Lab Quiz

Question 1

What is the definition of Computed Radiography (CR)?

Answer 1

Uses a photostimulable phosphor (PSP) plate inside a cassette instead of film. After exposure, the cassette is placed in a CR reader, which uses a laser to stimulate the trapped electrons and convert them into light.

Question 2

What happens to the light produced in Computed Radiography (CR)?

Answer 2

The light is then converted into an electrical signal and digitized.

Question 3

What are the advantages of CR over Film Radiography?

Answer 3

• Can correct over/under-exposure
• Image can be digitally processed for enhancement
• No need for a darkroom

Question 4

What are the limitations of Computed Radiography (CR)?

Answer 4

• Lower spatial resolution due to light scatter within the plate
• Images can fade over time
• Scattered radiation can affect image quality

Question 5

What are the steps in the CR Imaging Process?

Answer 5

• Exposure: X-ray photons interact with the phosphor
• Storage: Energy is trapped in the PSP
• Scanning: A laser releases stored energy as visible light
• Digitization: The light is converted into an electrical signal

Question 6

What factors affect CR Image Quality?

Answer 6

• Spatial resolution (affected by laser beam size)
• Contrast resolution (depends on bit depth)
• Noise (caused by scatter radiation)
• Artifacts (due to incorrect processing)

Question 7

What is the definition of Digital Radiography (DR)?

Answer 7

Unlike CR, DR does not use cassettes. Instead, it has fixed detectors that send images directly to the computer.

Question 8

What are the two types of Digital Radiography (DR)?

Answer 8

• Direct (DDR)
• Indirect (IDR)

Question 9

Describe the Indirect Digital Radiography Process.

Answer 9

Uses a scintillator to convert X-rays into visible light. A photodiode (e.g., amorphous silicon) then converts the light into an electrical charge, which is processed and displayed as an image.

Question 10

What type of detectors are used in Indirect Digital Radiography Systems?

Answer 10

Indirect TFT (Thin Film Transistor) Flat Panel Detectors - Uses Cesium Iodide (Csl).

Question 12

What is used in Indirect CCD Flat Panels?

Answer 12

Gadolinium Oxysulfide (GOS)

GOS is cheaper but has lower resolution.

Question 13

What is an advantage of Indirect DR?

Answer 13

Faster readout compared to CR

Other advantages include less radiation needed and portable options available.

Question 14

What is a disadvantage of Indirect DR?

Answer 14

Lower resolution than Direct DR

Indirect DR is also more expensive than CR.

Question 15

What happens when Source to Image Distance (SID) increases?

Answer 15

Radiation dose decreases

This is explained by the Inverse Square Law.

Question 16

What effect does increasing kVp have on image contrast?

Answer 16

Reduces contrast

Higher kVp allows for higher penetration of X-rays.

Question 17

What is the 15% kVp Rule?

Answer 17

Increasing kVp by 15% doubles image brightness

This is similar to doubling mAs.

Question 18

What does mAs control?

Answer 18

The quantity of X-rays

Higher mAs results in a higher radiation dose and brighter image.

Question 19

Fill in the blank: Too high mAs leads to _______.

Answer 19

overexposure

Overexposure results in reduced contrast.

Question 20

Fill in the blank: The best balance for imaging is the optimal mAs setting to get the clearest image with the least _______.

Answer 20

radiation exposure

This ensures a clear image without unnecessary radiation.

Question 21

What type of questions should focus on definitions, advantages/disadvantages, and processes?

Answer 21

Multiple-Choice Questions (MCQs)

MCQs can include examples like materials used in indirect DR scintillators.

Question 22

True or False: Increasing SID results in a brighter image.

Answer 22

False

Increasing SID may lead to underexposure and a grainy image.

Question 24

What does the 15% kVp Rule state?

Answer 24

Increasing the kVp by 15% will double the image brightness, similar to doubling the mAs.

Question 25

How can kVp adjustments minimize patient radiation dose?

Answer 25

If kVp is increased, mAs can be reduced to maintain the same image density while lowering radiation exposure.

Question 26

What happens when kVp is decreased by 15%?

Answer 26

It halves the brightness, requiring a doubling of mAs to compensate.

Question 27

What is the primary difference between Direct and Indirect Digital Radiography (DR)?

Answer 27

Direct DR converts X-rays directly into an electrical charge using a photoconductor, while Indirect DR first converts X-rays into visible light using a scintillator.

Question 28

What is a photoconductor used in Direct DR?

Answer 28

Amorphous selenium.

Question 29

What is a scintillator commonly used in Indirect DR?

Answer 29

Cesium Iodide (CsI).

Question 30

How does a photodiode function in Indirect DR?

Answer 30

It converts visible light into an electrical signal.

Question 31

What are the advantages of Direct DR?

Answer 31

Higher resolution images.

Question 32

What are the advantages of Indirect DR?

Answer 32

Faster and cheaper.

Question 33

How does increasing mAs affect image quality?

Answer 33

Increases the number of X-rays produced, leading to a brighter image with better visibility of details.

Question 34

What are the consequences of too much mAs?

Answer 34

Overexposure, loss of contrast, and difficulty in distinguishing structures.

Question 35

Fill in the blank: Increasing mAs results in _______.

Answer 35

higher radiation dose to the patient.

Question 36

Fill in the blank: The optimal mAs should be selected to balance image _______ and radiation exposure.

Answer 36

brightness.