Chapter 21 Artifacts

Question 1

What is an error in imaging or something that doesn’t belong called?

Answer 1

Artifact

Question 2

Portions of an image that are brighter than surrounding tissues, or that appear brighter than normal?

Answer 2

Hyperechoic

Question 3

Portions of an image that are not as bright as surrounding tissues, or tissues that appear less bright than normal?

Answer 3

Hypoechoic

Question 4

An extreme form of hypoechoic, meaning entirely without echoes (echo free)

Answer 4

Anechoic

Question 5

Describes structures with equal echo brightness

Answer 5

Isoechoic

Question 6

a portion of tissue or an image that has similar echo characteristics throughout

Answer 6

Homogeneous

Question 7

a portion of tissue or an image that has differing echo charateristics throughout

Answer 7

Heterogeneous

Question 8

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

Answer 8

Reverberation

Question 9

Artifact that . .

• appears in multiples
• appears equally spaced
• located parallel to the sound beam’s main axis
• located at ever increasing depths

Answer 9

Reverberation

Question 10

With reverberations, which of the echoes are real if any?

Answer 10

First two

Question 11

This appears as a solid, hyperechoic line directed downward, created when closely spaced reverberations merge (aka, Ring down artifact)

Answer 11

Comet tail

Question 12

artifact that . . .

• appears as a single long hyperechoic echo
• located parallel to the sound beam’s main axis

Answer 12

Comet tail

Question 13

This appears as a hypoechoic or anechoic region extending downward from a very strong attenuating medium

Answer 13

Shadow

Question 14

Artifact that . .

• results from too much attenuation
• hypo or anechoic
• located beneath the structure with abnormally high attenuation
• prevents visualization of true anatomy on the scan

Answer 14

shadow

Question 15

Is shadowing related to the speed of sound in a medium?

Answer 15

No

Question 16

This appears as a hypoechoic region extending along the edge of a curved reflector. The sound beam refracts at the edge resulting in an intensity drop

Answer 16

Edge Shadow (Shadowing by refraction)

Question 17

Artifact that . . .

• results when the beam spreads after striking a curved reflector
• hypo or anechoic
• extends downward from the curved reflector’s edge parallel to the beam
• prevents visualization of true anatomy

Answer 17

Edge shadow (shadowing by refraction)

Question 18

This appears as a hyperechoic region beneath tissues with abnormally low attenuation

Answer 18

Enhancement

Question 19

In enhancement related to the speed of sound in the medium?

Answer 19

NO

Question 20

Name the artifact:

• Hyperechoic
• results from too little attenuation
• located beneath the structure with abnormally low attenuation

Answer 20

Enhancement

Question 21

This appears when side to side region of the image appears brighter than tissues at other depths

Answer 21

Focal enhancement (focal banding)

Question 22

What is most often the cause of focal enhancement?

Answer 22

A TGC pod is set too high

Question 23

Name the artifact:

• a hyperechoic side to side region
• results from increased intensity at the focus

Answer 23

Focal enhancement ( focal banding)

Question 24

This appears when sound reflects off of a strong reflector and is redirected toward a second structure, causing a replica to incorrectly appear on the image

Answer 24

Mirror image

Question 25

In the case of mirror images, which one is the artifact?

Answer 25

Deeper image is the artifact

Question 26

Name the artifact: - a second copy of a true reflector - copy appears deeper than the true reflector - a bright reflector, the mirror, lies on a straight line between the artifact and the transducer - true reflector and artifact are equal distances from the mirror

Answer 26

Mirror image

Question 27

This appears as a mirror image artifact on a spectral doppler display

Answer 27

Crosstalk

Question 28

This appears when a sound wave propagates through a medium at a speed other than that of soft tissue (1.54Km/s): the correct number of reflectors are displayed, but at incorrect depths

Answer 28

Speed error (Range error artifact)

Question 29

- go return time is too short - System assumes reflectors are close to the transducer - reflectors are too shallow - distances are underestimated (too small)

Answer 29

Medium's speed is Faster than that of soft tissue

Question 30

- go return time is too long - system assumes reflectors are far from the transducer - reflectors are too deep - distances are overestimated (too large)

Answer 30

Medium's speed is slower than that of soft tissue

Question 31

Name the artifact: - Correct number of reflectors - improper depth - appears as a step off

Answer 31

Speed error (range error artifact)

Question 32

This appears when sound energy is transmitted in a direction other than the sound beam's main axis, degrading lateral resolution

Answer 32

Lobe artifacts - side lobes - grating lobes

Question 33

Side lobes

Answer 33

one crystal

Question 34

Grating lobes

Answer 34

arrays

Question 35

Name the artifact: - a second copy of the true reflector - artifact and the true reflector are located side by side at the same depth

Answer 35

Lobe artifacts - side lobes (one crystal) - grating lobes (arrays)

Question 36

What are two methods for reducing lobe artifacts?

