Siemens Acuson S3000 - Definitions

Appendix F Acoustic Output Reference
F - 8 Instructions for Use
Definitions
Symbol
Definition
Units
FDA IEC FDA IEC
MI MI Mechanical Index Same as FDA n/a
TIS
scan
TIS Scan Soft Tissue Thermal Index in autoscanning mode Same as FDA n/a
TIS
non-scan
TIS Non-scan Soft Tissue Thermal Index in non-autoscanning mode Same as FDA n/a
TIB TIB Bone Thermal Index Same as FDA n/a
TIC
TIC
Cranial Thermal Index
Same as FDA
n/a
A
aprt
A
aprt
Area of the active aperture -12dB output beam area cm
2
P
r.3
p
ra
Derated peak rarefactional pressure Attenuated peak-rarefactional
acoustic pressure
MPa
W
o
P Ultrasonic power, except for TIS
scan
in which case it is the
ultrasonic power passing through a one centimeter
window
Output power mW
W
.3
(z
1
) P
α
(z
s
) Derated ultrasonic power at axial distance z
1
Attenuated output power at z
s
mW
I
TA.3
(z
1
) I
ta, α
(z
s
) Derated spatial-peak, temporal-average intensity at axial
distance z
1
Attenuated temporal-average
intensity at z
s
mW/cm
2
z
1
z
s
Axial distance corresponding to the location of the
max [min (W
.3
(z), I
TA.3
(z) x 1 cm
2
)], where z > z
bp
Depth for TIS
cm
2
z
bp
z
bp
1.69 (A
aprt
)
1/2
Break-point depth
cm
z
sp
z
b
Axial distance at which TIB is a maximum (i.e., z
sp
= z
B.3
) Depth for TIB cm
z@PII
.3max
z at max. I
pi,α
The axial distance corresponding to the maximum of the
derated spatial-peak pulse intensity integral
(megapascals).
Depth at the point where the
free-field, attenuated pulse intensity
integral is a maximum
cm
d
eq
(z) d
eq
(z) Equivalent beam diameter as a function of axial distance
z, and is equal to
0.5
TA
o
(z)
I
W
4






















π
where I
TA
(z) is
the temporal-average intensity as a function of z
Equivalent beam diameter at axial
distance z
cm
f
c
f
awf
Center frequency Acoustic working frequency MHz
Dim. of A
aprt
Dim. of A
aprt
Active aperture dimensions for the azimuth and
elevational planes
Same as FDA cm
PD t
d
Pulse duration Same as FDA μs
PRF prr Pulse repetition frequency Pulse repetition rate Hz
p
r
@PII
max
p
r
at max. I
pi
Peak rarefactional pressure at the point where the free-
field, spatial-peak pulse intensity integral is a maximum
Same as FDA MPa
d
eq
@PII
max
d
eq
at max. I
pi
Equivalent beam diameter at the point where the
free-field, spatial-peak pulse intensity integral is a
maximum
Same as FDA cm
FL FL Focal Length, or azimuthal and elevational lengths, if
different
Same as FDA cm
I
PA.3
@MI
max
I
pa,α
at max. MI Derated pulse-average intensity at the point of global
maximum reported MI
Same as FDA W/cm
2
Note: Pulse-average intensity (I
pa
) is the ratio of the pulse-intensity integral (I
pi
) to the pulse
duration (t
d
).