GE H48681XB, Руководство по обслуживанию

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5.1.1.3 Color Doppler Modes
Color Doppler is used to detect motion presented as a two-dimensional display. There are following
applications of this technique:
•
Color Flow Mode (C) - used to visualize blood flow velocity and direction
•
Power Doppler (PD) - used to visualize the spatial distribution of blood
•
Bi-Directional Angio (HD-Flow) - used to visualize flow direction with spatial resolution and low artifact
visibility
•
Tissue Doppler (TD) - used to visualize tissue motion direction and velocity
5.1.1.3.1 Color Flow Mode
A real-time two-dimensional cross-section image of blood flow is displayed. The 2D cross-section is
presented as a full color display, with various colors being used to represent blood flow (velocity, variance,
power and/or direction). Often, to provide spatial orientation, the full color blood flow cross-section is overlaid
on top of the grayscale cross-section of soft tissue structure (2D echo). For each pixel in the overlay, the
decision of whether to display color (Doppler), 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.
Blood velocity is the primary parameter used to determine the display colors, but power and variance may
also used. 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. Color
flow can be used in combination with 2D and Spectral Doppler modes as well as with 3D mode.
5.1.1.3.2 Power Doppler
A real-time two dimensional cross-section of blood flow is displayed. The 2D 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 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 and Spectral Doppler modes as well as with
3D mode.
5.1.1.3.3 Bi-Directional Angio (HD-Flow Mode)
Directional Power Doppler is a Power Doppler mode incorporating the flow direction (much like Color
Doppler) into the displayed image. The focus of the settings for Directional Power Doppler is for high spatial
resolution and low artifact visibility, allowing vessels to be seen with less blooming and finer detail.
5.1.1.3.4 Tissue Doppler
The Tissue Color Doppler Imaging is used for color encoded evaluation of heart movements. The TD image
provides information about tissue motion direction and velocity.
5.1.1.4 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 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 and Color Flow modes.
Components and Functions (Theory)
Voluson E-Series Service Manual
KTD106657 Revision 2
5-7