Acoustic Output
Vscan Air – User Manual 8-5
Direction GP092020-1EN Rev 18
Controls Affecting Acoustic Output
The initial means by which the user can affect acoustic output
are by 1) selecting a probe, 2) selecting an application (exam
category) and then 3) selecting the imaging mode or imaging
characteristics (depth, color ROI center position). This is
achieved through an acoustic output control scheme in which all
parameters that directly or indirectly affect acoustic output are
fed to the control algorithm. The algorithm estimates all relevant
parameters and compares them to the FDA limits.
Output levels remain below the limits with a 95% confidence
margin. The absolute maximum allowable output for all
applications is:
• ISPTA less than or equal to 720 mW/cm2
• MI less than or equal to 1.9
• TI less than or equal to 6
The Acoustic Output Control Scheme
Input Parameters Control Algorithm Output Parameters
Transmit frequency ---->
Transmit apodization ---->
Focal depth ---->
Steering angle ----> Output control never to
exceed limit minus
tolerances
Sector size ----> ----> Transmit voltage control to
Beamformer
Pulse repetition frequency ---->
Pulse length ---->
Mode combination ----> I
SPTA
----> Thermal/mechanical
Indices to Output Display
Application ----> TIS/TIB/TIC
Acoustic ouput control ----> MI
Probe sensitivity ---->
FDA Limits @ 95%
confidence tolerance
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