Product Manual

Important safety considerations
Vscan – User Manual 7-17
GM092207 02
Display Accuracy and Acoustic Measurement Uncertainties
The display accuracy and measurement precision of the output
display are summarized in the table below. Accuracy of the
output display (TI, MI) parameters depends on the
measurement system precision, the acoustic model used to
calculate the parameters and variation in the acoustic output of
probes and systems. The measurement precision and overall
accuracy of the measurements have been assessed by
determining both the random and the systematic uncertainties
and given in percent at 95% confidence level.
a. Accuracy = (Measured value - displayed value)/displayed
value * 100%
System controls affecting acoustic output
The operator controls that directly affect the acoustic output are
discussed in the Acoustic Output Data Tables (see page 8-1).
These tables show the highest possible acoustic intensity for a
given mode, obtainable only when the maximum combination of
control settings is selected. Most settings result in a much lower
output. It is important to note the following:
• The duration of an ultrasound examination is as important
as the acoustic output, since patient exposure to output is
directly related to the exposure time.
• Better image quality yields faster clinical results, making it
possible to complete the relevant ultrasound examination
more rapidly. Therefore, any control that improves the
quality of the examination can help to reduce patient
exposure, even though it may not directly affect acoustic
output.
Application selection
Selecting the application appropriate to a particular ultrasound
examination automatically provides acoustic output limits within
FDA guidelines for that application. Other parameters which
optimize performance for the selected application are also set
Parameter Estimated accuracy
a
Measurement precision
black and white/color
Pressure, MI ±25% ±15%
Power, TI ±50% ±40%