SonoSite S-Cath - Terms Used in the Acoustic Output Tables

Chapter 6: Safety 119
Safety
Terms used in the acoustic output tables
Table 37: Acoustic Output Terms and Definitions
Term Defin ition
I
SPTA.3
Derated spatial peak, temporal average intensity in units of milliwatts/cm
2
.
TI type Applicable thermal index for the transducer, imaging mode, and exam type.
TI value Thermal index value for the transducer, imaging mode, and exam type.
MI Mechanical index.
I
pa.3
@MImax
Derated pulse average intensity at the maximum MI in units of W/cm
2
.
TIS (Soft tissue thermal index) is a thermal index related to soft tissues. TIS scan is
the soft tissue thermal index in an auto-scanning mode. TIS non-scan is the
soft tissue thermal index in the non-autoscanning mode.
TIB (Bone thermal index) is a thermal index for applications in which the
ultrasound beam passes through soft tissue and a focal region is in the
immediate vicinity of bone. TIB non-scan is the bone thermal index in the
non-autoscanning mode.
TIC (Cranial bone thermal index) is the thermal index for applications in which
the ultrasound beam passes through bone near the beam entrance into the
body.
A
aprt
Area of the active aperture measured in cm
2
.
P
r.3
Derated peak rarefactional pressure associated with the transmit pattern
giving rise to the value reported under MI (Megapascals).
Wo Ultrasonic power, except for TIS
scan
, in which case it is the ultrasonic power
passing through a one centimeter window in units of milliwatts.
W
.3
(z
1
) Derated ultrasonic power at axial distance z
1
in units of milliwatts.
I
SPTA.3
(z
1
) Derated spatial-peak temporal-average intensity at axial distance z
1
(milliwatts per square centimeter).
z
1
Axial distance corresponding to the location of maximum [min(W
.3
(z), I
TA.3
(z)
x 1 cm
2
)], where z > zbp in centimeters.
z
bp
1.69 in centimeters.
z
sp
For MI, the axial distance at which p
r.3
is measured. For TIB, the axial distance
at which TIB is a global maximum (for example, z
sp
= z
b.3
) in centimeters.
Aaprt()