Image Artifact (CTBC 9)

Question 1

Artifact is any _______ & may lead to _______.

Answer 1

Any distortion/error that doesn’t accurately represent area being imaged
May lead to misdiagnosis, loss of image info

Question 2

Sources of Artifact (3)

Answer 2

Incorrect Protocol Selection
Improper Positioning
Equipment Failure

Question 3

2 Broad categories of Artifacts

Answer 3

Patient Artifacts
Equipment Artifacts

Question 4

Streak Artifact

Answer 4

Abnormal streaking on image

Question 5

Patient Artifacts (are caused by) (2)

Answer 5

Something in Patient
Something in scan field (e.g., EKG lines)

Question 6

Equipment Artifacts (are caused by) _______E.g., (2)

Answer 6

Things outside scan field. E.g., broken detector, processing failure

Question 7

Beam Hardness

Answer 7

Average energy of photons in beam

Question 8

Beam hardness _______ as it passes through any material because the _______ energy photons are _______ first

Answer 8

Increases
Lower Energy
Attenuated First

Question 9

Beam Hardening Artifact appears as _______ and is especially common when _______

Answer 9

Dark or Light streaks radiating from dense object(s) in image
Especially common when dense objects adjacent to low-density materials

Question 10

Beam hardening is common in basilar fossa (of skull) when passing through _______ portions

Answer 10

Petrous portions

Question 11

Beam hardening common in pelvis between _______.

Answer 11

Femurs

Question 12

When arms are left down to the sides, resultant streaking is called

Answer 12

Beam Hardening

Question 13

Beam Hardening can generally be minimized with (2)

Answer 13

Special Software and Filters

Question 14

Most intense form of beam hardening

Answer 14

Metal Artifact

Question 15

Edge Gradient Artifact (2)

Answer 15

Mild form of beam hardening from areas of high contrast (e.g., ,bone-brain interface, fluid level b/w contrast & bowel gas)
Appears as streaks extending from area of high contrast

Question 16

Motion Artifact occurs when

Answer 16

From voluntary (swallowing/breathing) or involuntary (cardiac/bowel peristalsis) motion

Question 17

Motion Artifact typically appears as (2)

Answer 17

Blurring of Image
Streaks extending from areas of high density (e.g., bone)

Question 18

Misregistration

Answer 18

Misalignment of anatomy
(E.g., breathing during chest CT will cause same ribs to appear at different locations in the scan)

Question 19

Out-of-Field Artifact

Answer 19

White streaking artifact on the periphery of the patient occurring when the scanner assumes the (very-dense) edges of a patient are within the SFOV

Question 20

Partial Volume Averaging

Answer 20

Misrepresentation of anatomy d/t averaging of tissues into given slice which can morph or hide pathology–or cause normal anatomy to appear pathologic

Question 21

Artifact d/t failure of element within detector array appears as

Answer 21

Ring Artifact
Can also result from contrast on mylar window or on detector itself
Often corrected by running air cal

Question 22

Aliasing Artifact

Answer 22

Appears as series of evenly spaced streaks extending from object edges
Result of under-sampling/missing info
E.g., from fast rotation time or fast pitch that results in fewer projections

Question 23

Fan beam

Answer 23

Scan using only a few detector rows

Question 24

Cone beam

Answer 24

Scan using several detector rows

Question 25

Cone beam artifact

Answer 25

Distortion in shape of imaged objects resulting from use of wider beam using more detector rows (unlikely in modern scanners)

Question 26

Artifact presenting as a pattern of parallel streaks across the entire image (usually affecting one axial slice)

Answer 26

Tube arcing

Question 27

This occurs when the x-ray tube shorts d/t electron stream leaping from cathode to tube envelope (instead of to anode) & there is temporary loss of x-ray output

Answer 27

Tube arcing (electrons form an arc away from intended path)

Question 28

Artifact often corrected by running air cal

Answer 28

Ring Artifact

Question 29

Can result from contrast on mylar window or on detector itself

Answer 29

Ring Artifact