DXRY311 Roentgenology Prelims

Radiation Physics

• Atoms are the fundamental building blocks of matter, while cells are the basic units of life.
• Atoms consist of three components: electrons (charged negative), protons (charged positive), and neutrons (neutral).
• Electrons occupy specific energy levels or shells around the nucleus and can transition between these shells, producing light as a byproduct.
• Electron displacement between shells is known as excitation, while ionization occurs when an incoming electron dislodges another electron, resulting in radiation.

Atomic Structure

• In a stable atom, the number of protons is balanced by the same number of electrons, making it electrically neutral.
• Protons and neutrons are concentrated in the nucleus, while electrons orbit in predetermined circular or elliptical paths.

Isotopes and Radioisotopes

• Isotopes have the same atomic number (number of protons) but differ in atomic mass due to varying numbers of neutrons.
• Stable isotopes are harmless, while unstable ones are classified as radioisotopes, which emit radiation to achieve stability.
• Radioisotopes are utilized in medical contexts, such as cancer radiation therapy.

Electron Interaction

• High-speed electrons can collide with tungsten atoms in two ways: producing heat (99% of the time) and X-rays (1% of the time).
• Heat is generated when incoming electrons are deflected by outer-shell tungsten electrons, losing energy in the process.

Electron Shells

• Electron shells are designated as K, L, M, N, O, with each shell containing subshells:
  • S shell can hold 2 electrons
  • P shell can hold 6 electrons
  • D shell can hold 10 electrons
  • F shell can hold 14 electrons
  • G shell can hold 18 electrons