Clarius Scanner HD3 Safety Topics
revision 9 50
undetermined, and the definition of “reasonable” is left to the judgment and insight of
qualified personnel. No set of rules can be formulated that would be sufficiently complete to
dictate the correct response to every circumstance. By keeping ultrasound exposure as low as
reasonably achievable as you obtain diagnostic images, you can minimize ultrasonic bioeffects.
Output display indices are designed to provide more quality information, to help guide the
sonographers using ultrasound technology, in applying the ALARA principle. Some variables
that affect the way output display indices can be used to implement the ALARA principle:
• index values
• body size
• location of the bone relative to the focal point
• attenuation in the body
• ultrasound exposure time (an especially useful variable, as it is controlled by you)
Applying ALARA
The system's imaging mode you select depends on the information needed. Understanding the
nature of the imaging mode used, the scanner frequency, system setup values, scanning
techniques, exposure time, system and scanner capabilities, and operator experience allows
the sonographer to apply the ALARA principle with informed judgment and meet the definition
of the ALARA principle.
The amount of acoustic output is up to the system operator. 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 scanner surface temperatures. The objective is to limit patient exposure to the lowest
index reading for the shortest amount of time achieving acceptable diagnostic results.
A high index reading does not necessarily indicate the occurrence of a bioeffect; however, it
must be taken seriously. It is your responsibility to make every effort to reduce the possible
effects of a high index reading by limiting exposure time.
System controls (direct, indirect, and receiver) can be used to adjust the image quality and
limit the acoustic intensity and are related to the techniques that an operator could use to
implement ALARA.
Using System Controls to Implement ALARA
Direct Controls
The system has no direct control for output; therefore, the sonographer must control exposure
time and scanning technique to implement the ALARA principle. To ensure that acoustic and
thermal limits are not exceeded for all imaging modes, the Clarius Ultrasound Scanner is
designed to automatically adjust output.
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