B-K Medical Pro Focus 2202, User Manual

Page: 29 / 356

General and Safety Information 29
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 and AIUM/NEMA display
standards [3, 8, 9]. For the 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 [3, 9], the user should be aware of the hypothetical
possibilities of adverse effects [10, 12, 13].
Fetal
scanning
Current scientific and clinical concern over possible adverse effects is particularly
focused on fetal ultrasound scanning. 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 scanning.
Functions Affecting Acoustic Output
The scanner has a control function that ensures that neither the I
SPTA
nor MI nor TI
value exceeds the maximum allowable value. When necessary, the scanner will
reduce the output voltage and/or PRF (pulse repetition frequency) to the transducer
in order to comply with requirements.
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 –
( )
=