Philips HD11 XE - Page 29

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HD11 XE Getting Started
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Safety
response to every circumstance. By keeping ultrasound exposure as low as possi-
ble, 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 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, an ultrasound system
provides controls that can be manipulated during the exam to optimize the
results of the exam.
The ability of the user to abide by the ALARA principle is important. Advances in
diagnostic ultrasound not only in the technology but in the applications of that
technology, have resulted in the need for more and better information to guide
the user. The output display indices are designed to provide that important infor-
mation.
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
index values, body size, location of the bone relative to the focal point, attenua-
tion in the body, and ultrasound exposure time. Exposure time is an especially
useful variable, because it is controlled by the user. The ability to limit the index
values over time supports the ALARA principle.
Applying ALARA
The system imaging mode used depends upon the information needed. 2D and
M-mode imaging provide anatomical information, while Doppler, Philips Color
Power Angio (CPA), and Color imaging provide information about blood flow. A
scanned mode, like 2D, CPA, or Color, disperses or scatters the ultrasonic energy
over an area, while an unscanned mode, like M-mode or Doppler, concentrates
ultrasonic energy. Understanding the nature of the imaging mode being used
allows the sonographer to apply the ALARA principle with informed judgement.
Additionally, the transducer frequency, system setup values, scanning techniques,
and operator experience allow the sonographer to meet the definition of the
ALARA principle.
Special care must be taken to enter the correct application when conducting an
exam, and to remain in that application throughout the course of that examina-
tion. In the future, HD11 XE may add some applications, such as ophthalmic appli-