Lecture Review: Nuclear Physics and Imaging Techniques

Introduction to Nuclear Physics and Radioactivity

Nuclear Physics Overview

  • Nuclear Physics: The study of the atomic nucleus structure and its interactions, involving processes such as radioactive decay, nuclear fission, and fusion.
  • Radioactivity: A nuclear process where unstable nuclei release energy in the form of radiation to attain stability, following the law of conservation of charge.
  • Stability: Determined by the neutron-to-proton ratio.
  • Units of Radioactivity:
    • Curie (Ci)
    • Becquerel (Bq)
    • Roentgen
    • Sievert (Sv)

Sources of Radiation

Natural Sources

  • Terrestrial Radiation: From minerals and materials in the earth.
  • Cosmic Radiation: Higher exposure at higher altitudes and during air travel.
  • Internal Radiation: From naturally occurring isotopes within the body, e.g. potassium-40 in bananas.

Man-Made Sources

  • Nuclear Power Plants: Utilize fission reactions for electricity generation.
  • Atmospheric Testing: Fallout from nuclear weapons testing, e.g., Hiroshima and Nagasaki.

Types of Radiation

Ionizing Radiation

  • Can produce ions upon interacting with matter and may be harmful (e.g., X-rays, gamma rays).
  • Common types include:
    • Alpha Particles: Consist of 2 protons and 2 neutrons, causing significant changes in the originating atom upon decay.
    • Beta Particles: May be electrons or positrons emitted during decay.
    • Gamma Radiation: A high-energy photon emitted from an unstable nucleus.
    • Neutron Radiation: A free neutron emitted during fission, inducing ionization indirectly.

Non-Ionizing Radiation

  • Includes electromagnetic radiation (e.g., radio waves, visible light) that cannot produce ions directly.

Interaction with Matter

  • Radiation cannot be sensed directly but interacts with atoms, leading to two effects:
    • Excitation: Raising orbital electrons to higher energy states.
    • Ionization: Removal of electrons to create ion pairs.

Biological Effects of Radiation

  • Varies significantly among individuals.

Acute Exposure Effects

  • Damage to DNA yields risks of cancer, genetic defects, and potentially death.
  • Direct action (interaction of radiation with DNA) vs. indirect action (free radical formation).

Radiation Damage to DNA

  • Types of Damage:
    • Single-Strand Breaks: Often caused by hydroxyl radicals.
    • Double-Strand Breaks: More severe, can involve close proximity breaks within DNA.
    • Base Changes and Loss: Can cause mispairing or loss of genetic information, impacting cellular function and leading to mutations.

Radiation Detection and Measurement

  • Radiation detection is essential as it cannot be perceived by senses.

Types of Detectors

  • Gas-Filled Detectors: Ionize gas to produce charge resulting in an electric signal.
  • Scintillation Counters: Convert radiation energy to light signals measurable by photomultipliers.

Radioisotopes and Their Uses

  • Isotopes are variations of elements with the same number of protons but different neutrons.
  • Clinical Applications:
    • Monitoring organ functions.
    • Tracing drug paths in medical diagnostics.
    • Radioactive iodine in thyroid treatments.

Introduction to Microscopic Techniques

  • Microscopy: Techniques used to observe objects not visible to the naked eye.
    • Types of Microscopes: Optical, electron, and scanning probe.

Spectroscopic Techniques

  • Spectroscopy: Interaction study between matter and electromagnetic radiation, providing analytical insights.

Applications

  • UV-Visible Spectroscopy: Absorption measurements to identify substances.
  • Mass Spectrometry: Ionization and mass-to-charge ratio analysis.

Imaging Techniques

  • Used to visualize internal structures of organisms, developed after X-ray discovery.
  • X-ray Radiography: Producing images of the body using differential absorption of X-rays.
  • MRI: Non-invasive imaging using magnetic fields and radio waves.

Introduction to Biophysical Chemistry

  • An interdisciplinary field that combines biology, chemistry, and physics.
  • Utilizes techniques like chromatography and spectroscopy to study biological molecules.