bk3500 User Guide
(16-01410-EN-04)
Safety Information
47
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.
Fever
A temperature increase of one degree Celsius increase in a patient with fever may
cause complications in certain circumstances; it may be safer to delay the
investigation.
Acoustic Output Measurement
All values are measured in water according to the EN 60601-2-37 and AIUM/NEMA
display standards. For some of the acoustic parameters, an estimated in situ derated
value is given. This is derived assuming a tissue attenuation of 0.3 dB/(cm·MHz)
when the estimated in situ derated value (I) is described by the following equation:
I formula
where the variables are defined in the table below.
It should be stressed that the in situ values given are only applicable when there is
attenuating tissue between the transducer face and the focal point.
Possibility of Adverse Effects
Although it is believed that diagnostic ultrasound causes no significant biological
effects in mammalian tissue, the user should be aware of the hypothetical
possibilities of adverse effects.
Fetal imaging
Current scientific and clinical concern over possible adverse effects is particularly
focused on fetal ultrasound imaging. It is due to the increased sensitivity of
mammalian cells and organs at this phase of their development and the fact that such
a risk could have profound implications on public health. If you use high acoustic
output levels for some reason (see “Functions Affecting Acoustic Output”, below),
be sure to return to B-mode alone and turn down the power level before you do any
fetal imaging.
W
deg
estimated power necessary to raise the temperature of the target tissue one
degree Celsius (W/°C)
Variable Definition
Variable Definition
I
W
Intensity in water at the position where I is maximum
f
transducer frequency (in MHz)
z
distance (in cm) from the transducer face to the position where I is maximum
I
I
w
exp 0,069fz
–
=
