UNIT 2B RADIATION BIOLOGY (IONIZING RADIATION)

IONIZING RADIATION

refers to high-energy radiation that can eject tightly bound electrons from atoms, creating ions

• High Energy

• Ability to ionize atom

• Short Wavelength or High Frequency

• Penetrating Power

• Biological Damage

Characteristics of Ionizing Radiation

α

• Consist of two protons and two neutrons.

• Relatively large and heavy.

• High ionization potential but low penetration.

• Stopped by paper, clothing, or even human skin

α

• The nucleus emits an alpha particle (Helium nuclei), which is made up of two protons and two neutrons

• This results in the atom becoming a different element with two fewer protons and two fewer neutrons.

β

• High-energy, high-speed electrons (β-) or positrons (β+).

• Moderate penetration.

• Can be stopped by plastic, glass, or a few millimeters of aluminum.

  • Positron

  • Negatron

β+ Decay

• Proton rich - Neutron poor

• Positron Emission

• Emission of positron with simultaneous conversion of one proton into a neutron

• Proton converted into a neutron (Z-1)(n+1)

• Is accompanied by emission of a neutrino

• Used in PET imaging

β- Decay

• Neutron rich - Proton poor

• Creation/Emission of an electron from the nucleus

• Emission of electron with simultaneous conversion of one neutron into a proton

• Neutrons is converted into proton (n-1)(Z+1)

• Is accompanied by emission of an antineutrino

Beta Decay

radioactive day that either releases an electron or positron

Neutrino (ν)

• extremely lightweight, electrically neutral particles.

• typically produced in various natural processes, such as nuclear reactions in the sun and supernovae, as well as in man-made processes, including nuclear reactors and particle accelerators

• interact very weakly with matter, making them challenging to detect. They can pass through vast amounts of material without being absorbed or deflected.

Antineutrino (̅ν)

• the antimatter counterparts of neutrinos

• electrically neutral and very lightweight

• produced in various particle interactions, including certain types of nuclear decay processes, such as beta decay

• interact very weakly with matter, making their detection challenging

γ

• Electromagnetic radiation (high-energy photons).

• High penetration ability.

• Requires dense materials (e.g., lead or several centimeters of concrete) to stop

X

• Electromagnetic radiation similar to gamma rays but usually of lower energy.

• Used extensively in medical imaging and industry.

• Requires lead or dense materials for shielding

n

• Particles found in the nucleus of atoms.

• Can cause neutron activation of materials.

• They collide with atoms and make those atoms unstable or even break them apart.

• Used in generating powers in nuclear reactors