image characteristics & artifacts - ch 20

Question 1

what is hyperechoic?

Answer 1

parts of an image that are brighter than surrounding tissues

Question 2

hypoechoic?

Answer 2

portions of image that are not as bright as surrounding tissues

Question 3

anechoic?

Answer 3

without echoes

Question 4

isoechoic?

Answer 4

structures with equal echo brightness

Question 5

homogeneous?

Answer 5

portion of image that has similar echo characteristics throughout

Question 6

heterogeneous?

Answer 6

displays variety of diff echo characteristics within the image

Question 7

what are reverberations? (how do they occur what do they look like)

Answer 7

created when US ping pongs bw reflectors; multiple, equally spaced appears like a ladder, parallel to sound beam

Question 8

what is a comet tail? (how do they occur what do they look like)

Answer 8

small metal objects create these; single solid hyperechoic line, long echo, parallel to sound beam

Question 9

what is shadowing? (how do they occur what do they look like)

Answer 9

too much attenuation in structure above shadow; absence of anatomy, hypo or anechoic region

Question 10

what is edge shadowing?(how do they occur what do they look like) how to eliminate?

Answer 10

due to refraction and beam spreading along edge of curved reflector, hypoechoic; eliminated by spatial compounding

Question 11

enhancement? (how do they occur what do they look like)

Answer 11

too little attenuation in structure above artifact; hyperechoic foreground color

Question 12

mirror image?

Answer 12

duplicate structures located deeper that than true object

Question 13

propagation speed errors cause what?

Answer 13

reflector will be placed to shallow or too deep on the display; step-off or split

Question 14

refraction artifact?

Answer 14

second copy of true reflector appears side by side, occurs with oblique incidence

Question 15

what are side and grating lobes? what creates each?

Answer 15

extra acoustic energy is transmitted in directions other than the beam’s main axis. mechanical trans = side lobes array trans = grating lobes

Question 16

how can you fix side/grating lobes?

Answer 16

subdicing or apodization

Question 17

slice thickness artifact? (how do they occur what do they look like)

Answer 17

when beam has a greater width than the reflector called elevational resolution; fills in anechoic structures; fixed with 1 1/2 dimensional array and annular array transducers

Question 18

range ambiguity artifact? (how do they occur what do they look like)

Answer 18

created by reflection from structure located deeper than max imaging depth; fixed by imaging deeper or coded excitation