User's Manual

Clarius Ultrasound Scanner - HD3 Scanners Safety Topics
revision 1 48
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.
The system does not exceed a spatial peak temporal average intensity (I
SPTA
) of 720 mW/cm
2
for all imaging modes. The system follows the Output Display Standard (IEC 60601-2-37) and
falls within the Track 3 acoustic output limits.
Indirect Controls
Controls affecting imaging mode, freeze, and depth indirectly affect output. The imaging mode
determines the nature of the ultrasound beam. Because freeze stops all ultrasound output but
keeps the last image displayed on screen, you can use it to limit exposure time while studying
an image and maintaining scanner position during a scan. Some controls, such as depth, show
a rough correspondence with output, and may be used as a general means for indirectly
reducing MI or TI.