SONOTRAX(2009) Series Ultrasonic Pocket Doppler User Manual
92
In order to indicate the potential for temperature rise
caused by thermal effects, the AIUM and NEMA
formulate thermal index (TI). It is defined as the ratio
of the total acoustic power to the acoustic power
required to raise the tissue temperature by 1ºC
(1.8°F).
According to different thermophysical properties of
the tissue, TI is divided into three kinds: TIS, TIB
and TIC.
TIS (Soft Tissue Thermal Index): It provides an
estimate of potential temperature rise in soft or
similar tissues.
TIB (Bone Thermal Index): It provides an estimate of
potential temperature rise when the ultrasound beam
passes through soft tissue and a focal region is in the
immediate vicinity of bone.
TIC (Cranial Bone Thermal Index): It provides an
estimate of potential temperature rise in the cranial
bones or superficial bones.
A4.3.3 Measurement Uncertainties
The uncertainties in the measurements were
predominantly systematic in origin; the random
uncertainties were negligible in comparison. The
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