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Instructions For Use
EN
TI (Thermal Index)
Heating of tissues is caused by absorption of ultrasound when the ultrasound energy
is applied.nThe temperature rise is determined by the acoustic intensity, exposed area
and thermophysicalbproperties of the tissue.
In order to indicate the potential for temperature rise caused by thermal effects, the
AIUM andNEMA 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
(1.8ºF).
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..
Measurement Uncertainty
The uncertainties in the measurements were predominantly systematic in origin;
the random uncertainties were negligible in comparison. The overall systematic
uncertainties were determined as follows:
1. Hydrophone Sensitivity
Based on the HNP-0400 hydrophone calibration certificate, the hydrophone
measurement uncertainty for 1-15MHz is 1 dB, which is equivalent to an uncertainty
of ±12.20% for intensity and ±6.10% for pressure. This uncertainty is used in PW
measurement uncertainty assessment.
2. Digitizer
Based on the oscilloscope calibration certificate, the oscilloscope uncertainty is ±1.16%
forintensity and ±0.58% for pressure.
3. Temperature
Based on the temperature variation of the water bath, the uncertainty is ±1.6% for
intensity and ±0.8% for pressure.
4. Spatial Averaging
±10.2% for intensity, and ±6.1% for pressure.
5. Non-linear Distortion:
N/A. No effects of nonlinear propagation were observed.
Since all the above error sources are independent, they may be added on an RMS
basis, giving a total uncertainty of ± 26.62 percent for all intensity values reported, ±
13.31 percent for all the pressure values and ± 14.52 percent for the Mechanical Index.
