Production And Use Of X-Rays (Copy)

Production of X-rays by Electron Bombardment

• X-rays are produced when high-speed electrons strike a metal target (usually tungsten) inside an evacuated X-ray tube.
• Electrons are emitted from a heated filament (cathode) via thermionic emission and are accelerated toward the anode (metal target) by a high potential difference.
• When these electrons decelerate rapidly at the metal target:
  • Their kinetic energy is converted into X-rays and heat.
  • X-rays are emitted via bremsstrahlung (braking radiation) and characteristic X-rays.
• Minimum wavelength (λₘᵢₙ) of X-rays:
  • When all the kinetic energy (eV) of the electron is converted into a single X-ray photon:
    E = eV = hc / λₘᵢₙ
    ∴ λₘᵢₙ = hc / eV
    where:
    • h = Planck’s constant (6.63 × 10⁻³⁴ J·s)
    • c = speed of light (3.00 × 10⁸ m/s)
    • e = elementary charge (1.60 × 10⁻¹⁹ C)
    • V = accelerating potential (volts)

Use of X-rays in Medical Imaging

• X-ray imaging is widely used to visualize internal body structures, especially bones and dense tissues.
• Different tissues absorb X-rays to different extents depending on their density and composition:
  • Bone absorbs more X-rays → appears white.
  • Soft tissues absorb less → appear darker.
• Contrast in X-ray Imaging:
  • Defined as the difference in X-ray absorption between adjacent tissues or structures.
  • Contrast agents like barium sulfate or iodine compounds are sometimes used to enhance image visibility of soft tissues or blood vessels.

Attenuation of X-rays in Matter

• As X-rays pass through matter, they lose intensity due to absorption and scattering.
• The attenuation is exponential, described by the equation:
  I = I₀e⁻ᵘˣ
  where:
  • I = transmitted intensity
  • I₀ = initial intensity
  • μ = attenuation coefficient (depends on material)
  • x = thickness of the material
• This equation allows for calculation of how much X-ray intensity is reduced after passing through tissue of thickness x.

Computed Tomography (CT) Scanning

• A CT scan uses multiple X-ray beams taken at different angles around a patient.
• These images are used to reconstruct a 2D cross-sectional image (slice) of the body using a computer.
• By scanning multiple slices along the body’s axis and combining the data, a 3D image of the internal structure is created.
• CT scans provide:
  • Greater detail and contrast than standard X-ray imaging.
  • Clearer images of soft tissues, tumors, organs, and blood vessels.

Key Differences: Standard X-rays vs CT Scan

Written and Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change A2 Level Physics Full Scale Course