Screen Characteristics pt 2

Question 1

What affects speed?

Answer 1

1. Intrinsic speed factors
2. Extrinsic speed factors

Question 2

What is an intrinsic speed factors?

Answer 2

refers to how intensifying screen is manufactured

Question 3

What are Intrinsic speed factors characteristics?

Answer 3

1. Phosphor composition
2. Phosphor thickness
3. Crystal size
4. Phosphor concentration
5. Reflective layer
6. Light absorption dye

Question 4

What is Phosphor composition?

Answer 4

Calcium tungstate vs. rare earth

Question 5

What is Conversion efficiency of phosphor composition?

Answer 5

the ability of the screen to convert x-ray energy into light energy

• Calcium tungstate= 5%
• Rare Earth = 20%

Question 6

Name four reasons rare earth is better over calcium tungstate screens.

Answer 6

1. Shorter exposure times
2. Lower technical factor
3. Increases tube life
4. Higher conversion efficiency

Question 7

What is the effect of phosphor thickness?

Answer 7

increasing the phosphor layer thickness increases screen speed

• slow speed and high speed

Question 8

What is the effect of crystal size?

Answer 8

increasing the crystal size increases speed

Question 9

What is the effect of phosphor concentration?

Answer 9

increasing the concentration or number of phosphor crystal increases speed

Question 10

What is the effect of the reflective layer?

Answer 10

the presence of the reflective layer increases speed. Isotropic light photons are redirected towards the film

Question 11

What is the effect of light absorbing dye?

Answer 11

• when added to phosphors, controls the spread (diffusion) of light photons
• detail is increased, but speed is sacrificed