DEN 130 1 H - Dental Radiology- 39

Digital Imaging, Dental Film, and Processing Radiographs Study Notes

Chapter 39

Learning Objectives: Digital Radiography and X-Ray Film Processing

  • Pronunciation, definition, and spelling: Familiarize with key terminology related to digital radiography and film processing.

  • Purposes and uses of digital radiography: Understand the applications in dental practices.

Fundamental Systems of Digital Radiography

Equipment Necessary for Digital Radiography

  • Digital radiography requires specific equipment not used in traditional film-based systems.

Types of Dental Image Receptors

  • Direct Imaging: Involves sensors that convert x-ray photons directly into digital signals.

  • Indirect Imaging: Utilizes phosphor plates, coated to capture x-ray images, which then require scanning.

Scanning and Clearing Phosphor Plates

  • Phosphor plates must be scanned to digitize the images, followed by a clearing process to prepare the plates for reuse.

Digitizing Radiographs Using a Scanner

  • The process involves converting analog images into digital format using scanning technology.

Advantages and Disadvantages of Digital Radiography

  • Advantages: Reduced exposure time, immediate image availability, easier sharing.

  • Disadvantages: Higher initial cost, potential for technological issues.

Changes Made by Digital Imaging Software

  • Digital imaging software allows for manipulation of images: contrast, brightness, sharpness, and more.

X-Ray Film and Film Processing

Terminology of Conventional Film-Based Techniques

  • Understanding basic terminology is essential when discussing film out of context.

Common Types of Beam Alignment Devices

  • Devices like Rinn XCP instruments assist in proper alignment and positioning of the beam for accurate imaging.

Introduction to Digital Radiography

  • Digital radiography has been prevalent since 1987 and is increasingly adopted in North America.

  • Digital images (electronic signals) are displayed almost instantly on computer monitors, differing from traditional radiographs.

  • These images can easily be emailed or printed on high-quality paper.

Conventional X-Ray Machines

  • Even with digital systems, traditional x-ray machines are used for exposure.

  • Strict infection control is necessary due to the reuse of sensors and phosphor plates.

Types of Digital Imaging Systems

Methods of Acquiring Digital X-Ray Images

  • Two main methods include direct imaging and indirect imaging.

Direct Digital Imaging

  • Image Receptor: A solid-state sensor containing an x-ray sensitive silicon chip.

  • Common Sensor Type: Charge-coupled Device (CCD) sensors, which may be either wired or wireless.

Indirect Digital Imaging

  • Image Receptor: A flexible plate coated with phosphor crystals, which stores x-ray energy.

  • Scanning Process: A scanner uses a laser to convert the stored energy into digital images.

Phosphor Storage Imaging Summary

  • Recharging Plates: After scanning, plates are exposed to bright light to clear residual energy.

  • Infection Control Measures: Plates must be housed in protective barrier envelopes.

Digitizing Images from Film

  • Film-based radiographs can be digitized for computer display.

  • This conversion captures image details similar to placing film on a duplicator lightbox, albeit with slight detail loss.

Digital Imaging Software Programs

  • Capabilities include performing electronic enhancements on images.

  • Variables that can be altered include:   - Contrast   - Brightness   - Image size   - Sharpness   - Inversion (black/white reversal)   - Pseudocolor alteration

X-Ray Film and Film Processing Techniques

Traditional vs. Digital Techniques

  • Many practices still rely on conventional techniques. Understanding traditional processing is critical for quality diagnostics.

Key Definitions

  • Film: Before processing, termed 'film'. Once developed, termed 'image' or 'radiograph'.

Positioning Instruments for Radiography

Definition and Purpose

  • Instruments used to position x-ray films or digital sensors, minimizing radiation exposure to patient fingers.

Types of Intraoral Positioning Instruments

  • Similar structure for digital receptors and conventional film holders, differing primarily in size.

Beam Alignment Devices

  • Important for aligning beam during x-ray procedures to ensure accurate imaging.

  • Examples include color-coded plastic components to aid in proper PID positioning.

Dental Film Composition and Processing

Film Composition

  • Made of a cellulose acetate base, coated with sensitive silver halide emulsions.

Latent Image Formation

  • Interaction of radiation with silver halide crystals creates a latent image, which is invisible until processed.

Film Speed

  • Definition: Amount of radiation needed to achieve standard density in a radiograph.

  • Factors influencing film speed include wireness and sensitivity of halide crystals.

  • F-speed film is the latest in development, reducing patient exposure by up to 60% compared to older film types.

Types of Film in Radiography

Categories

  1. Intraoral Film

  2. Extraoral Film

  3. Duplicating Film

Intraoral Film

  • Packaged in protective film packets to shield from light.

  • Contains emulsion on both sides to require less radiation.

Extraoral Film Definition and Examples

  • Used outside the mouth; includes panoramic and cephalometric films.

Film Cassette Description

  • A casing that holds the extraoral film, must not let light in.

Intensifying Screen Mechanism

  • Enhances the effect of radiation, reducing exposure time but slightly decreasing image detail.

Duplicating Film

  • Used only in darkroom settings, does not engage with x-rays directly.

  • The longer exposure to light results in a lighter image, contrasting with regular x-ray films.

Film Storage Guidelines

  • Store according to manufacturer specifications to prevent age-related degradation (age fog).

Film Processing Steps and Techniques

Importance of Proper Processing

  • Key to achieving diagnostic-quality radiographs.

  • Poor processing can result in unnecessary patient radiation exposure through re-examination.

Five Steps in Film Processing

  1. Development

  2. Rinsing

  3. Fixation

  4. Washing

  5. Drying

Development Process

  • Involves a developer solution that reduces exposed silver halide crystals into black metallic silver, softening the emulsion.

Rinsing Process

  • Essential for removing developer and stopping the development process.

Fixing Process

  • Removes unexposed crystals and hardens the film emulsion.

  • Permanent fixation ensures that visible images remain intact without fading.

Washing Process

  • Important to eliminate all chemicals, requiring approximately 20 minutes.

Drying Process

  • Films must be completely air-dried or heated before handling.

Processing Solutions and Maintenance

  • Available as powder, ready-to-use liquids, or liquid concentrates; regular checks and replenishment are vital.

Darkroom Requirements for Processing

Essential Elements

  • Light-tight environment to prevent film fog.

  • Cleanliness and infection control are paramount.

  • Proper equipment for processing solutions and film handling.

  • Safe lighting practices must be adhered to, including using safelighting for film development.

Common Processing Errors

Types of Errors to Recognize

  • Time, temperature, chemical contamination, film handling, and lighting-related errors.

Common Manifestations

  • A range of adverse outcomes includes overdevelopment, fogging, or underexposure.