Quatech Audio/Video Capture USB 2.0 Spezifikationen PDF herunterladen (Seite 371)

z.one ultra and z.one ultra sp OPERATOR MANUAL 15-5

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• Check the placement of the ECG pads on the patient and ensure connectivity

of all leads.

• Inspect the integrity of the individual ECG lead wires, connections, and

attachment at the connector of the main ECG cable harness.

• Disconnect the ECG connector from the front of the SmartCart and then

reconnect firmly.

• If system still fails to operate ECG, contact ZONARE Technical Support.

Acoustic

Artifacts

The transducer adds its own signature to the echo information in the form of beam

width effects, axial resolution limitations, and frequency characteristics. The

control choices made by the sonographer that affect amplification, signal

processing, and echo signal display can lead to significant differences in the

displayed appearance of echo data. Following is a brief discussion of acoustic

artifacts. An understanding of the physical basis for the production of signals

displayed on ultrasound images is helpful in minimizing artifacts on images and

interpreting the results of studies.

An artifact is an echo displayed in a different position from its corresponding

reflector in the body. Artifacts can also be caused by intervening tissue properties.

Artifacts can originate from external noise, reverberations, multi-path reflections,

or misadjusted equipment. They can also come from the ultrasonic beam

geometry and unusual changes in beam intensity. Artifacts and their

manifestations are listed below, and following are some definitions of various

artifacts.

• Added objects displayed as speckle, section thickness, reverberation, mirror

image, comet tail, or ring down

• Missing objects due to poor resolution

• Incorrect object brightness due to shadowing or enhancement

• Incorrect object location due to refraction, multi-path reflections, side lobes,

grating lobes, speed error, or range ambiguity

• Incorrect object size due to poor resolution, refraction, or speed error

• Incorrect object shape due to poor resolution, refraction, or speed error

Acoustic saturation occurs when received signals reach a system's

high-amplitude limit. At that point the system becomes unable to distinguish or

display signal intensities. At the point of saturation, increased input will not

increase output.

Aliasing occurs when the detected Doppler frequency exceeds the Nyquist limit.

It is characterized on the spectral display by the Doppler peaks going off the

display, top or bottom, and then continuing on the other side of the baseline. On

the Color display an immediate change in color from one Nyquist limit to the other

is seen.

Comet tail is a form of reverberation artifact produced when two or more strong

reflectors are close together and have a high propagation speed. In this case,

sound does not travel directly to a reflector and back to the transducer; and a

strong linear echo appears at the reflector and extends deeper than the reflector.

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