Product Manual

Page 20 of 21
Draft 1.1
MI Mechanical Index. The value of MI at the position of ISPPA.3, (MI@ISPPA.3) may be reported
instead of MI (global maximum value) if ISPPA.3 is ≤ 190W/cm2 .
p
r.3
derated peak rarefactional pressure (megapascals) associated with the transmit pattern giving
rise to the value reported under MI.
W
o
ultrasonic power (milliwatts). For the operating condition giving rise to ISPTA.3, Wo is the total
time-average power; for the operating condition subject to reporting under ISPPA.3, Wo is the
ultrasonic power associated with the transmit pattern giving rise to the value reported under ISPPA.3.
f
c
center frequency (MHz). For MI and ISPPA.3, fc is the center frequency associated with the transmit
pattern giving rise to the global maximum value of the respective parameter. For ISPTA.3, for
combined modes involving beam types of unequal center frequency, fc is defined as the overall range
of center frequencies of the respective transmit patterns.
z
sp
the axial distance at which the reported parameter is measured (centimeters).
x
-6
, y
-6
are respectively the in-plane (azimuthal) and out-of-plane (elevational) -6 dB dimensions in the x-y
plane where zsp is found (centimeters).
PD pulse duration (microseconds) associated with the transmit pattern giving rise to the reported value
of the respective parameter.
PRF the pulse repetition frequency (Hz) associated with the transmit pattern giving rise to the reported
value of the respective parameter.
EBD the entrance beam dimensions for the azimuthal and elevational planes (centimeters).
EDS the entrance dimensions of the scan for the azimuthal and elevational planes (centimeters).
The reporting values for ultrasonic power, W0, and non-derated spatial average temporal average ISATA
required by paragraph 2.1.2 of the FDA Guidance [3] as well as the derated spatial-peak temporal-average
intensity, ISPTA.3, provided for reference only, are calculated for all probes as illustrated in the sample
calculations below.
For Non-Auto scanning modes reporting parameters are calculated as:
W
0
= I
SPTA.0
* PF
I
SATA.0
= W
0
/(entrance beam area)
I
SPTA.3
= I
SPTA.0
* e
-0.069 fc z
Where I
SPTA.0
, is the non-derated spatial-peak temporal-average intensity, ISATA.0 is the nonderated spatial-
average temporal-average intensity at the transducer face and I
SPTA.3,
is the derated spatial-peak temporal-
average intensity, fC, the waveform center frequency, z, the axial distance between the probe and
hydrophone, PF, the power factor which is calculated by integrating the normalized cross axis and raster scan
data selecting the largest PF value, which is an “effective area” used to calculate W
0
, the ultrasonic power.