Screen Film Radiology
Screen Film Radiology
Screen Film Radiology
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3. The <strong>Screen</strong>-<strong>Film</strong> Cassette<br />
Cassette<br />
v Light-tight and ensures screen<br />
contact with film<br />
v Front surface - carbon fiber<br />
v ID flash card area on back<br />
1 or 2 Intensifying <strong>Screen</strong>s<br />
v Convert x-rays to visible light<br />
v Mounted on layers of<br />
compressed foam (produces<br />
force)<br />
Sheet of film<br />
v Register the x-ray distribution<br />
v Chemically processed<br />
v Storage and display<br />
c.f. Bushberg, et al. The Essential Physics of<br />
Medical Imaging, 2 nd ed., p 148.<br />
4. Characteristics of Intensifying <strong>Screen</strong>s<br />
v <strong>Film</strong> relatively insensitive to x-rays, requires a lot of x-ray energy to<br />
produced a properly exposed x-ray film<br />
v Patient receives a large dose<br />
v To reduce dose and exposure times, screens are used<br />
v <strong>Screen</strong>s made of scintillating material: phosphor<br />
v When x-rays interact with phosphor, visible or UV light is emitted<br />
Light emitted darkens the film<br />
v → <strong>Screen</strong>-film detectors are considered an Indirect detector<br />
Using film-screen film screen versus film only reduces<br />
radiation dose to patient by a factor of 50!<br />
7<br />
8<br />
4
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