bk ultrasound Flex Focus 1202, User Manual

Page: 39 / 66

Flex Focus 1202 User Guide (BB1756-Q) Safety Information 39
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, 10], the user should be aware of the hypothetical
possibilities of adverse effects [11, 13, 14].
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.
Functions Affecting Acoustic Output
The system has a control function that ensures that neither the I
SPTA
nor MI nor TI
value exceeds the maximum allowable value. When necessary, the system will
reduce the output voltage and/or PRF (pulse repetition frequency) to the transducer
to comply with requirements.
Some of the system functions can affect the acoustic output, as listed here.
(Instructions for using these functions are given in the relevant sections of this user
guide.)
•
Sizing functions such as ROI (region of interest) – in general, smaller size
results in higher acoustic intensity because the pulse repetition frequency (PRF)
is higher or the ultrasound beam is more strongly focused.
•
Focus – in general, strongly focusing the beam makes the acoustic intensity
higher.
•
Frame rate – higher frame rate results in higher acoustic intensity.
•
Range – increasing the Doppler range increases the acoustic intensity by
increasing the PRF.
•
CFM Resolution – higher resolution increases the acoustic output.
•
Color box size – narrowing the color box generally increases the acoustic output
within it.
The user can set a Thermal Index limit. This will provide an upper limit for acoustic
output.
Default Acoustic Output
After the system has been turned off, the transducers will start in the default setup
when the system is turned on again. The default setup may be factory-defined or
defined by the user.
The factory-defined default setup values of acoustic output for each transducer are
listed in the Technical Data (BZ2100).