US Physics Chapter 21

Question 1

Describe what reverberation artifact is and what causes it

Answer 1

Two strong evenly spaced reflectors with multiple lines like a ladder or Venetian blinds

Question 2

Comet tail or ring down artifact what causes it

Answer 2

Closely spaced reverberations merge usually reflecting surfaces with very high propagation speed (such as mechanical heart valve) or can arise by resonance form small structures such as gas bubbles after bombarded by sound pulse

Question 3

What causes shadow artifact?

Answer 3

Hypoechoic or anechoic region extending from highly attenuating structure

Question 4

What causes edge shadow

Answer 4

Special form of shadowing that you see with hypo echoic region extending from edge of curved reflector.

Question 5

What causes “enhancement artifact”

Answer 5

Opposite of shadowing - results from tool little attenuation. Locate beneath structure w/ abnormally low attenuation like gallbladder or cystic structure

Question 6

What is another name for focal enhancement

Answer 6

Focal banding

Question 7

What is cause of focal enhancement

Answer 7

Its a band that results form increased intensity at the focus

Question 8

What causes mirror image artifact? Where does reflection appear?

Answer 8

A mirror object deeper than the true object due to reflection off a mirror plane

Question 9

What does propagation speed error look like and what causes it?

Answer 9

When sound is transmitted at a speed other than that of the speed of sound in soft tissue 1540 m/s a step off can appear.

Question 10

Which direction does displacement occur if speed of sound is slower in object (such as breast implant) with propagation speed error

Answer 10

Step off shows tissue deeper on display than it actually is.

Question 11

Another name for propogation speed error artifact

Answer 11

range error artifact

Question 12

What is another name for section thickness artifact

Answer 12

partial volume artifact

Question 13

Whats another name for lateral resolution artifact

Answer 13

Point spread artifact

Question 14

What causes lateral resolution artifact

Answer 14

If two objects are less than the width of the sound beam they may appear to merge into one

Question 15

What causes axial resolution artifact

Answer 15

when two structures are closer than 1/2 the spatial pulse length.

Question 16

Where along beam is lateral resolution artifact least likely to occur

Answer 16

at focus

Question 17

What types of pulses are least likely to cause axial resolution artifact

Answer 17

Transducers that create short pulses (higher frequency and less ringing)

Question 18

What causes multipath artifact

Answer 18

Sound pulses glance off a second structure away from primary structure and take longer to get back to receiver.

Question 19

What is seen with curved or oblique reflector artifact?

Answer 19

Some reflected sound may be directed away from the transducer by a curved reflector. You get varying intensity of similar echogenic structure just from sound hitting boundary at different angles.

Question 20

What is noise?

Answer 20

Small amplitude echoes resulting form multiple things including electrical interference signal processing and spurious reflections. More likely to affect low level hypo echoic areas than bright echogenic regions

Question 21

What is speckle?

Answer 21

Results form constructive (in phase) and destructive (out of phase) interference of wavelets. Causes face detail like grainy tissue like appearance.

Question 22

What reduces speckle artifact?

Answer 22

spatial compounding