Q9 Digital Color Doppler Ultrasound System
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MI = Pr’ / sqrt(fc)
Pr’ is the de-rated (0.3) peak rare-fractional pressure in Mpa at the point where PII is the maximum,
and fc is the center frequency in MHz. PII is the Pulse Intensity Integral that the total energy per unit
area carried by the wave during the time duration of the pulse. The peak rare- fractional
pressure is measured in hydrophone maximum negative voltage normalized by the hydrophone calibration
parameter.
Display Guideline:
For different operation modes, different indices must be displayed. However, only one index needs to be shown at a
time. Display is not required if maximum MI is less than 1.0 for any setting of the operating mode, or if maximum
TI is less than 1.0 for any setting of the operating mode. For TI, if the TIS and TIB are both greater than 1.0, the
scanners need not be capable of displaying both indices simultaneously. If the index falls below 0.4, no display is
needed. The display increments are no greater than 0.2 for index value less than one and no greater than 1.0 for index
values greater than one (e.g. 0.4, 0.6, 0.8, 1, 2, 3).
Display and Report in Different Mode
Located on the upper middle section of the system display monitor, the acoustic output display provides the operator
with real-time indication of acoustic levels being generated by the system.
For B-Scan Mode
Only display and report MI, and start from 0.4 if maximum MI > 1.0, display in increments of 0.2.
For Color Mode
Only display and report TIS or TIB and start from 0.4 if maximum TI > 1.0, display in increments of 0.2 for
values of indices of 2.0 or less, and 0.5 for values of indices greater than 2.0.
For Doppler Mode
Only display and report TIS or TIB and start from 0.4 if maximum TI > 1.0, display in increments of 0.2 for
values of indices of 2.0 or less, and 0.5 for values of indices greater than 2.0.
Below is a simple guideline for the user when TI exceeds one limit exposure time to 4
(6-TI)
minutes based on the
‘National Council on Radiation Protection. Exposure Criteria for Medical Diagnostic Ultrasound: I. Criteria Based
on Thermal Mechanisms. Report No.113 1992’.
Operator Control Features:
The user should be aware that certain operator controls may affect the acoustic output. It is recommended to use
the default (or lowest) output power setting and compensate using Gain control to acquire an image.
Other than the output power setting in the soft-menu, which has the most direct impact on the power; the PRF,
image sector size, frame rate, depth, and focal position also slightly affect the output power. The default setting is
normally around 70% of the allowable power depending on the exam application mode.
Controls Affecting Acoustic Output
The potential for producing mechanical bioeffects (MI) or thermal bioeffects (TI) can be influenced by certain