Operator Awareness And Actions To Minimize Bioeffect - GE LOGIQ 500 Advanced Reference Manual

Operator Awareness and Actions to Minimize Bioeffect

Tissue characteristics
LOGIQ 500 Advanced Reference Manual
2276614–100 Rev. 0
The operator must be aware of the particular conditions that
exist during the examination to recognize the potential for
bioeffect and then take appropriate action to reduce the risk.
The recognition of potential harm comes from an understanding
of tissue characteristics and a real-time knowledge of acoustic
output. Taking appropriate action requires familiarity with
equipment operation and examination skills like implementing
alternative techniques for obtaining the same diagnostic
information.
Tissue characteristics vary considerably throughout the body.
They influence the acoustic field and determine the
heating/cooling rates and cavitation potential. Ultrasound
energy dissipates as it passes through the tissue causing the
deeper tissue to encounter much lower levels. Some tissues
like bone readily convert ultrasound energy to heat, while others
like blood and amniotic fluid pass the energy on to adjacent
tissue relatively unattenuated.
A particular situation that represents a tissue combination
requiring extra precaution is a third trimester transabdominal
fetal examination where there is a very thin abdominal wall and
a long fluid path. The relative lack of attenuating tissue along
the acoustic path will significantly increase the available energy
in the fetal tissue. Additionally, fetal tissues are more
susceptible to long term injury due to nature of developing
tissue. Focusing the ultrasound beam on or near fetal bone
further increases the risk.
Other than fetal tissue, there is increased susceptibility for
heating in any tissue that cannot easily conduct or distribute
heat due to low blood perfusion. As the examination
progresses, the operator must be aware of changing tissue
conditions.
Bioeffects
6–5