.png "X-ray Film | Types of X-ray Film (Part 3)")
Introduction
As we have previously known, X-rays are a modern and innovative technology used in medicine, especially in the field of medical diagnosis. One of the old methods of X-ray imaging is the use of X-ray film technology. X-ray film records information related to the body (tissues) through which X-rays pass, thus greatly helping in diagnosing and treating the patient's problem. In the previous article (Part 2) we talked about the basic components of X-ray films as well as their layers, explaining how silver halide crystals are prepared and how the latent image is produced in addition to the additional components of the film. In this article we will talk about the types of X-ray film, their applications, what is meant by X-ray film speed, as well as single-coated and double-coated X-ray film, and the packaging and handling of radiographic films.
Types of X-ray Film
I. According to their USES:
a) Intraoral films: These films are used inside the mouth to capture detailed images of the teeth and surrounding structures.
1- Periapical films: Used to show the entire tooth and the surrounding bone.
- Children: Smaller size film appropriate for children's mouths.
- Anterior adult: Slightly larger film used for the front teeth of adults.
- Standard adult: Regular size film for general adult use.
2- Occlusal films: Used to show the floor of the mouth and the palate. These films are larger and capture a broader area than periapical films.
3- Bitewing films: Used to show the crowns of the upper and lower teeth simultaneously, often used to detect cavities between teeth.
b) Extraoral films: These films are used outside the mouth to capture images of larger areas such as the jaw and skull. Examples include panoramic and cephalometric films.
II. According to SPEED:
a) Slow film: Requires longer exposure time to produce an image.
1- Speed A.
2- Speed B.
3- Speed C.
b) Fast film: Requires less exposure time, reducing patient radiation exposure.
1- D - Ultra speed.
2- E - Ekta speed.
3- F - Ultra-Ekta speed.
c) Hyper speed G: Provides the fastest exposure time among X-ray films.
III. According to the EMULSION LAYER:
a) Single-coated: Has emulsion on only one side of the film.
b) Double-coated: Has emulsion on both sides of the film, providing greater sensitivity and reducing exposure time.
IV. According to PACKAGING:
a) Single film packet: Contains one film per packet.
b) Double film packet: Contains two films per packet, allowing for duplicate records or reducing the need for retakes.
Types of X-ray Film - Based on their Application
1) Screen Films:
Screen films are the most frequently used type of film. They are sensitive to the blue light emitted by intensifying screens as well as the direct action of X-rays. These films are utilized in cassettes that contain intensifying screens, and they operate at high speed.
2) Non-screen / Direct exposure films:
Non-screen or direct exposure films have a thicker coat of emulsion and are used without an intensifying screen, relying primarily on the action of X-rays. These films are four times faster than screen films, requiring only one-quarter of the exposure. Due to their thick emulsion, they must be manually processed. These films are used in limb radiography, for detecting intra-ocular foreign bodies, and in dental applications with intra-oral cardboard.
3) Mammography film:
Mammography film is specifically designed with a single coating and fine grain to ensure high image quality. It operates at a slow speed, which contributes to its ability to produce high-contrast images. This type of film is intended for use with a single intensifying screen. The combination of these features is crucial for delivering a minimal radiation dose to the glandular tissue while maintaining diagnostic effectiveness.
4) Duplicating Film:
Duplicating film is used to create copies of radiographs. To duplicate a radiograph, the original cassette is placed into a special cassette where the opaque front has been replaced with clear glass. A piece of special duplicating film, with its emulsion side facing down, is then placed onto the radiograph, and the lid is closed. The film is exposed to create a duplicate image.
Speed of X-ray Film
The speed of X-ray film refers to the amount of radiation necessary to create a radiograph with sufficient density. Films that are classified as slow require more exposure to achieve the desired image density, while fast films need less exposure. Several factors influence the speed of X-ray film, including the size of the crystals, the shape of the grains, and the thickness of the emulsions. Larger crystals and thicker emulsions generally contribute to slower film speeds, while smaller crystals and thinner emulsions result in faster film speeds. These characteristics are crucial in medical imaging and diagnostics, as the appropriate film speed ensures the best balance between image quality and patient exposure to radiation.
