Biological Safety Safety
Lumify Ultrasound System 39
Philips Healthcare 4535 618 58571_A/795 * MAY 2016
For example, peripheral vascular intensity levels are not recommended for fetal exams. Some
systems automatically select the proper range for a particular application, while others require
manual selection. Ultimately, the user has the responsibility for proper clinical use. The
ultrasound system provides both automatic (default) settings and manual (user-selectable)
settings.
Output power has direct impact on acoustic intensity. Once the application has been
established, the power control can be used to increase or decrease the intensity output. The
power control allows you to select intensity levels less than the established maximum. Prudent
use dictates that you select the lowest output intensity that is consistent with good image
quality.
Indirect Controls
The indirect controls are those that have an indirect effect on acoustic intensity. These controls
affect imaging mode, pulse repetition frequency, focus depth, pulse length, and transducer
selection.
The choice of imaging mode determines the nature of the ultrasound beam. 2D is a scanning
mode; Doppler is a stationary or unscanned mode. A stationary ultrasound beam concentrates
energy in a single location. A moving or scanned ultrasound beam disperses the energy over an
area and the beam is concentrated on the same area for a fraction of the time as that of an
unscanned mode.
Focus of the ultrasound beam affects the image resolution. To maintain or increase resolution
at a different focus requires a variation in output over the focal zone. This variation of output is
a function of system optimization. Different exams require different focal depths. Setting the
focus at the proper depth improves the resolution of the structure of interest.
Transducer selection indirectly affects intensity. Tissue attenuation changes with frequency.
The higher the transducer operating frequency, the greater the attenuation of the ultrasonic
energy. A higher transducer operating frequency requires more output intensity to scan at a
deeper depth. To scan deeper at the same output intensity, a lower transducer frequency is
required. Using more gain and output beyond a point, without corresponding increases in
image quality, can mean that a lower frequency transducer is needed.
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