Answer 36

Subdicing | Apodization

Question 37

Dividing each crystal into small pieces

Answer 37

Subdicing

Question 38

Differential excitation: inner elements receive higher voltages while outer elements receive lower voltages

Answer 38

Apodization

Question 39

This appears when a sound pulse changes direction during transmission, degrading lateral resolution

Answer 39

Refraction

Question 40

Name the artifact: - a second copy of the reflector - the copy is side by side or at the same depth as the true reflector

Answer 40

Refraction

Question 41

This appears when reflections from structures above or below the assumed imaging plane appear in the image, or hollow structures appear filled in

Answer 41

Slice thickness artifact/ elevational resolution

Question 42

How can slice thickness artifact/ elevational resolution problems be reduced?

Answer 42

1 1/2 dimensional array transducers (matrix) which create thinner imaging planes

Question 43

This appears when a beam is wider than the distance between two reflectors that are located side by side. In this case, the two objects appear as one reflection

Answer 43

Lateral resolution

Question 44

This appears when a long pulse strikes two closely spaced structures, where one is in front of the other. Only one reflection will appear if the structures are closer together than 1/5 the SPL

Answer 44

Axial Resolution artifact

Question 45

What type of transducers reduce axial resolution artifacts?

Answer 45

Higher frequency

Question 46

This appear when sound pulses glance off a second structure on the way to of from the primary reflector, resulting in a transmit path length different from the receive path length and subtle, non-specific errors

Answer 46

Multipath artifacts

Question 47

This appears when a sound beam strikes a curved or oblique reflector, causing some of the reflected sound to be directed away from the transducer

Answer 47

Curved/ oblique reflectors

Question 48

Name the artifact: - Reflections are absent or - Reflections appear too weak or - Reflections appear different than other similar reflecting boundries

Answer 48

Curved /oblique reflectors

Question 49

This appears as a result of low frame rates and causes less accurate positioning of reflectors in motion

Answer 49

Temporal resolution artifacts

Question 50

This appears as a result of low line density causing less detail in the image

Answer 50

Spatial resolution artifact

Question 51

When the image is in analog format for display on a CRT how is spatial resolution determined?

Answer 51

Number of scan lines fer frame (more the better)

Question 52

When the image is in digital format, how is spatial resolution determined?

Answer 52

Pixel density (more the better)

Question 53

Closely packed sound pulses, image exhibits great detail, spatial resolution is exceptional

Answer 53

High line density

Question 54

Each pixel is large and the spatial resolution degrades

Answer 54

Low pixel density

Question 55

Wider gaps between the sound pulses, the image exhibits less detail, spatial resolution is poor

Answer 55

Low line density

Question 56

Each pixel is small resulting in a detailed image with excellent spatial resolution

Answer 56

High pixel density

Question 57

When a reflecting structure is located deeper than the imaging depth of the image. This reflector is placed on a shallow location on the image

Answer 57

Range ambiguity artifact

Question 58

Range ambiguity is eliminated by increasing the ________

Answer 58

PRP

Question 59

Longer PRP means ________ imaging and decreased PRF

Answer 59

Deeper

Question 60

Small amplitude echoes resulting from many sources including electrical interference, signal processing and spurious reflections. Most likely affects low-level hypoechoic regions

Answer 60

Noise

Question 61

A form of noise arising from small amplitude sound waves interfering with each other; Most likely to appear close to the transducer - grainy appearance that is not directly related to the actual biologic tissue

Answer 61

Speckle

Question 62

A form of noise associated with Doppler

Answer 62

Clutter

Question 63

A high-tech solution for reducing an image's noise content: | selectively distinguish meaningful reflections from noise, thereby improving signal to noise ratio

Answer 63

Harmonics

Question 64

What are the six assumptions of imaging systems

Answer 64

1. Sound travels in a straight line 2. Sound travels directly to a reflector and back 3. Sound travels in soft tissue at exactly 1540m/s 4. Reflections arise only from structures positioned in the beams 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 reflections

Question 65

Anatomic reflectors are absent on image

Answer 65

- shadowing - shadowing by refraction - lateral resolution - Axial resolution

Question 66

Anatomic reflector appears multiple times on image. Artifact positioned deeper than the true anatomy

Answer 66

- Comet tail - Ring down - Reverberation - Mirror image

Question 67

Anatomic reflector appears multiple times on image. Artifact displaced to the side of the true anatomy

Answer 67

Refraction Side lobe Grating lobe

Question 68

Anatomic reflectors appear with abnormal brightness

Answer 68

Enhancement (hyperechoic) Banding (hyperechoic) Shadowing (hypoechoic) Shadowing by refraction (hypoechoic)

Question 69

Anatomic structures appear at incorrect depth

Answer 69

Speed errors | Range ambiguity

Question 70

Anatomic structures appear in the incorrect imaging plane

Answer 70

Slice or section thickness

Question 71

Anatomic structures do not correspond to echoes on the image

Answer 71

acoustic speckle | Multipath