Showing posts with label Film. Show all posts
Showing posts with label Film. Show all posts

Types of Film

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In addition to screen-film, direct-exposure film, sometimes called nonscreen film and special application film (such as that used in mammography, video recording, duplication, subtraction, cineradiography, and dental radiology), is available. Each has particular characteristics that become more familiar to the radiologic technologist with use.


Screen-Film

As was previously stated, screen-film is the most widely used IR in radiology. Several characteristics must be considered when one is selecting screen-film: contrast, speed, spectral matching, anticrossover/antihalation dyes, and requirement for a safelight.

Table 11-1 Types of Film Used in Medical Imaging

Type
Emulsions
Characteristics
Applications
Intensifying screen
Two
Blue or green sensitive
General radiography
Laser printing
Single with antihalation backing
Matches laser used (about 630 nm)
Laser printers attached to CT, MRI, ultrasound, etc.
Copy or duplicating
Single with antihalation backing
Pre-exposed to Dmax
Duplicating radiographs
Dental
Two packed in sealed envelope
Has lead foil to reduce back scatter
Dentistry
Radiation monitoring
Two packed in sealed envelope
One emulsion can be sloughed off to increase OD scale
Radiation monitoring
Dry transfer
One
Thermally sensitive
“Dry” printers



Non- Screen Film

Non screen film also known as direct exposure film is film that does not require the application of intensifying screen. This is most commonly used in mammography.






















Radiographic Film

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Construction of the Radiographic Film
1.) Base
-          Supports the emulsion 150-300 mm thick, semi rigid lucent and made of polyester, the foundation of the Radiographic Film. Its primary purpose is to provide a rigid structure unto which the emulsion can be coated. It is flexible and fracture-resistant. It maintains the film shape and size during use and processing to limit extortion. It is flexible. It provides region structure.
Ø  Dye
-          Is added to tint the film blue to reduce eye strain.

Ø  Dimensional Stability
-          is the property of the base to maintain its size and shape.
Four Types of Base
1.) Glass Plate – the original film base
2.) Cellulose Nitrate – becomes a substitute of the glass plate and highly flammable.
3.) Cellulose Triacetate – not flammable and safety base
4.) Polyester – more resistant to warping from age and stronger and thinner than cellulose triacetate.
Ø  Emulsion – the heart and the most important part of the x-ray film. This is where the x-rays and light photons from IS interacting and transfer information. Consist of homogenous mixture of gelatin and silver halide crystals and coated evenly in 3-5 mm thick.
Ø  Gelatin – provides mechanical support for the silver halide crystals.
Ø  Silver Halide Crystals – the active ingredient of the emulsion. 98% of the crystal is Ag halide crystal and 2% is Ag iodide.
Atomic Number of the following:
Bromine = 35, Silver = 47, Iodine = 53, Gelatin and Base = 7
Ø  Contaminant – is the imperfection of the arrangement of crystals
3.) Adhesive Layer – a thin coating of material between the emulsion and base, it ensures the uniform adhesion between them. It allows the emulsion and base to maintain proper contact during use and processing.
4.) Overcoat Layer – the protective covering of the gelatin. It protects the emulsion from scratches, pressure, and contamination during handling, processing and storage. It also allows a rough manipulation of film before exposure.

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