X-Ray Tubes and Production of X-Rays

Introduction

• X-ray is produced in small tubes called x-ray tubes.
• Used in various medical fields: CT, CBCT, Dentistry, Mammography.
• X-ray tubes have the same function and components across all machines.

Components of X-Ray Tube

• Two main parts:
  • Anode (Positive Terminal):
    • Remember as A+ (positive).
  • Cathode (Negative Terminal):
    • Remember as C- (negative).
• Both parts are housed in an evacuated glass tube to create an air-free vacuum that protects the tube from oxidation.
• This assembly is contained within a tube housing observed in radiology clinics.

Detailed Breakdown of Components

Cathode

• Function: Produces negative electrons.
• Structure:
  • Helical form filament of tungsten (similar to a light bulb filament).
  • High voltage heats the filament, initiating thermionic emission (release of electrons).
  • Creates a cloud of electrons known as "space charge" due to the negative charge.
• Electronic Focusing Cup:
  • Made of molybdenum, serves as a negatively charged concave bowl.
  • Focuses electrons into a narrow beam directed at a small area on the anode (focal spot).

Anode

• Function: Attracts negative electrons and converts energy to X-ray photons.
• Structure:
  • Tank stand target (where electrons are focused).
  • Copper stem for heat dissipation.
• Focal Spot:
  • Area where electrons are concentrated, creating X-rays.
  • Smaller focal spots lead to higher resolution images.

Conclusion

• Understanding x-ray tubes is essential for their application in medical imaging.
• Importance of focusing electrons for image resolution.
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