2 – 22 HS40 Service Manual
2.5. Biological Safety
For safety instructions concerning probes and biopsies, refer to ‘Chapter 9. Probes’.
WARNING
Ultrasound waves may have damaging effects on cells and, therefore, may
be harmful to the patient. If there is no medical benefit, minimize the exposure
time and maintain the ultrasound wave output level at low. Please refer to the
ALARA principle.
Do not use the system if an error message appears on the video display
indicating that a hazardous condition exists. Note the error code, turn off the
power to the system, and call Samsung Medison customer service
department.
Do not use a system that exhibits erratic or inconsistent functioning.
Discontinuities in the scanning sequence are indicative of a hardware failure
that should be corrected before use.
The system limits the maximum contact temperature to 43 degrees Celsius,
and the ultrasonic wave output observes American FDA regulations.
2.5.1. ALARA Principle
Guidance for the use of diagnostic ultrasound is defined by the “As Low As Reasonably
Achievable” (ALARA) principle. The decision as to what is reasonable has been left to the
judgment and insight of qualified personnel. No set of rules can be formulated that would be
sufficiently complete to dictate the correct response to every circumstance. By keeping
ultrasound exposure as low as possible, while obtaining diagnostic images, users can minimize
ultrasonic bioeffects.
Since the threshold for diagnostic ultrasound bioeffects is undetermined, it is the sonographer’s
responsibility to control the total energy transmitted into the patient. The sonographer must
reconcile exposure time with diagnostic image quality. To ensure diagnostic image quality and
limit exposure time, the Ultrasound System provides controls that can be manipulated during the
exam to optimize the results.
The ability of the user to abide by the ALARA principle is important. Advances in diagnostic
ultrasound, not only in the technology but also in its applications, have resulted in the need for
increased and improved information to guide the user. The output indices are designed to
provide that important information.
There are a number of variables, which affect the way in which the output display indices can be
used to implement the ALARA principle. These variables include mass, body size, location of
the bone relative to the focal point, attenuation in the body, and ultrasound exposure time.
Exposure time is an especially useful variable, because the user controls it. The ability to limit
the index values over time supports the ALARA principle.
2.5.1.1. Applying ALARA
The system imaging mode used depends upon the information needed. 2D mode and M mode
imaging provide anatomical information, while Doppler, Power, and Color imaging provide
information about blood flow. Scanned modes, like 2D mode, Power, or Color, disperse or
scatter the ultrasonic energy over an area, while an unscanned mode, like M mode or Doppler,
concentrate the ultrasonic energy. Understanding the nature of the imaging mode being used
allows the sonographer to apply the ALARA principle with informed judgment. The probe
frequency, system set-up values, scanning techniques, and operator experience aid the
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