Ch. 21 Artifacts

Question 1

5 types of artifacts

Answer 1

-not real
-seen on the image
-incorrect shape or size
-incorrect position
-incorrect brightness

Question 2

Causes of Artifacts

Answer 2

-violation of assumptions
-equipment malfunction or poor design
-the physics of ultrasound
-operator error

Question 3

Image Characteristics

Answer 3

-hyperechoic
-hypoechoic
-anechoic
-isoechoic
-homogeneous
-heterogeneous

Question 4

Hyperechoic

Answer 4

portions of an image that are brighter then surrounding tissues

Question 5

Hypoechoic

Answer 5

portions of an image that are not as bright as surrounding tissues, tissues that are less bright than normal

Question 6

Anechoic

Answer 6

entirely without echo or sonolucent

Question 7

Isoechoic

Answer 7

structures with equal echo brightness

Question 8

Homogeneous

Answer 8

portion of tissue or an image that has similar echo characteristics throughtout

Question 9

Heterogeneous

Answer 9

portion of tissue or an image that has differing echo characteristics throughtout

Question 10

Six assumptions of imaging systems

Answer 10

1. sound travels in a straight line
2. sound travels directly to a reflector and back
3. sound travels in soft tissue at exactly 1,540 m/s
4. reflections arise only from structures positioned in the beam’s main axis
5. the imaging plane is very thin
6. the strength of a reflection is related to the characteristics of the tissue creating the reflection

Question 11

Artifacts appear when

Answer 11

these six assumptions are not true

Question 12

When corrective measures are taken, artifacts often

Answer 12

vanish

Question 13

Reverberation

Answer 13

appears as multiple, equally spaced echoes caused by the bouncing of the sound wave between two strong reflectors positioned parallel to the ultrasound beam

Question 14

Which assumptions does reverberation break?

Answer 14

Assumption #2, sound travels directly to a reflector and back

Question 15

Characteristics of reverberation

Answer 15

-appear in multiples
-appear equally spaced
-are located parallel to the sound beam’s main axis
-are located at ever-increasing depths

Question 16

Reverberation artifacts places too many

Answer 16

reflections on the image

Question 17

Reverberations resemble what?

Answer 17

a ladder or Venetian blind

Question 18

With reverberations the first two reflections are real the rest are artifacts.

Question 19

Reverberation is diagnostic.

Question 20

Comet Tail also know as

Answer 20

ring down artifact

Question 21

Comet tail

Answer 21

is reverberation with the spaces squeezed out appears as a solid hyper echoic line directed downward

Question 22

Comet tail artifact is created when

Answer 22

Closely spaced reverberations merge

Question 23

When are comet tail’s most likely to appear?

Answer 23

When the reflecting surfaces are located in a medium with a very high propagation speed, such as a mechanical heart valve.
-(when a sound wave bounces back and forth between two very closely spaced objects)

Question 24

Comet tail breaks which assumption?

Answer 24

Assumption #2, sound travels directly to a reflector and back

Question 25

Characteristics of comet tail

Answer 25

-appears as a single long hyperechoic echo -is located parallel to the sound beam's main axis

Question 26

Shadow

Answer 26

appears as a hypoechoic or anechoic region extending downward from a highly attenuating structure.

Question 27

shadows are the same color as

Answer 27

the images background

Question 28

When does shadowing occur?

Answer 28

shadows appear when the attenuation is higher in the tissue above the shadow than in the surrounding tissue

Question 29

shadowing prevents

Answer 29

the display of true anatomic structures

Question 30

Shadow breaks which assumption?

Answer 30

Assumption 6, the strength of a reflection is related to the characteristics of tissue creating the reflection.