P7.1 - Film, Screens, and Cassettes

Cassette

- Holds the film and protects it from physical damage and light exposure

- Holds the screens and protects them from physical damage

Backwards

Cassettes cannot alter an image or show up on images unless they are _____

Plastic

Cassettes are usually made of _____

Reduce patient exposure/dose

What is the purpose of screens?

Screens

_____ convert x-ray photons to visible light photons (amplify the number of photons)

Base

_____ of screen

Reflective layer

_____ of screen

Phosphor layer

_____ of screen

Protective layer

_____ of screen

Phosphors

Give off light when stimulated (luminescence)

Fluorescence

Gives light off right away (conventional x-ray)

Phosphorescence

Stores energy and glows later (CR digital x-ray)

- Photoelectric absorption of x-ray photon

- Resulting electron cascade produces visible light

Why do cassettes glow?

Film

_____ is being replaced by the digital receptor system

Visible light

Radiographic film is most sensitive to _____

Polyester

What base is used for film?

Blue

_____ dye is added to the polyester base to ease eye-strain of the reader

Supercoat

Protective layer

Film emulsion

How does a film capture an image?

90-99%

Silver bromide (AgBr) percentage in gelatin

1-10%

Silver iodide (AgI) percentage in gelatin

Sensitivity speck

_____ is key to image formation

Latent image

Image on film before developing (can't see it)

Ag+ to Ag

Exposure to photons causes reaction: _____

- Photon frees electrons (ionizing radiation)

- Electrons collect at sensitivity speck

- Negative electrons attract positive Ag ions

- Ag ion grabs electron, becomes elemental silver

Explain the reaction of Ag+ to Ag