Terason t3000, Руководство пользователя

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Chapter 5 - Working With Scan Modes Using Spectral Doppler Image Controls
Terason t3000 / Echo Ultrasound System User Guide 112
Adjusting the Steering Angle
When using Spectral Doppler, be aware of the Doppler angle-to-flow (the angle between
the axis of the ultrasound beam and the plane that the blood flows in). When the
ultrasound beam is perpendicular to the flow (90º angle-to-flow), an absent or confusing
color pattern displays, even when the flow is normal. An adequate Doppler angle-to-flow
is required to obtain useful Spectral Doppler information. In most instances, the more
nearly parallel to the flow the Doppler beam is (the lower the angle-to-flow), the better the
received signal. Angles less than 60º provide the best quality Spectral Doppler.
Electronic steering is useful when the flow is at a poor angle to the Doppler beam.
However, it is often also necessary to press on one end of the transducer or the other to
improve the Doppler angle-to-flow.
Electronic steering is only available with flat linear-array transducers (the 7L3, 12HL7,
and 12L5). This option does not display with any other transducers. Curved linear and
phased array transducers are not capable of electronic steering, and depending on the
clinical situation, may require that you press down on one corner of the transducer to
obtain an adequate angle to flow.
The steering angle does not directly affect the calibration of the velocity scale.
To select a different steering angle, select an angle from the menu.
Steering Angle Menu
You can only use this control when viewing a live image. When an image is frozen, you
cannot change the setting.
You can also adjust the steering angle by typing a slash ( / ). When you type this character,
the Terason software highlights the Steering Angle value and you can use the left and right
arrow keys to change the value. If you press the key twice quickly, the Terason software
highlights the Correction Angle.
Adjusting the Correction Angle
To obtain accurate velocities, you must maintain Doppler angles of 60º or less. It is often
necessary to press on one end of the transducer or the other to improve the Doppler angle-
to-flow.
In the Terason Ultrasound System, the velocity display in centimeters per second is shown
only in the correction angle range b70º and –70º. At angles greater than 70º, the
error in the velocity calculation is too large, and the velocity scale is converted to
frequency, independent of the correction angle. The flow-direction indicator still shows on
the window, for reference.
To adjust the correction angle, click the right arrow to increase the angle, or the left arrow
to decrease the angle.