Chapter 21

Question 1

Artifact = Error in Imaging and includes reflections that are:

Answer 1

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

Question 2

Causes of artifact

Answer 2

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

Question 3

Hyperechoic:

Answer 3

tissues that appear brighter than normal

Question 4

Hypoechoic:

Answer 4

tissues that appear less bright than normal

Question 5

Anechoic:

Answer 5

an extreme form of hypoechoic meaning without echoes or echo free

Question 6

Isoechoic:

Answer 6

structures with equal echo brightness

Question 7

Homogenous:

Answer 7

tissue that has similar echo characteristics throughout

Question 8

Heterogenous:

Answer 8

tissue that has differing echo characteristics throughout

Question 9

6 imaging assumptions

Answer 9

-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

Question 10

Reverberation

Answer 10

-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

Question 11

Characteristics of Reverberation

Answer 11

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

Question 12

Comet Tail

Answer 12

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

Question 13

Shadow

Answer 13

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

Question 14

Edge Shadow

Answer 14

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

Question 15

Enhancement

Answer 15

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

Question 16

Focal Enhancement

Answer 16

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

Question 17

Mirror Image

Answer 17

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

Question 18

Crosstalk

Answer 18

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

Question 19

Speed Error

Answer 19

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

Question 20

Lobes

Answer 20

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

Question 21

Refraction

Answer 21

Occurs when a sound pulse changes direction during transmission

Question 22

Slice Thickness

Answer 22

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

Question 23

Lateral Resolution Artifact

Answer 23

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

Question 24

Axial resolution artifact

Answer 24

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

Question 25

Multipath Artifact

Answer 25

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

Question 26

Curved/Oblique Reflector Artifact

Answer 26

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

Question 27

Temporal Resolution Artifact

Answer 27

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

Question 28

Spatial Resolution Artifact

Answer 28

Factors that contribute to poor spatial resolution Fewer lines Analog Digital

Question 29

Range Ambiguity Artifact

Answer 29

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

Question 30

Contrast Resolution Artifact

Answer 30

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)

Question 31

Noise

Answer 31

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

Question 32

Speckle

Answer 32

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

Question 33

Clutter

Answer 33

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

Question 34

Translational artifact – motion artifact

Answer 34

Structure moves in and out of view