Radiology Physics - Introduction Quiz

Introduction to Radiology Physics

• Course title: Radiology Physics & Instruments (RMI216)
• Lecture title: Introduction to Radiology Physics (LEC.1)
• Instructor: Dr. Mohammed Sayed Mohammed
• Affiliations: National Cancer Institute, Cairo University, Faculty of Applied Health Sciences, Galala University, Qualified Expert of Radiologic Sciences, Ministry of Health, Egypt; Former Supervisor of Diagnostic Radiology Department, College of Applied Medical Sciences, University of Hail, KSA; Former STEM Ambassador, University of Reading, UK.

Atomic Structure, X-rays Production, and Radioactivity

• Atoms consist of three main particles: protons (+ charge), neutrons (+/- charge), and electrons (- charge).
• Protons and neutrons are located in the nucleus.
• Electrons orbit the nucleus.
• In radiology, electron interactions with radiation create medical images.
• Atomic behavior is crucial for understanding X-ray production.

Energy Levels & Ionization

• Electrons exist in distinct energy levels.
• Ionization occurs when electrons gain enough energy to leave an atom.
• This process is relevant in X-ray production.
• Fundamental physical constants, such as Avogadro’s number (NA), Speed of light (c), Electron charge (e), Electron/positron rest mass (me), Proton rest mass (mp), and Neutron rest mass (mn) are important for calculations.

Basic Quantities and Several Derived Physical Quantities and Units in SI Units

• Physical quantities and their SI units, as well as their practical units commonly used in radiation physics and conversion factors are provided. (units for Length, Mass, Time, Current, Temperature, Mass density, Current density, Velocity, Acceleration, Frequency, Electric charge, Force, Pressure, Momentum, Energy, Power are explicitly presented in the slides)

Classification of Ionizing Radiation

• Ionizing radiation carries sufficient energy to remove electrons from atoms.
• It can be categorized into: Directly ionizing (radiation directly interacts with matter) and Indirectly ionizing (radiation interacts with matter in a stepwise manner).
• Both types are relevant in medicine.

Classification of Indirectly Ionizing Photon Radiation

• Includes: UV light (limited medical use), X-rays (produced by accelerated electrons: used in imaging and treatment), and Gamma rays (produced by nuclear transitions/decays: used in imaging and treatment).
• X-rays and Gamma-rays differ based on their origin.
• Photons come from different sources.

Characteristic X-rays

• Orbital electrons occupy the lowest energy state.
• Displaced outer shell electrons transition to fill vacancies.
• This transition releases characteristic energy that forms photons.

Bremsstrahlung

• Light charged particles (like electrons) slow down due to interactions with other charged particles (like atomic nuclei).
• Kinetic energy is converted to electromagnetic radiation, forming X-rays with a continuous spectrum.

Gamma Rays

• Nuclear reactions or spontaneous nuclear decays can leave the nucleus in an excited state.
• The nucleus transitions to a more stable state by emitting a gamma ray.
• Gamma rays carry characteristic photon energy.

Annihilation Quanta

• Positrons result from beta+ nuclear decay or high-energy photon interactions.
• Positron energy loss occurs via Coulomb interactions (with orbital electrons and atomic nuclei).
• Positron annihilation occurs when positrons collide with orbital electrons, converting both particles into two gamma-rays.

Radiation Quantities and Units

• Exposure (X): Ability of photons to ionize air.
• Kerma (K): Energy transferred to charged particles per unit mass of absorber.
• Dose: Energy absorbed per unit mass of medium.
• Equivalent dose (H): Dose multiplied by radiation weighting factor.
• Effective dose (E): Equivalent dose multiplied by tissue weighting factor.
• Activity (A): Number of nuclear decays per unit time.

Basic Definitions for Atomic Structure

• Constituent particles: Proton, Neutron, Electron
• Nucleons: Proton and Neutron
• Atomic number (Z): Number of protons.
• Atomic mass number (A): Number of nucleons (protons + neutrons).
• Atomic mass (ma): Mass of an atomic particle or molecule.

Basic Definitions for Nuclear Structure

• Nuclear physics conventions for designating a nucleus (X).
• Classifications of isotopes, isobars, & isotones
• Nuclear binding energy per nucleon.

How X-Rays Are Produced

• X-rays are created when high-energy electrons hit a metal target in an X-ray tube.
• Two types of X-rays are produced: Bremsstrahlung and Characteristic radiation.

Properties of X-rays

• X-rays are invisible.
• Penetrate soft tissue; absorbed by bones.
• Produce diagnostic images.

Types of Radiation

• Alpha, Beta, and Gamma radiation have different penetrating abilities and applications.
• Alpha particles are easily blocked by paper.
• Beta particles can penetrate skin but are stopped by materials like plastic.
• Gamma rays have high penetration power and are used in diagnostics and therapies.

Conclusion

• Atomic structure, energy levels, X-ray production, and radioactive decay are key principles in radiology.
• X-rays are produced through ionization.
• Understanding these concepts is crucial for advanced imaging techniques.

Test your knowledge on the fundamentals of radiology physics, including atomic structure, X-ray production, and the principles of ionization. This quiz is aimed at students of the Radiology Physics & Instruments course. Enhance your understanding of how these concepts apply in medical imaging.