Oral radiology lecture 1

Speed of Light

• Speed of light (c) is approximately 299,792 kilometers per second (or 186,282 miles per second).

X-Ray Photon Energy

• As the wavelength of x-ray photons decreases, their energy increases.
• Higher frequency corresponds to higher energy in x-ray photons.

Generation of X-Rays

• X-rays are generated in an x-ray tube when high-speed electrons collide with a target material.
• Essential requirements for x-ray generation include a vacuum environment, a filament to produce electrons, and a target for electron collision.

Maximizing X-Ray Production

• To maximize x-ray production, a high atomic number target material is necessary, such as tungsten.
• Sufficient potential difference in the tube and proper electron focus are crucial.

Focusing Cup and Anode Target Function

• The focusing cup directs electrons toward the target, increasing x-ray output efficiency.
• The target of the anode converts kinetic energy from electrons into x-rays through interactions with the target material.

Focal Spot Size

• As the focal spot size decreases, spatial resolution improves, allowing for clearer imaging.

Material and Design of the Cathode

• The filament in the cathode is typically made from tungsten due to its high melting point and durability.
• A rotating anode design is superior for heat dissipation in an x-ray tube, preventing damage from prolonged exposure.

Function of Components in the X-Ray Tube

• The filament in the cathode heats up to produce electrons through thermionic emission.
• The step-down transformer reduces voltage to heat the filament effectively.
• An autotransformer in the power supply adjusts the voltage to necessary levels for optimal x-ray production.

Controls in X-Ray Machines

• The mA switch controls the quantity of x-rays produced by adjusting the filament current.
• The timer regulates the duration of x-ray exposure; it is often calibrated in impulses.

Bremsstrahlung and Characteristic Radiation

• Bremsstrahlung radiation is primarily caused by high-speed electrons being deflected by atomic nuclei, producing x-rays with a continuous spectrum of energy.
• The majority of x-rays generated in dental units arise from bremsstrahlung radiation.
• Characteristic radiation occurs when electrons eject inner-shell electrons from target atoms, leading to the emission of x-rays with specific energies.

Key Characteristics

• Characteristic radiation has distinct energy levels and is generated when outer-shell electrons fill inner-shell vacancies.
• Bremsstrahlung radiation provides a continuous energy spectrum due to variable energy interactions.