User's Manual

Clarius Ultrasound Scanner - HD3 Scanners Safety Topics
revision 1 51
The TI indicates any conditions that may lead to temperature increase on the surface of the
body, within the body tissue, or at the point of focus of the ultrasound beam on bone. TI
informs you of a potential rise in temperature of body tissue, by estimating temperature
increases in those body tissue with specific properties. The actual temperature increase is
influenced by factors such as tissue type, vascularity, and mode of operation. Use the TI as a
guide for implementing the ALARA principle.
You can choose to display one of the following types of TI indices:
• TIS: Indicates potential for heating within soft homogeneous tissue.
• TIB: Indicates potential for heating at or near the focus after the ultrasound beam has
passed through soft tissue or fluid. For example, at or near second- or third-trimester fetal
bone.
• TIC: Indicates potential for heating of bone at or near the surface. For example, cranial
bone.
MI Display
The higher the MI value, the greater the likelihood of mechanical bioeffects occurring. The
potential for mechanical bioeffects varies by peak rarefactional pressure and ultrasound
frequency. The MI accounts for these two factors. There is no specific MI value that indicates
the occurrence of a mechanical effect. Use the MI as a guide for implementing the ALARA
principle.
When interpreting the MI, remember that it is intended to estimate the potential for
mechanical bioeffects. The higher the index reading, the greater the potential. However,
neither MI = 1 nor any other level indicates that a bioeffect is actually occurring. We should not
be alarmed by the reading, but we should use it to implement the ALARA principle.
Display Accuracy
The MI and TI have a precision of 0.1 unit on the system.
Estimates of the MI and TI display accuracies are shown in the Acoustic Output Tables. The
following factors are considered when estimating the accuracy of the displayed values:
• hardware variations
Variability among scanners and systems is a result of piezoelectric crystal efficiencies,
process-related impedance differences, and sensitive lens-focusing parameter
variations.
• estimation algorithm accuracy
Differences in system pulser voltage control and efficiencies are also contributors to
variability. There are inherent uncertainties in the algorithms used to estimate
acoustic output values over the range of possible system operating conditions and
pulser voltages.