Lecture Notes: Film and Digital Imaging in Oral Radiology

Introduction

• Primary Methods: Traditional film and digital imaging are the main methods of taking x-rays.

History

• Discovery: Dental x-rays discovered in early 1900s by Kodak.
• Evolution:
  • Film: Requires chemical processing, longer development time.
  • Digital: Introduced in late 1980s, no chemicals needed, near-instant viewing.

Comparison: Film vs Digital

• Film Advantages:
  • Higher quality images and resolution.
• Digital Advantages:
  • Image enhancement (contrast, brightness adjustments).
  • Less radiation needed.

Adoption

• Approximately 50% of dentists use film, the other 50% use digital imaging.

Film X-ray Construction and Process

• Components:
  • Base: Clear, flexible cellulose acetate.
  • Emulsion: Silver halide crystals (silver bromide, iodide, chloride).
  • Single vs Double Emulsion: Double emulsion used in some films.
• Intensifying Screen: Reduces exposure needed, decreases resolution.

Film Speed

• Speed Rule: Faster film needs less exposure.
• Film Speed Ratings: A (slowest) to F (fastest).
• Popular Speeds: D and F.
• Factors Affecting Speed: Crystal size, emulsion layers, radiosensitive dyes.

Image Creation

• Latent Image Formation:
  • X-ray photons convert silver halide to neutral silver atoms.
  • Visible image formed through chemical processing.
• Terms:
  • Radiolucent: Dark areas where photons pass through.
  • Radiopaque: Light areas where photons are blocked.

Chemical Processing

• Steps:
  • Developing: Converts latent image to visible.
  • Fixing: Removes undeveloped silver grains.
  • Washing and Drying.

Digital Imaging

• Categories:
  • PSP (Photo Stimulable Phosphor): Extra step to scan image into computer.
  • CCD/CMOS (Charge Coupled Device/Complementary Metal Oxide Semiconductor): Direct computer connection, instant display.

Comparison

• Contrast Resolution: Film superior to digital.
• Spatial Resolution: Film superior; CCD/CMOS better than PSP.
• Detector Latitude: PSP best, then CCD/CMOS, film last.
• Detector Sensitivity: CCD/CMOS requires less radiation.

Quality Assurance

• Daily Tasks: Record errors.
• Weekly Tasks: Review error log.
• Monthly Tasks: Inspect PSP plates and lead aprons.
• Yearly Tasks: Machine calibration, sensor verification.

Troubleshooting Film Issues

• Underexposure: Inadequate exposure, old chemicals.
• Overexposure: Too much exposure time, overdeveloped.
• Creases/Folds: Cause sharp lines.
• Static Electricity: Black branch-like lines.
• Herringbone Effect: Caused by backward film placement.

Conclusion

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