No. 2B771-004EN*M
24-9
24.2 Using MI/TI (in the USA and Canada)
24.2.1 Basic knowledge of MI/TI
(1) Concerns with bioeffects
Diagnostic ultrasound is recognized as being safe. In fact, there have been no
reports of injuries to patients caused by diagnostic ultrasound.
It cannot be stated categorically that ultrasound is 100% safe. Studies have
revealed that ultrasound with extremely high intensity is harmful to body tissues.
This rapid advance has generated concerns about the potential risk of bioeffects
when new applications or diagnostic technologies become available.
(2) Mechanical effects and thermal effects
Studies have revealed that two different kinds of ultrasound characteristics affect
human bodies: one is the mechanical effects due to cavitation generated when
the negative pressure of ultrasound exceeds a certain limit, and the other is the
effects due to thermal energy generated when tissues absorb ultrasound. The
levels of these two kinds of effects are represented by indices: the MI (Mechanical
Index) and the TI (Thermal Index), respectively.
(3) MI/TI
values
The smaller the MI/TI values, the less the bioeffects.
(4) Controlling the ultrasound output
In 1976, the FDA in the USA established limits to the acoustic output level for
diagnostic ultrasound equipment (TRACK1), along with the rapid advance in
diagnostic ultrasound technology, and the versatile proliferation of its applications,
in order to ensure the safety of patients. Thereinafter, manufacturers were
required to control the acoustic output level below the limits, when releasing new
diagnostic ultrasound systems on the market.
NOTE:
Ispta.3 may be represented as
I
zpta,
(
= 0.3 dB/cm/MHz)
(IEC 60601-2-37).
Maximum acoustic power specified by FDA (TRACK1)
Application
Ispta.3
(mW/cm
2
)
Isppa.3
(W/cm
2
)
MI
Peripheral blood vessels
720
190
1.9
Cardiovascular systems
430
190
1.9
Fetal and other
94
190
1.9
Eyes 17
28
0.23
Summary of Contents for Aplio 500 TUS-A500
Page 41: ...No 2B771 004EN M 6 2 Systems with the main power switch on the side ...
Page 63: ...No 2B771 004EN M 9 3 Systems with the main power switch on the side ...
Page 92: ...No 2B771 004EN M 13 4 PIMS page 2 2 Refer to section 19 Storing Image Data ...
Page 163: ...No 2B771 004EN M 18 5 18 2 Needle Mark Display and Angle Change Procedures ...
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