KOSMOS User Guide 91
Biological safety
Understanding the nature of the imaging mode being used allows users to apply
the ALARA principle with informed judgment. Additionally, the Kosmos Torso
frequency, Kosmos Bridge setup values, scanning techniques, and experience
allow users to meet the definition of the ALARA principle.
The decision as to the amount of acoustic output is, in the final analysis, up to the
user. This decision must be based on the following factors: type of patient, type
of exam, patient history, ease or difficulty of obtaining diagnostically useful
information, and the potential localized heating of the patient due to transducer
surface temperatures. Prudent use of KOSMOS occurs when patient exposure is
limited to the lowest index reading for the shortest amount of time necessary to
achieve acceptable diagnostic results.
Although a high index reading does not mean that a bioeffect is actually
occurring, a high index reading should be taken seriously. Every effort should be
made to reduce the possible effects of a high index reading. Limiting exposure
time is an effective way to accomplish this goal.
There are several system controls that the operator can use to adjust the image
quality and limit the acoustic intensity. These controls are related to the
techniques that a user might use to implement ALARA.
Output display and display accuracy
OUTPUT DISPLAY
KOSMOS displays the two bioeffect indices prescribed by IEC 60601-2-37.
Medical electrical equipment. Part 2-37: Particular requirements for the safety of
ultrasonic medical diagnostic and monitoring equipment.
The thermal index (TI), provides a measure of the expected temperature
increase.
Thermal index
TI is an estimate of the temperature increase of soft tissue or bone. There are
three TI categories: TIS, TIB, and TIC. However, since KOSMOS is not
intended for transcranial applications, the TI for cranial bone at the surface
(TIC) is not available for display on the system. The following TI categories
are available for display:
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