GE LOGIQ E9 Service Manual page 212

GE H
EALTHCARE
D 5180263-100, R
IRECTION
5-2-6-3-1 Power Doppler
A real-time two dimensional cross-section of blood flow is displayed. The 2D (B-Mode) (B-Mode) cross-
section is presented as a full color display, with various colors being used to represent the power in
blood flow echoes. Often, to provide spatial orientation, the full color blood flow cross-section is overlaid
on top of the gray scale cross-section of soft tissue structure (2D (B-Mode) (B-Mode) echo). For each
pixel in the overlay, the decision of whether to display color (Doppler power), gray scale (echo)
information or a blended combination is based on the relative strength of return echoes from the soft-
tissue structures and from the red blood cells. A high pass filter (wall filter) is used to remove the signals
from stationary or slowly moving structures. Tissue motion is discriminated from blood flow by assuming
that blood is moving faster than the surrounding tissue, although additional parameters may also be
used to enhance the discrimination. The power in the remaining signal after wall filtering is then
averaged over time (persistence) to present a steady state image of blood flow distribution. Power
Doppler can be used in combination with 2D (B-Mode) (B-Mode) and Spectral Doppler modes as well
as with 4D mode.
5-2-6-4 Pulsed (PW) Doppler
PW Doppler processing is one of two spectral Doppler modalities, the other being CW Doppler. In
spectral Doppler, blood flow is presented as a scrolling display, with flow velocity on the Y-axis and time
on the X-axis. The presence of spectral broadening indicates turbulent flow, while the absence of
spectral broadening indicates laminar flow. PW Doppler provides real time spectral analysis of pulsed
Doppler signals. This information describes the Doppler shifted signal from the moving reflectors in the
sample volume. PW Doppler can be used alone but is normally used in conjunction with a 2D (B-Mode)
(B-Mode) image with an M-line and sample volume marker superimposed on the 2-D image indicating
the position of the Doppler sample volume. The sample volume size and location are specified by the
operator. Sample volume can be overlaid by a flow direction cursor which is aligned, by the operator,
with the direction of flow in the vessel, thus determining the Doppler angle. This allows the spectral
display to be calibrated in flow velocity (m/sec.) as well as frequency (Hz). PW Doppler also provides
the capability of performing spectral analysis at a selectable depth and sample volume size. PW Doppler
can be used in combination with 2D (B-Mode) (B-Mode) and Color Flow modes.
5-2-6-5 Continuous Wave (CW) Doppler
Continuous Wave Doppler systems use two crystals, one to send and one to receive the echoes.
The transmitter inputs a continuous sinusoidal wave. The receiver detects the shift.
An audible sound is created and recorded by either an analog recorder or spectral analyzer. Spectral
analysis separates the signal into individual components and assigns a relative importance.
The benefits of CW Doppler include high sensitivity to low velocities and detection of high velocities
without aliasing. Although CW Doppler cannot distinguish between the sending and receiving signals or
extraneous echoes, nor does CW Doppler produce a precise image like Pulsed Wave Doppler.
5-2-6-6 Other Modes
4D: The LOGIQ E9 Ultrasound System may be used to acquire multiple, sequential 2D (B-Mode) (B-
Mode) images which can be combined to reconstruct a three dimensional image. These 4D images are
useful in visualizing three-dimensional structures, and in understanding the spatial or temporal
relationships between the images in the 2D (B-Mode) (B-Mode) sequence. The 4D image is presented
using standard visualization techniques, such as surface or volume rendering.
For more information on Volume Navigation and Contrast Imaging, refer to the Basic User Manual.
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Section 5-2 - LOGIQ E9 description
LOGIQ E9 S M
ERVICE ANUAL