Physics 2 - Module 6 ARTIFACTS*

Question 1

What are the 4 things that artifacts are a result of?

Answer 1

1. Malfunctioning equipment
2. Defective recording device
3. Improper operation of equipment
4. Acoustic properties of tissues and propagation of sound waves

Question 2

What are the 4 assumptions about how sound propagates made by the machine?

Answer 2

1. All tissue has the same acoustic velocity
2. The sound beam always travels straight
3. Echo strength indicates organ echogenicity only
4. The distance to each reflector equals the round trip time

Question 3

What are the 4 categories of artifacts?

Answer 3

1. Not real
2. Missing
3. Improper location
4. Improper brightness, shape, size, etc

Question 4

What are the 2 main groups of artifacts?

Answer 4

1. Propagation group

2. Attenuation group

Question 5

Objects <1/2 SPL apart in the axis of the beam appear as a single echo

Answer 5

Axial resolution artifact

Question 6

Also called point spreading. Reflector appears smeared across the screen

Answer 6

Lateral resolution artifact

Question 7

Also known as volume averaging, can account for the filling in of anechoic structures with false debris.

Answer 7

Slice thickness artifact

Question 8

How to assist with acoustic speckle?

Answer 8

Persistence

Question 9

Constructive and destructive interference that creates heterogenous areas of brightness due to scatter

Answer 9

Acoustic speckle artifact

Question 10

Reflection of sound between the transducer and a strong interface

Answer 10

Reverberation

Question 11

How to correct reverberation?

Answer 11

Harmonics

Question 12

The type of reverberation seen with metal, calcium, cholesterol, etc

Answer 12

Comet tail

Question 13

What type of reverberation is seen in gas?

Answer 13

Ring down. Appears as dirty shadowing

Question 14

Duplication of an object due to odd angle and strong reflector.

Answer 14

Mirror image

Question 15

This artifact is the result of the assumption that the beam travels in a straight line and is corrected by getting more perpendicular to the structure of interest

Answer 15

Multipath artifacts

Question 16

Shadows at the edges of strong, curved reflectors

Answer 16

Edge shadow

Question 17

Why does edge shadowing occur?

Answer 17

Refraction. The beam changes direction when angle of incidence is not perpendicular

Question 18

Appears as lateral duplication of an echo due to refraction of the beam by a strong interface

Answer 18

Refractive duplication

Question 19

The echo is falsely allocated laterally from its true position due to bending of the beam

Answer 19

Refractive malposition

Question 20

Linear echogenic bands due to radial mode vibration

Answer 20

Side/grating lobe artifacts

Question 21

How to correct side lobes?

Answer 21

Insulator ring

Question 22

How to correct for grating lobes?

Answer 22

Apodization and sub-dicing

Question 23

Misallocation of a reflector more prox or distal to its actual location.

Answer 23

Propagation speed error

Question 24

Rare in 2D, common in doppler. Echoes appear closer to the transducer than they actually are.

Answer 24

Range ambiguity.

Question 25

What causes range ambiguity artifact?

Answer 25

PRF too high. Sending a second pulse before the first one returns

Question 26

Name 7 propagation artifacts

Answer 26

- Axial resolution artifact - lateral resolution artifact - section thickness artifact - acoustic speckle - reverberation - mirror image - multipath - refraction - grating/side lobes - speed error - range ambiguity

Question 27

What are the 4 attenuation artifacts?

Answer 27

- shadowing - enhancement - focal enhancement - edge shadowing

Question 28

A lack of echoes beneath a highly attenuating structure

Answer 28

Shadowing

Question 29

Posterior brightness to structures that are less attenuating

Answer 29

Enhancement

Question 30

False brightening to a particular area of the image at the level of the focal zone. Corrected with TGCs

Answer 30

Focal enhancement

Question 31

Name 5 doppler artifacts

Answer 31

1. Aliasing 2. Slice thickness 3. Reverberation 4. Mirror image 5. Flash or clutter 6. Noise 7. Refraction

Question 32

Multiple flows seen within one flow envelope due to beam width

Answer 32

Doppler slice thickness

Question 33

Reverberation on a stone that produces a mosaic of colour

Answer 33

Twinkle artifact (a doppler reverberation artifact)

Question 34

Appears as a false vessel or spectral doppler flow on both sides of the baseline

Answer 34

Doppler mirror image

Question 35

How to correct for doppler mirror image?

Answer 35

Decrease gains, decrease angle of insonation (it’s too close to 90)

Question 36

Low level echoes of colour seen in the tissue as a result of movement

Answer 36

Doppler flash or clutter

Question 37

What is used to eliminate doppler flash/clutter

Answer 37

Filter presets on the machine

Question 38

Doppler gains set too high causing the colour to blossom outside of the vessel

Answer 38

Doppler noise

Question 39

What are the artifacts associated with malfunction of equipment?

Answer 39

1. Electronic interference 2. Faulty software 3. Faulty scan converter 4. Faulty equipment - malfunctioning crystal - cracked damping material - defective recording device - improper transducer shielding

Question 40

False location of a structure lateral to its actual position

Answer 40

Refractive malposition

Question 41

How would one correct for artifacts related to lateral resolution?

Answer 41

Scan in the near zone