Medical Film

Everything there is to know about a medical film

A medical film is a transparent and blue-tinted sheet made from a gelatinous emulsion with radiation-sensitive silver halides such as silver chloride and silver bromide. This emulsion differs from ordinary non-medical films with its unique characteristics of X-rays and gamma rays. The emulsion base coat has layers on both sides, about 0.0005 inches thick. The speed could increase by doubling the emulsion on both sides, which doubles the radiation sensitivity. On the other side, having emulsion on only one side gives greater details to the image. The thickness of the emulsion layers is low, so that processes like drying and fixing are easy and fast to perform.

The imaging process occurs when the X-ray beams strike the crystals of the radio-sensitive silver halide of the emulsion, liberating some of the halide ions, captured by free Ag ions. This ion exchange produces a latent image, which then becomes the precursor to the scan. The final step is applying a chemical solution to the gelatin layers, accelerating the exposed crystals' reduction process, which creates the final image.

History of the medical film

In 1895, Wilhelm Conrad Roentgen discovered X-rays when he observed a fluorescent glow while working on a cathode-ray tube. The tube included negative electrodes with a glass envelope encapsulating them. 

Roentgen concluded that the emitted rays from the tube could pass through materials in the laboratory room. Later that same year, he concluded it could pass human tissue. One year after Roentgen's invention, in 1896, Otto Walkhoff established the very first dental radiography. 

Indications to use a medical film

The radiography field's main goal is to generate high-quality imaging that shows the greatest possible details in the image, thus helping the physician in the proper diagnosis of conditions. This quality is achievable by monitoring different radiographic factors with one of the essential factors in the quality of the image being the type of medical film used in displaying the examination result.

The X-ray sheet's primary use is to display the radiographic images by X-ray scan units, which helps visualize body structures and diagnose conditions. Various types of machines use this material for printing visual scan, amongst which are:

  • Plain X-ray

Traditionally, the medical X-ray images displayed on a photographic film needed special processing before reviewing them. The plain X-ray imaging produces high-resolution images in a fast, easy, and cost-effective way. The average examination time is about 10 minutes, and there are no special pre-examination requirements. The radiologist optimizes the type and amount of X-rays to the part of the body under examination, the tissue type, and its size. The final examination imaging displays on the radiographic sheet, which is made and customized, especially for this function.

  • Panoramic Dental X-ray

This X-ray's performance is in a dental setting using a significantly small amount of ionizing radiation to capture a section in the teeth (intraoral) or the entire jaw in one image (extra-oral). This scanning procedure helps to diagnose and assess the oral structure's condition and determine the treatment approach. The panoramic X-ray is commonly preferred over conventional X-ray for its ability to visualize the tooth positioning and detect bone abnormalities in higher quality and more straightforward procedure approaches. This is the scan used to plan long-term treatment like the installation of braces, dental implants, and dental extraction.

The intraoral medical film is made as a double-layered emulsion, with high sensitivity to radiographic beams, so it requires less radiation to create an image. The examination is a direct exposure procedure for higher resolution imaging. The medical film used in this process works with one or two sheets, a black paper, and moisture-proof wrapper protection. 

Alternative instruments

The alternative to using a medical film in diagnostic radiography is the digital imaging system. The concept of digitizing the display of examination images minimizes the use of a traditional X-ray film and optimizes storage, transfer, and medical diagnostic data. The system used to convert data is called Analog to Digital Converted (ADV). This device takes data from the X-ray receptor, performing a quantization process where data converts to digital pixels. 

Precautions

While handling the medical film, it should be protected by avoiding physical scratches and friction and ensuring the uniformity of the pressure when used. To prevent contamination with processing chemicals, avoid direct contact with the moisture or fingers. The sheets should be drawn from the package gently to avoid the formation of circular black marks mostly from electric discharges.

General specifications of a medical film

The standard medical film should have significant characteristics that determine the quality of the display. These characteristics are mostly the sensitivity, the latitude of the sheet, the average gradient, and the system resolution. After these determinants, other conditions like the safelight sensitivity, the base tint, and the sheet granularity are considered secondary characteristics that affect the overall performance.

Base material: Gelatin Emulsion

Radiosensitive material: Silver Halide crystals (silver chloride or silver bromide)

Thickness: 0.0005 Inches

protective layer: gelatin

Automatic Processor. This equipment manages film processing. In contrast to the traditional manual processing, the automatic system enhances the produced images' quality while reducing the total processing time. Several variables, such as the temperature, the chemicals, and the mechanical elements, should be checked in assessing the processor performance.

How They Work 

Firstly, while shooting the X-ray beams, the light strikes the medical film's grains, containing sensitive silver halide emulsion. After the exposure, the Br-ions liberate to be received by the Ag+ ions. This process produces a latent image, an elementary state of the scan that couldn't be visualized by ordinary physical detectors. The exposed grains increase in sensitivity when exposed to a unique chemical solution while processing the image. This process forms black metallic silver, which gets hanged on both sides of the sheet, creating the final image. 

When radiologists select the X-ray sheet of choice to perform imaging, there are some factors to consider. First and most important, the type of used radiation, whether it is X-ray beams or radioactive gamma rays. Then, the second factor is the shape, the location, and composition of the targeted part to be examined. The selection process should preserve a balance between the overall factors.

The medical sheet comes in various packaging options with the most used packaging being individual sheets, in a cartoon box, each sheet enveloped in a holder to protect it from light exposure. They are available in multiple sized options according to the purpose of use and the type of imaging.

Medical film processing

During the processing, the medical film gets exposed to multiple chemical solutions within certain time intervals, in the following steps: 

1- The Exposure (Latent image creation) 

The transparent image becomes produced as a result of the ionization of the emulsion silver halide. This ionization occurs due to the energy of the photo. It follows the ion exchange in the medium when the free Ag ions deposits on the sheet's negatively charged site.

2- The development

A developer solution applied to the sheet reduces the ionized silver halide by donating an electron. Thus precipitate metallic silver forms the final image. This process requires special temperature control to preserve silver precipitation and keeps the unexposed silver halide in its unconverted form.

3- The washing step

This occurs by diluting the chemical agent and washing it away with water, which instantly stops the development process.

4- Fixing

This is done using the fixing bath to remove the unexposed silver halide, leaving the silver metal fixed on the sheet.

5- Drying

The final step is drying the films by hanging them above a tray to catch the excess water while using a fan that is not set directly to the hanging films.

Market Leaders

  1. Agfa-GEVAERT
  2. KIRAN X-RAY
  3. ALLMEDT GmbH & Co. 
  4. CARESTREAM healthcare
  5. FUJIFILM healthcare
  6. VELOPEX International

Conclusion 

The manufacturers of medical film revolutionized radiology in the diagnostic field. The variety in sizes, shapes, base materials, and radiosensitive components resulted in a wide range of options for the radiologists to use in operation. Choosing your radiographic sheet should be based on significant factors, like the nature of the radiation, the physical conditions of the examined part, and the machine used for the scan process. The quality of the radiographic imaging relies on multiple variables; the type and the performance of the X-ray film are considered a major factor in producing a high-quality image. The supplier provides different packaging and delivery materials that fit the workflow and specific intended use. A manual of the appropriate usage and storage will be attached to guide you with handling the materials. It would be best if you preserved the radiographic films away from any light to avoid change in the sheet's radio-sensitivity. You will also need to protect the sheets from scratching and physical strain that could damage the base materials and affect the images' quality.

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