Clarius Scanner HD3 Safety Topics
revision 9 55
Acoustic output defaults are set when you select an application. Factory defaults vary
with scanner, application, and mode. Defaults have been chosen below the FDA limits
for intended use.
• Imaging Mode Controls:
When a new imaging mode is selected, both the TI and MI may change to default
settings. Each mode has a corresponding pulse repetition frequency and maximum
intensity point. In combined or simultaneous modes, the TI is the sum of the
contribution from the modes enabled, and the displayed MI is the largest of the MI
values associated with each mode and focal zone enabled. The system will return to
the previously selected state if a mode is turned off and then reselected.
• Scanner:
Each scanner type has unique specifications for contact area, beam shape, and center
frequency. Selecting a scanner initializes its default settings, which varies by scanner,
application, and selected mode. These defaults are set below the FDA limits for
intended use.
Example of reducing output:
Imagine we are getting ready to do a liver scan. The first thing we need to do is select the
appropriate scanner frequency. Next, we adjust the output intensity (or power) transmit
setting. We check to make sure that it is positioned at the lowest possible setting to produce
an image. We adjust the focus to the area of interest and then increase the receiver gain to
produce a uniform representation of the tissue. If we can obtain a good image by increasing
the gain, we can lower the output and continue to increase the gain. Only after making these
adjustments and if tissue penetration or echo amplitude levels are inadequate should we
increase the output to the next higher level.
Acoustics
The scanner is the most important factor in image quality. Optimal imaging cannot be obtained
without the correct scanner. The system is optimized for use based on your scanner selection.
The system limits patient contact temperature to 43°C (109°F), and acoustic output values to
their respective U.S. Food and Drug Administration limits. A power-protection circuit protects
against over-current conditions. If the power monitor protection circuit senses an over-current
condition, then the drive voltage to the scanner is shut off immediately, preventing
overheating of the scanner surface and limiting acoustic output. Validation of the power
protection circuit is done under normal system operation.
A temperature elevation of less than 1.5°C (2.7°F) is considered harmless to human tissue
(including embryo or fetus). Temperatures in excess of this may cause harm, depending on the
length of time maintained. A temperature elevation of 4°C (7.2°F), maintained for five minutes
or more, is considered to be potentially hazardous to a fetus or embryo.
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