Research Paper
Film/screen combination & properties
Eduardo Longa
Radiation Protection and Radiobiology
Professor : Dr. Yolanda Acebo
Florida National University
07/12/2020
Radiographic film and intensifying screens are designed to:
Complement each other
To produce the highest-quality image with the lowest patient radiation dose
The film/screen combination is housed
Cassette
Film changer
Film/screen combination
Film/screen combinations are available from RS 20 to RS 1,200
Film and screens must be matched to each other to achieve diagnostic-quality images.
Mismatching of film and screens often increases patient dose.
Qualities considered
Speed
Resolution
Contrast
Latitude
SPEED
Term used to describe an imaging system's sensitivity to x-ray exposure
Depends on:
The thickness of the layer of phosphor or silver halide
The crystal/phosphor size
The efficiency of the crystal/phospor in emitting or capturing photons
Crystal/phosphor concentration
RESOLUTION
The recorded detail, sharpness and resolution are measured as:
Line pairs per mm (lp/mm or cycles per mm),
Line spread function (LSF)
Modulation transfer function (MTF)
contrast
Primarily the contrast of the film, although intensifying screens exhibit contrast.
Higher contrast is achieved when lower kVp can be used due to higher speed screens if often overlooked.
Rare-earth phosphors often exhibit slightly higher contrast
latitude
The exposure range of techniques that give a good diagnostic image:
Primarily dependent on the latitude of the film - directly related to the contrast.
Narrow latitude film/screen systems exhibit high contrast.
High speed film/screen systems tend to have lower resolution - decreased detail.
Selecting FILM/SCREEN
Considers the various film and screen characteristics.
Choose a film/screen combination to match the clinical need:
E.g.
Abdo / pelvis: Sensitive film-screen, reduced dose, some loss of detail.
Chest: Single phosphor / UV screens improves detail
Mammo: Single phosphor / Single emulsion high resolution film
FORMULAS IN FILM/SCREEN COMBINATIONS
Sensitivity in mR =
mAs 2 =
MTF =
11
References
Radiographic receptors. (n.d.). In Partnership with Institutions. https://www.sprawls.org/ppmi2/FILMSCR/
Carlton, R. R., & Adler, A. M. (2012). Principles of radiographic imaging: An art and a science. Cengage Learning.
Screen film radiography - FRCR physics notes. (n.d.). Google Sites. https://sites.google.com/site/frcrphysicsnotes/screen-film-radiography