Single Coated and Double Coated X-ray Film
Detailed explanations of comparison between single-coated and double-coated X-ray films based on the provided characteristics:
1- Emulsion Layer,
- Single Coated: The emulsion, which contains the light-sensitive silver halide crystals, is only on one side of the film.
- Double Coated: The emulsion is applied on both sides of the film, effectively doubling the amount of light-sensitive material.
2- Patient Radiation Dose,
- Single Coated: Higher radiation dose is needed to achieve sufficient image density since the emulsion is only on one side.
- Double Coated: Requires less radiation to achieve the same image density because the emulsion on both sides increases the film's sensitivity.
3- Radiographic Detail,
- Single Coated: Provides higher radiographic detail because there's no parallax effect, resulting in sharper images.
- Double Coated: Lower radiographic detail due to the parallax effect, which can cause blurring of fine details.
4- Average Gradient (G),
- Single Coated: Typically has a lower average gradient, meaning it is less responsive to small changes in exposure.
- Double Coated: Higher average gradient, making the film more responsive to changes in exposure and providing greater contrast.
5- Parallax Effect,
- Single Coated: Does not experience the parallax effect because there is only one layer of emulsion.
- Double Coated: The parallax effect can occur because the image forms on two separate layers, potentially causing slight misalignment and blurring.
6- Contrast,
- Single Coated: Generally lower contrast compared to double-coated films.
- Double Coated: Higher contrast due to the increased amount of emulsion, making differences in tissue density more pronounced.
Radiographic Film Packaging Options
Radiographic film is available in several packaging options to suit different needs. The simplest form is individual sheets in a box. These sheets must be loaded into a cassette or film holder in a darkroom to protect them from light exposure. Available in various sizes, the sheets can come with or without interleaving paper. Interleaved packages include a layer of paper separating each sheet, which is removed before loading the film into the holder. Many users find interleaving paper helpful for separating the sheets and providing some protection against scratches and dirt during handling.
Light-Tight Envelope Packaging
Industrial X-ray films are also offered in light-tight envelopes, allowing exposure from either side without removing the film from the protective packaging. These envelopes have a rip strip for easy removal of the film in the darkroom for processing. This packaging eliminates the need to load film holders in the darkroom and keeps the film protected from finger marks and dirt until processing.
Roll Film Packaging
Radiographic film can also be purchased in rolls, enabling radiographers to cut the film to any desired length. The ends of the packaging are sealed with electrical tape in the darkroom. This packaging is particularly advantageous for applications like the radiography of circumferential welds and the examination of long joints on aircraft fuselages. Long lengths of film provide significant economic benefits as they allow the examination of large areas with a single exposure by wrapping the film around the structure and positioning the radiation source on the axis inside.
Envelope Packaged Film with Lead Oxide Screens
Envelope-packaged film can also be bought with the film sandwiched between two lead oxide screens. These screens reduce scatter radiation at energy levels below 150 keV and function as intensification screens at levels above 150 keV.
Film Handling
Film handling is crucial to prevent physical damage like pressure, creasing, buckling, and friction. When loading films into semi-flexible holders with external clamping devices, it's essential to ensure uniform pressure. Uneven pressure, such as from a film holder pressing against high spots like an underground weld, can lead to desensitized areas in the radiograph. This caution is especially critical when using envelope-packed films.
To avoid marks caused by moist or chemically contaminated fingers, as well as crimp marks, large films should always be held by the edges and allowed to hang freely. Keeping clean towels nearby encourages frequent and thorough hand drying. Envelope-packed films help mitigate these issues until they are opened for processing.
Additionally, it's important to avoid pulling films rapidly from cartons, exposure holders, or cassettes. Such care reduces the risk of circular or tree-like black markings in radiographs caused by static electric discharges. These precautions are essential for maintaining the quality and integrity of radiographic films throughout handling and processing.
Conclusion
X-ray films remain essential tools in medical imaging, offering a range of types tailored to specific diagnostic needs. From intraoral films for dental applications to specialized mammography films, each type serves distinct purposes in capturing detailed images crucial for accurate diagnosis. The classification by speed, emulsion layer, and packaging further highlights the versatility and advancements in X-ray film technology, ensuring both high image quality and minimized patient radiation exposure. Proper handling and packaging techniques underscore the importance of maintaining film integrity throughout the imaging process, crucial for reliable diagnostic outcomes in medical practice.
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