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Physics > Chapter 21 > Flashcards

Chapter 21 Flashcards

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1
Q

Artifact = Error in Imaging and includes reflections that are:

A

Not Real
Not seen on the image
Not of correct size or shape
Not of correct brightness

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2
Q

Causes of artifact

A

Violation of assumptions
Equipment malfunction or poor design
The physics of ultrasound
Operator error

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3
Q

Hyperechoic:

A

tissues that appear brighter than normal

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4
Q

Hypoechoic:

A

tissues that appear less bright than normal

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5
Q

Anechoic:

A

an extreme form of hypoechoic meaning without echoes or echo free

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6
Q

Isoechoic:

A

structures with equal echo brightness

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7
Q

Homogenous:

A

tissue that has similar echo characteristics throughout

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8
Q

Heterogenous:

A

tissue that has differing echo characteristics throughout

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9
Q

6 imaging assumptions

A

-Sound travels in a straight line
-Sound travels directly to a reflector and back
-Sound travels in soft tissue at exactly 1,540 m/s
-Reflections arise only from structures positioned in the beam’s main axis
-The imaging plane is very thin
-The strength of a reflection is related to the characteristics of the tissue creating the reflection

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10
Q

Reverberation

A

-appears on the display as multiple, equally spaced echoes
-caused by the bouncing of the sound wave between a strong reflector and the probe or two strong reflectors positioned parallel to the beam

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11
Q

Characteristics of Reverberation

A

Appears in multiples
Appears equally spaced
Located parallel to the sound beam
Located at ever increasing depths

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12
Q

Comet Tail

A

Closely spaced reverberations merge i.e. “the spaces are squeezed out”
Solid hyperechoic line directed downward
AKA ring down artifact

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13
Q

Shadow

A

Hypoechoic or anechoic region extending downward from a very strong attenuating medium

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14
Q

Edge Shadow

A

Special form of shadowing that appears as a hypoechoic region extending along the edge of a curved reflector
AKA shadowing by refraction

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15
Q

Enhancement

A

Appears as a hyperechoic region beneath tissues with abnormally low attenuation (cystic or fluid filled structures)

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16
Q

Focal Enhancement

A

Special form of enhancement in which a side-to-side or horizontal region of an image is hyperechoic or brighter
AKA focal banding

17
Q

Mirror Image

A

Image shows mirror like reflector or line with real reflector on one side shallower and the false replica on other side deeper
Deeper vessel is artifact

18
Q

Crosstalk

A

Same spectral Doppler display above and below baseline
Flow appears bidirectional when it is unidirectional

19
Q

Speed Error

A

Occurs when sound travels thru a medium at a speed other than that of soft tissue
Reflector is placed at incorrect depth

20
Q

Lobes

A

Unintentional side beams
reflector will appear twice, side by side, at the same depth

21
Q

Refraction

A

Occurs when a sound pulse changes direction during transmission

22
Q

Slice Thickness

A

is when structures in front of or behind the “assumed” thin imaging plane appear in the plane
Hollow structures like cysts appear partially filled in

23
Q

Lateral Resolution Artifact

A

Occurs when a beam is wider than the distance between two reflectors that are located side by side or perpendicular to the beam
Two side by side objects appear as one on the display, or a narrow reflector appears wider

24
Q

Axial resolution artifact

A

Occurs when a long pulse strikes two closely spaced structures, one in front of the other or parallel to the sound beam
Only one longer reflection appears on the display

25
Q

Multipath Artifact

A

Sound beams hit a reflector, some beams return directly to probe, others take an extended path

26
Q

Curved/Oblique Reflector Artifact

A

When a sound beam strikes a curved or oblique reflector, some of the reflected sound may be directed away from the probe

27
Q

Temporal Resolution Artifact

A

When frame rates are too low, we are unable to precisely position a moving structure from instant to instant; can miss brief event on color flow

28
Q

Spatial Resolution Artifact

A

Factors that contribute to poor spatial resolution
Fewer lines
Analog
Digital

29
Q

Range Ambiguity Artifact

A

occurs when a reflection from a structure deeper than the maximum imaging depth is inadvertently received by the probe.

30
Q

Contrast Resolution Artifact

A

Fewer shades of gray or few shades devoted to low level signals can provide for poor contrast resolution (lose the ability to discern between similar adjacent tissues)

31
Q

Noise

A

appears as small amplitude or spurious reflections and results from many sources such as electrical interference and signal processing

32
Q

Speckle

A

Is a form of noise, arises from small amplitude sound waves interfering with each other close to the transducer
Appears as grainy false tissue texture

33
Q

Clutter

A

Noise around the baseline on the Doppler spectrum due to low Doppler shifts off tissue being displayed, best eliminated with wall filter

34
Q

Translational artifact – motion artifact

A

Structure moves in and out of view

Physics (25 decks)

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