User's Manual

Rev.1.01
2022. 03.
44 / 96
Doc # : BN-SM-EOP-01
6.2 Acoustic Power Principle
Warnings:
- Guidance for the use of diagnostic ultrasound is defined by the “As Low As
Reasonably Achievable (ALARA)” principle. By keeping ultrasound exposure as low
as possible while obtaining diagnostic images, users can minimize ultrasonic
bioeffects.
- The operator should notice the effect of the heat on the patient body when the exam is
performed around the bones and the nearby soft tissues which can transform the ultrasound
energy to heat energy. Take special care to the fetal whose bones are growing.
6.2.1 Biological Safety
Ultrasound waves may have damaging effects on cells and, therefore, may be harmful to the
patient. If there is no medical benefit, minimize the exposure time and maintain the ultrasound
wave output level at a low setting. Please refer to the ALARA principle.
6.2.2 Thermal Index (TI) & Mechanical Index (MI)
The system output display comprises two basic indices: a thermal index (TI) and a
mechanical index (MI). These shows on the Right-Top side on the app.
- Meaning of MI & TI
Mechanical bioeffects are threshold phenomena that occur when a certain level of
output is exceeded. The threshold level varies, however, with the type of tissue. The
MI accounts for these two factors. The higher the MI value, the greater the likelihood
of mechanical bioeffects occurring. However, there is no specific MI value that means
that a mechanical effect will occur. The MI should be used as a guide for
implementing the ALARA principle.
The TI informs the user of the potential for temperature increase occurring at the
body surface, within body tissue, or at the point of focus of the ultrasound beam on
bone. The TI is an estimate of the temperature increase in specific body tissues. The
actual amount of any temperature rise is influenced by factors such as tissue type,
vascularity, and mode of operation. The TI should be used as a guide for
implementing the ALARA principle. Depending on the examination and type of tissue