M y L a b
–
S A F E T Y A N D S T A N D A R D
2-15
Symbols Used in Indices Equations
Symbol
Definition
A
aprt
(cm
2
)
Active aperture area
d
eq
(z) (cm)
Equivalent beam diameter
)
(
)
(
4
3
.
3
.
z
I
z
W
TA
D
eq
(cm)
Equivalent aperture diameter
aprt
A
4
f
c
(MHz)
Center frequency.
I
SPTAB.3
(mW/cm
2
)
Equivalent to the spatial peak temporal average derated
(0.6 dBcm
-1
MHz
-1
) intensity
I
TA.3
(z) (mW/cm
2
)
Temporal average intensity derated to depth z
W
0
(mW)
Time average acoustic power at source
W
01
(mW)
Time average acoustic power at the source emitted from
the central centimeter of the active aperture
W.3 (z) (mW)
Time average acoustic power derated to depth z
X
W
(mW/cm)
Acoustic power per unit linear length (for example of a
linear array)
z (cm)
Depth from the surface along the beam axis
z
bp
(cm)
Break point depth (minimum depth for intensity
measurements in the TIS(unscanned) models)
zbp = 1.5Deq
z
B.3
(cm)
Depth of the maximum temperature rise in the bone at
focus model
p
r.3
(zsp)
Peak rarefactional pressure (in MPa) derated by 0.3
dBcm
-1
MHz
-1
to the point on the beam axis zsp where
pulse intensity integral (PII.3) is maximum
