L2 - Computed Radiography: Artifacts

Question 1

Artifact

Answer 1

It is used to describe any part of an image that does not accurately represent the anatomic structures present within the subject being evaluated.

Question 2

What are the different Image Acquisition Artifacts?

Answer 2

1. Twin Artifacts (Double Exposure)
2. Uncollimated Exposure
3. Delayed Scanning
4. Exposure through the Back of Cassette
5. Improper Grid-Usage; Moire Effect
6. Scatter Radiation
7. Care and Carelessness
8. Light Bulb Effect

Question 3

2 types of Computed Radiography Artifacts

Answer 3

1. Image Acquisition Artifacts

2. Image Processing Artifacts

Question 4

Twin Artifacts

Answer 4

• AKA Double Exposure
• Cause: It refers to the two subsequent exposure of the imaging plate, during inspiration and expiration that lead to the duplication of images.
• AEC: Automatic Exposure Control

Question 5

Uncollimated Image

Answer 5

• Cause: No use of collimation or improper use of collimation
• Collimation is a restrictor

Question 6

An increase in collimation results in what?

Answer 6

• narrower restrictor
• decrease of scatter radiation and exposed tissues
• increase in image quality

Question 7

A decrease in collimation results in what?

Answer 7

• wider restrictor

- increase of scatter radiation and exposed tissues

Question 8

Delayed Scanning

Answer 8

The delay between acquisition and processing of the image will lead to a decrease in image quality thus resulting in the fading of the image

• Cause: Delay in the processing of the image
• Solution: Prevent the delay of image processing.

Question 9

Exposure through the Back of the Cassette

Answer 9

• The back of the cassette is present in the image

- Cause: The first exposed part was the back of the cassette

Question 10

Inappropriate Exposure Factors

Answer 10

Has 2 types: Overexposure and Underexposure

Question 11

Overexposure

Answer 11

• Result: Irreversible darkening of the image because of too much xray transmitted
• Image look: too dark image.
• Too many x-ray transmitted and passed through the phosphor due to high technical factors

Question 12

Underexposure

Answer 12

• Result: Images appear grainy = Quantum Mottle

- Common in Hypersthenic Patients: Big physique

Question 13

Very bright white image

Answer 13

• High contrast
• Soft tissues are color white
• Too white due to low gray scale because of too little x-ray transmitted and passed through
• Solution: increase kVp, technical factors to go in the gray scale

Question 14

Flow of the things put to prevent high radiation exposure to patients

Answer 14

First: Filtration: for Xrays before reaching the patients, to reduce low energy xrays absorption that hits the patients

Second: Collimator

Third: Grid: absorbs Xrays that deviated after reaching the patient

Question 15

Scattered Radiation

Answer 15

Imaging plate are highly sensitive to radiation and the presence of scattered radiation reduces the quality of the image

Question 16

Care and Carelessness

Answer 16

Cause: improper handling of the cassettes and imaging plates

Result: kink marks = moon light artifacts

Question 17

Light Bulb Effect

Answer 17

Meaning: Artificial darkening of the lower and outer portions of an image

Cause: Entering of backscattered radiation into the PSP imaging plate from the patient’s bed.
Increase of exposure for the obese patients (not advisable) (yes, we need high technical factors for obese patients but you need to estimate it) or uncollimated X-ray beams. The increased exposure is due to the wide dynamic range and high sensitivity of the imaging plate

Solution: Lowering the kVp or by using precise collimation

Question 18

kVp

Answer 18

define the intensity/ energy of the x-ray photon. QUALITY

Question 19

mAs

Answer 19

define the amount of photons given to a patient. QUANTITY