18 Image Characteristics + Artifacts

Question 0

What are ultrasound artifacts?

Answer 0

Errors in imaging

Not real, missing reflectors, improper brightness, improper shape, improper size, improper position

Question 1

List image characteristics.

Answer 1

Hyperechoic
Hypoechoic
Anechoic
Isoechoic
Homogeneous
Heterogeneous

Question 2

What are causes of artifacts?

Answer 2

Violation of assumptions
Equipment malfunction or design
Physics of ultrasound
Interpreter error
Operator error

Question 3

What are the six basic assumptions of imaging systems?

Answer 3

1. Sound travels in a straight line
2. Sound travels directly to a reflector and back
3. Sound travels exactly 1540 m/s
4. Reflections arise from structures positioned along the beam’s
5. Intensity of the reflections is related to the scattering characteristics of the tissue
6. The imaging plane is extremely thin

Question 4

What are reverberations?

Answer 4

Multiple echoes appearing on the display as a result of ultrasound ping-ponging between two reflectors

Question 5

What are some characteristics of reverberations?

Answer 5

Multiple
Equally spaced
Parallel to the sound beam
Deeper and along a straight line

Question 6

What is comet tail or ringdown artifact?

Answer 6

A solid line directed downward, merged reverberation

Question 7

What are characteristics of comet tail or ringdown artifact?

Answer 7

Single, solid hyperechoic line
Long echo
Parallel to second beam
A reverb with the ‘space’ squeezed out

Question 8

What is shadowing artifact?

Answer 8

Hypoechoic region that appears distal to a hyperechoic structure

Question 9

What is edge shadow or shadowing by refraction?

Answer 9

Refraction at the edge of a circular structure

Question 10

What is enhancement artifact?

Answer 10

Deeper areas appear brighter on display - hyperechoic, because attenuation is less when sound travels through a medium with a lower attenuation rates than soft tissue

Question 11

What is a mirror image artifact?

Answer 11

A second copy of a reflector if sound bounces off of a strong reflector

Question 12

What is a propagation speed error?

Answer 12

A step off, split or cut from incorrect # of reflections on scan and improper depths

Question 13

What is a refraction artifact?

Answer 13

When sound changes direction after striking a boundary

Degrades lateral resolution

Question 14

What is side lobe artifact?

Answer 14

Extra acoustic energy transmitted in directions other than the beam’s main axis in a mechanical or single crystal transducer

Question 15

What is a grating lobe artifact?

Answer 15

Extra acoustic energy caused from arrays

Question 16

What is subdicing?

Answer 16

Reduction or curing of grating lobe artifact by dividing each element into even smaller pieces

Question 17

What is apodization?

Answer 17

Reduction of grating lobes by exciting the subdiced elements with different voltages

Question 18

What is slice thickness artifact?

Answer 18

When the beam has a greater width than the reflector causing elevational resolution - reflections produced by structures above or below the ideal imaging plane appear on the image

Question 19

What is range ambiguity artifact?

Answer 19

Very deep reflections from a previous pulse arrive at a transducer after the next pulse was created
Cured by lowering the PRF (imaging deeper)

Question 20

What is cross talk artifact?

Answer 20

Seen on Doppler only

Special form of a mirror image where the Doppler spectrum appears above and below the baseline

Question 21

What are 2 causes of cross talk?

Answer 21

Doppler gain set too high

Incident angle near 90° when flow is at focus