28 Chapter 1
Monitor Display
The Mechanical Index (MI) and Thermal Index (TI) can be viewed in all scanning
modes.
Thermal and Mechanical Indices
The MI and TI indices are intended to allow users to implement the ALARA [10, 11]
(As Low As Reasonably Achievable) principle using an indicator related to a
potential bioeffect.
The full details of the indices are given in references [3] and [9], but the formulas are
given below.
MI Formula
where the variables are defined in the table below.
TI Formula
where the variables are defined in the table below.
Blood
perfusion and
TI
As a rule of thumb, the Thermal Index (TI) indicates the highest expected
temperature increase in degrees Celsius. It is based on an average level of blood
perfusion. The displayed TI may underestimate the temperature rise in poorly
perfused tissues; you must take this into account when deciding on the maximum TI
you will allow. Conversely, in areas with a rich perfusion of blood the temperature
increase will be less than the displayed TI indicates.
Variable
Definition
P
r0.3
(z
sp
)
Peak Rarefactional Pressure (MPa), derated by 0.3dB/cm·MHz,
measured at z
sp
, the point on the beam axis where pulse intensity integral
(PII
0.3
) is maximum
f
c
measured center frequency (in MHz)
Variable
Definition
W
0
time-averaged acoustic power of the source or other power parameter (W)
W
deg
estimated power necessary to raise the temperature of the target tissue one
degree Celsius (W/°C)
M
I
P
r0.3
z
sp
(
)
f
c
------------------------
=
TI
W
0
W
deg
-------------
=
Содержание Pro Focus 2202
Страница 1: ...English BB1279 A June 2005 Pro Focus 2202 Extended User Guide ...
Страница 14: ...14 ...
Страница 15: ...Part 1 Basics ...
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Страница 32: ...32 Chapter 1 ...
Страница 48: ...48 Chapter 2 ...
Страница 49: ...Part 2 Working with the Image ...
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Страница 98: ...98 Chapter 5 ...
Страница 117: ...Part 3 Imaging Modes ...
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Страница 136: ...136 Chapter 8 ...
Страница 152: ...152 Chapter 10 ...
Страница 164: ...164 Chapter 12 ...
Страница 165: ...Part 4 Setting up and Maintaining Your System ...
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Страница 200: ...200 Chapter 13 ...
Страница 208: ...208 Chapter 14 ...
Страница 209: ...Part 5 Pro Packages ...
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Страница 288: ...288 Chapter 19 ...
Страница 313: ...Part 6 Appendixes ...
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Страница 344: ...344 Appendix C ...