Film and Digital Imaging

Question 1

Emulsion found where? importance? describe it

Answer 1

part of the film

o Two-sided
 More sensitive to radiation – but also lowers resolution
 Trade off between film speed/ how sensitive and with resolution
o Sensitive to x-rays and visible light

Question 2

advantage of double sided emulsion

Answer 2

o Since it is double sided and thus more sensitive to radiation – the radiation exposure required to make an image is LESS

Question 3

is latent image visible or invisible

Answer 3

invisible

- the chemical change has taken place, but it cant be seen until the film is developed

Question 4

process of emulsion

Answer 4

• Has silver hylaide crystals sensitive to the radiation
• Radiation reacts with crystals and release electrons and BIND WITH SILVER IONS
  o Now neutral silver atoms
• Silver halide crystals
• “Latent Image” formation (invisible until film is developed)
• X-ray radiation or visible light → Release electrons
• e- + Ag+ → Ag

Question 5

more sensitive implication on speed

Answer 5

more sensitive also means faster

• but always a trade off with resolution
• if faster the resolution will be less (reduction in resolution with increased speed/ sensitivity)

Question 6

spectral matching

Answer 6

emitting certain wavelength that should match the film sensitivity
o Emission of screen must match the absorption of film
o Screen = sensitivity of film

Question 7

Film processing steps (1-5) which are most important

Answer 7

1. develop
2. rinse
3. fixer
4. wash
5. dry

focus on develop and fixer phases

Question 8

Develop phase

Answer 8

Converts any exposed AgBr crystals to metallic silver grains (dark)
Reduces Ag in crystals (Ag+) to neutral Ag
If left too long, even unexposed crystals are reduced (chemical fogging – image too dark)

Question 9

Throughout the day, your film radiographs are getting lighter and lighter. How do you correct this?

Answer 9

replenish developer solution (with respect to film)

Question 10

development solution temperature effect

Answer 10

if too cool wont develop as well and get a lighter image

Question 11

development solution temperature effect

Answer 11

if too cool wont develop as well and get a lighter image

Question 12

If the film is not exposed to x-rays at all, the optical density will be zero?

Answer 12

• FALSE  it will be light but always some degree of density

but it will be very close

Question 13

exposure

Answer 13

• # of photons reaching the film
• Increasing mA or time
• Increasing kVp
• Reducing the distance between focal spot and film

Question 14

high contrast is what grey scale

Answer 14

short grey scale

higher contrast better for differentiating

(low contrast = long grey scale)

Question 15

film latitude

Answer 15

lower contrast – wider latitude

important when want to record tissues of greatly varying densities

Question 16

films with a wide latitude have what contrast?

Answer 16

lower contrast