Lecture Notes: Oral Radiology Basics

Introduction to Radiation

• Radiation: A form of energy transmitted in waves.
• Examples: Sun radiation, radio waves, x-rays.

Wavelength and Frequency

• Wavelength: Distance between two peaks of a wave.
  • Long wavelength = low frequency (less energy)
  • Short wavelength = high frequency (more energy)
• Frequency: Number of waves passing a point in a certain period.
  • High frequency = more energy
• Velocity: Speed at which waves travel.

X-Ray Physics

• Atom: Basic unit of matter, neutral due to balanced charges.
• Ionization: Process where an atom becomes charged.
• X-ray Production:
  • Cathode (negative) releases electrons.
  • Anode (positive) attracts electrons, releasing radiation.
  • X-ray is produced with only 1% of radiation; remainder is excess.

X-Ray Machine Components

• Control Panel: Regulates exposure factors like milliamperage (mA) and kilovoltage peak (kVp).
• Extension Arm and Tube Head: Directs the x-ray towards the target area.
  • PID (Position Indicating Device): Helps aim x-rays accurately.

Image Quality and Exposure Factors

• mA (Milliamperage):
  • Affects image density.
  • Higher mA = darker image.
• kVp (Kilovoltage Peak):
  • Affects image contrast.
  • Higher kVp = more shades of gray (lower contrast), better for bone abnormalities.
  • Lower kVp = black and white (high contrast), better for detecting cavities.

Radiation Types

• Primary Radiation: Useful for imaging.
• Secondary Radiation: Undesired, often scatter radiation.
  • Compton Scatter: Most common, involves ionization.
  • Coherent Scatter: No ionization, less common.
  • Photoelectric Effect: Involves ionization, no scatter.

Imaging Techniques

• Paralleling Technique: Less distortion, beams perpendicular to film.
• Bisecting Technique: More challenging, requires visualization of imaginary bisecting line.

Radiographic Errors

• Fogged Film: Caused by excess radiation or improper handling.
• Dark Film: Overdevelopment or high temperature.
• Light Film: Underdevelopment or low temperature.
• Clear and Black Radiographs: Exposure issues (e.g., no exposure or exposed to light).

Radiographic Positions and Techniques

• Vertical Angulation: Positive (aim from top), Negative (aim from below).
• Horizontal Angulation: Aimed directly at occlusal plane.

Special Considerations

• Bitewing Radiographs:
  • Used for detecting interproximal cavities or periodontal disease.
  • Vertical bitewings for increased bone level visibility.

Test Question Recaps

• Contrast is affected by kVp.
• Velocity describes wave speed.
• Useful beam is primary radiation.
• Low contrast images show many shades of grey.

Conclusion

• Understanding the basics of x-ray production, radiation types, and imaging techniques is crucial for effective radiographic analysis and safety in oral radiology.