lesson 3 Flashcards
is the most common image receptor used in conventional radiography. It was the first image receptor chosen by Wilhelm Roentgen when he discovered x-rays in 1895. Even with advancements in digital imaging, x-ray film remains widely used due to
high resolution,
affordability,
and reliability.
X-ray film
Manufacturing Process
- Ensures consistency, sensitivity, and durability of the film
- Since x-ray film is light-sensitive, it must be produced and stored in a lightproof environment to prevent accidental exposure.
-Manufactured with vigorous quality control
-Manufactured in total darkness
X-ray films are designed to be sensitive to specific wavelengths of light, usually emitted by intensifying screens.
helps match the film with the proper screen, ensuring optimal image quality and minimal radiation exposure.
Spectral Response
Film Thickness
175 – 300 μm
The thickness of the film influences:
- Thicker films are more durable and less prone to damage.
Handling properties
Thinner films may provide finer details but can be more fragile.
Image resolution
is an essential component of radiographic imaging, providing high-resolution images through a well-controlled manufacturing process.
Its spectral response and physical properties are carefully designed to ensure optimal performance and diagnostic accuracy.
X-ray film
FILM CONSTRUCTION.
Super coat/overcoat/ protective layer
emulsion/ the active layer
adhesive/ substratum coating
base/structural support
is a multi-layered structure designed for high-quality imaging, durability, and efficient processing.
Each layer-supercoat, emulsion, adhesive layer, and base plays a vital role in ensuring that x-ray films produce sharp, detailed, and long-lasting images.
Radiographic film
is the outermost layer of a radiographic film. It is made of a thin, hard gelatin covering that encloses and protects the emulsion layer beneath it.
The supercoat (also called the overcoat or protective layer)
Purpose & Function of supercoat
- Protects the emulsion from damage
- Allows rough handling before exposure
- Prevents physical and chemical damage to the emulsion caused by:
Characteristics of supercoat
Antistatic properties
Extremely strong and durable
Difficult to tear
Thickness of supercoat
2-5 µm (micrometers)
plays a critical role in ensuring the durability and longevity of radiographic films by protecting the delicate emulsion from physical and chemical damage.
This allows for reliable image quality while ensuring that the film withstands handling, storage, and processing conditions.
The supercoat layer
is the core component of radiographic film, responsible for capturing the latent image during exposure to x-rays or light.
This layer’s composition and structure are pivotal in determining the film’s sensitivity, contrast, and resolution
emulsion layer
Composition of emulsion layer
Gelatin
Silver Halide Crystals
Serves as a suspension medium for silver halide crystals, ensuring their even distribution.
is clear, allowing unobstructed passage of light, and porous, permitting processing chemicals to reach the crystals during development. Its flexibility ensures the film can bend without image distortion.
Gelatin:
These are the photosensitive agents within the emulsion. Upon exposure to radiation, they undergo chemical changes, forming the latent image.
Silver Halide Crystals:
The crystals are typically composed of
silver bromide (AgBr) and silver iodide (AgI), with modern emulsions containing approximately 95-98% silver bromide and 2-5% silver iodide.
The size and shape of these crystals influence the film’s speed and image quality.
The emulsion layer’s thickness
it ranges between 5 to 10 micrometers (um).
Types of Emulsion Films
Single Emulsion Film
Double Emulsion Film
• Coating: Emulsion is applied to one side of the film base.
Design: Intended for use with a single intensifying screen.
Identification: Features an identifying notch, typically in the lower left corner, to distinguish the emulsion side.
• Appearance: The emulsion side appears dull, while the non-emulsion side is shiny.
• Applications: Commonly used in duplication, mammography, and fine-detail extremity imaging, where high image detail is paramount.
Single Emulsion Film
Coating: Emulsion layers are applied to both sides of the film base.
Design: Engineered to enhance imaging speed, effectively doubling the sensitivity compared to single emulsion films.
Processing: Remains flat after processing, ensuring ease of handling and consistency.
• Applications: Widely utilized in general radiography, especially for extremity examinations, due to its balanced sensitivity and image quality.
Double Emulsion Film
Composition of Emulsion
- is not merely a passive medium; it plays several critical roles:
Mechanical Support: Holds silver halide crystals uniformly in place, preventing clumping and ensuring consistent image quality.
Chemical Permeability: Its porous nature allows developer and fixer solutions to penetrate and interact with the silver halide crystals during processing.
Optical Clarity: Being transparent, permits light to pass through without distortion, essential for accurate image reproduction, integrity.
Flexibility: Enables the film to withstand bending and handling without compromising the emulsion’s integrity
Gelatin
Size and Shape: Typically around 1 micrometer (um) in size, these crystals can be tabular (flat and triangular), cubic, octahedral, or polyhedral.
The shape and size influence the film’s sensitivity and resolution.
Chemical Composition: Modern radiographic films predominantly use silver bromide, constituting about 95-98% of the crystal composition, with silver iodide making up the remaining 2-5%.
Electrical Properties: Crystals possess a negatively charged surface due to the presence of halide ions (Bromide and Iodide), while the interior is positively charged (Silver).
Silver Halide Crystals
Intentional imperfections, often introduced using silver sulfide, act as sites where latent image formation begins by attracting free silver ions during exposure.
Sensitivity Specks
pivotal in capturing high-quality radiographic images. Understanding its components and their functions provides insight into the film’s behavior during exposure and processing, ultimately influencing diagnostic accuracy.
emulsion layer’s
also known as the substratum or subbing layer, is a vital component of radiographic film, situated between the emulsion and the base. This thin coating serves several essential purposes:
adhesive layer
The adhesive layer maintains a firm bond between the emulsion and the base, ensuring they remain in proper contact during handling and processing.
This bond is crucial for preserving the film’s structural integrity and preventing issues such as separation or peeling of the emulsion from the base
Ensuring Proper Contact and Integrity
By securely attaching the emulsion to the base, the adhesive layer helps prevent the formation of bubbles or other distortions that could occur when the film is bent during handling or processing.
This stability is particularly important when the film is wet and subjected to the heat of development processes.
Preventing Distortions
is indispensable for maintaining the cohesion and functionality of radiographic film, ensuring that the emulsion and base work together seamlessly to produce clear and accurate images.
adhesive layer
serves as its foundational support, providing a stable structure onto which the emulsion layer is coated. Over time, the materials used for the film base have evolved to enhance image quality, safety, and durability.
Base
In the early days of radiography, used as the base material. While they offered excellent dimensional stability, their fragility and weight posed significant challenges.
Glass Plates
Introduced in the 1920s, replaced glass plates.
Despite being lighter and more flexible, it was highly flammable, leading to safety concerns.
Cellulose Nitrate
In the mid-1920s, emerged as a safer alternative to cellulose nitrate.
It retained flexibility and was less flammable but lacked optimal dimensional stability.
Cellulose Triacetate
Since the 1960s, has been the preferred material for radiographic film bases.
It offers superior strength, flexibility, and dimensional stability, ensuring consistent image quality and ease of handling.
Polyester
Thickness: Typically ranges from 150 to 300 micrometers (µm), providing a balance between durability
Dimensional Stability: Maintains consistent size and shape during exposure to processing chemicals and varying temperatures, preventing image distortion.
Transparency and Tint: The base is uniformly transparent and often tinted with a blue dye. This tint reduces eye strain for radiologists, enhancing diagnostic efficiency and accuracy.
Coating: A special light-absorbing dye is applied to the base to prevent crossover effects, which can degrade image quality
Key Characteristics of the Polyester Film Base:
