Artifact

Question 1

Name five types of artifact.

Answer 1

Not real
Not seen on the image
Not the correct size or shape
Not in the correct position
Not a correct brightness

Question 2

What is artifact?

Answer 2

Simply an error in the ultrasound imaging.

Question 3

What are four causes of artifact?

Answer 3

Violation of one of the six assumptions
Equipment malfunction or poor design
The physics of ultrasound
Operator error

Question 4

What are the six basic assumptions?

Answer 4

1) Sound travels in a straight line.
2) Sound travels directly to a reflector and back.
3) Sound travels at exactly 1540 m/s in soft tissue
4) Reflections only from structures positioned in the beams main axis
5) Image plane is very thin
6) Strength of reflection is relative to the characteristic of tissue creating this reflection.

Question 5

Define hyperechoic:

Answer 5

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

Question 6

Define hypoechoic:

Answer 6

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

Question 7

Define anechoic:

Answer 7

An extreme form of hypoechoic, meaning entirely without echoes. Echo free.

Question 8

Define Isoechoic:

Answer 8

Describes structures with equal echo brightness.

Question 9

Define homogenous:

Answer 9

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

Question 10

Define heterogeneous:

Answer 10

Good portion of tissue or an image that has different echo characteristics throughout.

Question 11

Name some key types of artifacts:

Answer 11

Reflection, reverberation, shadowing, comet tail, side lobe, mirror image, speed error, grating lobe.

Question 12

Define reverberation:

Answer 12

Multiple or equally spaced echoes. Created by the bouncing of sound waves between two very strong reflectors position parallel to the ultrasound beam.

Question 13

What part of the reverberation artifact are real?

Answer 13

The first two reflections are real those after that are not true anatomical structures.

Question 14

Define comet tail:

Answer 14

Reverberation without the spacing. Ring down effect. When reflectors are in a medium with a very high propagation speed, metallic heart valve for example. A gas bubble would be another example.

Question 15

Define shadow:

Answer 15

Anechoic or hypoechoic region below a strong attenuating medium. No sound goes on so structures deep cannot be identified.

Question 16

Define edge shadow:

Answer 16

A special form of shadow found extending along the edge of the curved reflector.

Question 17

Define enhancement:

Answer 17

Hyperechoic region below tissue with it normally low attenuation. Number of reflectors is correct but some are overly bright. A fluid filled cyst is a good example of this effect where the fluid within does not attenuate the transmitted sound causing the deeper structure to appear brighter than normal.

Question 18

Define mirror image:

Answer 18

Sound reflects off a strong reflector and is redirected towards another structure. The redirection causes a replica of the structure to incorrectly appear on the image. Reflector is always on a straight line between the transducer and artifact. Artifact is place deeper than the real structure.

Question 19

Define refraction:

Answer 19

Sound changes direction during transmission. Has the sound strikes a boundary obliquely and media on either side of the boundary have different propagation speeds, the sound beam will bend or refract. Causes A copy of the true reflector to appear latterly have the same depth. This is different from the mirror artifact which appears deeper than the original.

Question 20

How will a side lobe artifact manifest?

Answer 20

Side lobe artifacts appear as false images from sides superimposed on the main image.

Question 21

What are the two main side effects caused by ultrasound energy with regard to bioeffects?

Answer 21

Heat (SPTA) and cavitation.

Question 22

What does the acronym ALARA mean?

Answer 22

As low as reasonably achievable.