. However, in view of the difficulty
of demonstrating small, localised, regions of damage in vivo, the possibility
of this cannot be excluded. The Mechanical Index, if displayed, acts as a guide
to the operator. The use of contrast agents in the form of stabilised gas
bubbles increases the probability of cavitation. Single beam modes (A-mode,
M-mode and spectral pulsed Doppler) have a greater potential for non-thermal
hazard than scanned modes (B-mode, Colour Doppler), although the use of a
narrow write-zoom box increases this potential for scanning modes.
June 2000, reconfirmed by BMUS Council: October
2007 |
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| Statement on
the Use of Diagnostic Ultrasound for Producing Souvenir Images or Recordings in
Pregnancy ECMUS (European Committee of Medical Ultrasound Safety) Statement on
Souvenir Scanning: approved and endorsed by BMUS Council |
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Developments in real-time
three dimensional ultrasonic imaging have led to parents asking for souvenir
(keepsake) video recordings of the fetus, sometimes at several stages during
the pregnancy. An area of concern is the growth of services designed to provide
such images and recordings without any diagnostic element to the scan. Often,
such services are unable to provide counselling or offer guidance if signs of a
fetal abnormality are unexpectedly revealed. Apart from such services, there
many instances of diagnostic scans being prolonged in order to provide such
recordings.
Very little information is currently available regarding possible subtle
biological effects of diagnostic levels of ultrasound on the developing human
embryo or fetus, and the possibility of developmental effects in the brain
cannot be ruled out. There is evidence that diagnostic levels of ultrasound can
influence development of the brain in small animals, although it is not
possible to extrapolate this finding to the human situation. A balance must
always be maintained between diagnostic benefit and risk to the patient.
Therefore, it is difficult to justify souvenir or keepsake scanning that has no
diagnostic benefit.
Recommendations:
- Ultrasound scans should not be performed solely for producing souvenir
images or recordings of a fetus or embryo.
- The production of souvenir images or recordings for the parents to keep is
reasonable if they are produced during a diagnostic scan, provided that this
does not require the ultrasound exposure to be greater in time or magnitude (as
indicated by the displayed MI and TI) than that necessary to produce the
required diagnostic information.
- Attention is drawn to the recommendation of the EFSUMB Clinical Safety
Statement for Diagnostic Ultrasound that ultrasound examinations should be
performed only by competent personnel who are trained and updated in ultrasound
safety matters.
ECMUS October 2006, endorsed by BMUS Council: June
2008 |
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| To find out more about Ultrasound
Safety, please visit our dedicated
Safety Pages. |
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