Safety
2-18 Vscan Air – User Manual
Direction GP092020-1EN
Rev 18
Ispta
The Ispta is the Spatial Peak Temporal Average Intensity. The
absolute maximum limit of Ispta is 720 mW/cm
2
as set by the
FDA guidance of June 27, 2019 for diagnostic ultrasound
systems and transducers.
Acoustic output and display on Vscan Air
MI and TI values are displayed on the scanning screen.
The display resolution of MI and TI is 0.1.
The maximum possible MI and Ispta on the Vscan Air CL is
within the limits set in Track 3 in the FDA guidance of June 27,
2019 for diagnostic ultrasound systems and transducers, MI
<1.9 and Ispta <720 mW/cm
2
. The Vscan Air provides the ability
to select the display of any of the TI categories independent of
the category set as the factory default setting. The TI category
display changes when 'tapping' the TI value displayed in the
lower left corner of the screen while scanning, refer ‘Black/white
imaging mode (B-mode)’ on page 3-15.
Accuracy of the displayed acoustic output and acoustic measurement
uncertainties
The accuracy of the displayed acoustic output and the acoustic
measurements uncertainty is summarized in the table below.
Accuracy of the output display (TI, MI) parameters depends on
the measurement system uncertainty, the acoustic model used
to calculate the parameters and variation in the acoustic output
of probes and systems. The overall measurement uncertainty
has been assessed by determining Type A and Type B
uncertainties following the ISO Guide to the Expression of
Uncertainty in Measurement (GUM) at a 95% confidence level
for MI and TI from and above the 0.4 limit given by IEC/
EN60601-2-37 Ed2, Amd1.
Accuracy of the displayed acoustic output = (Measured value
-Acoustic output display value)/Acoustic output display value *
100%
Table 2-4: Accuracy of the displayed acoustic output
Parameter
Displayed acoustic output
accuracy
Measurement uncertainty
Black/ white (B-mode) and Color flow
(Color doppler)
Pressure, MI ±25% ±15%
Power, TI ±50% ±30%
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