Nuc Med Exam 2

what is a charged particle

particle with an electrical charge (alpha and beta particles, protons, charged nuclei, and electrons),

interacts with coulomb force that surrounds it and another particles.

Three types of interactions for charged particles

Ionization, excitation, bremsstrahlung radiation

Alpha particle (Characteristics)

• charged particle

• short and straight track

• slow velocity

Beta particle (Characteristics)

• charged particle

• long and tortuous track

• same size as electrons

Bremsstrahlung interaction

Charged particle interacts with nucleus’ electrical field, losing KE and emitting a photon

Ionization interaction

charged particle interacts with electric field of orbital electron, causing orbital electron to separate from atom as another charged particle

Excitation interaction

charged particle interacts with orbital electron but not enough energy to eject it, instead the orbital electron moves up an orbital, then going back down to the vacant spot, releasing a char. Xray or Auger electron.

delta rays

secondary electrons, that are charged and go on to produce other interactions.

Shielding for Gamma rays/Photons

lead or tungsten

Shielding for Alpha particles

lead or tungsten, cannot interact via Brem. and always have associated gamma ray

Shielding for Positrons

lead or tungsten because of annihilation process

Shielding for Beta minus

Shield with low-Z then lead

Charge particle factors: mass goes up

range goes down

Charge particle factors: charge goes up

range goes down

Charge particle factors: energy goes up

range goes up

Charge particle factors: density goes up

range goes down

Types of photon interactions

• Photoelectric effect

• compton effect

• pair production

Photons & neutrons

travel unimpeded for long distances, not effected by coulomb force, they interact by colliding with atoms

photoelectric effect

photon interacts/hits an inner-shell orbital electron,

• electron absorbs the photon and ejects iteself turning into a charged particle.

Compton Effect

photon interacts/hits an outer-shell electron, ejecting the electron and photon deflecting into a different direction.

Pair production

high-energy photon hits the nucleus of an atom, transfers all of it’s energy to produce/emit an electron and positron (beta plus). Which go on as charged particles, positron goes to do annihilation process.

penetrating radiation

neutrons and gamma rays (penetrating or non-penetrating)

non-penetrating radiation

alpha and beta particles (penetrating or non-penetrating)

Neutron interactions (Characteristics)

• massive size

• no electrical charge

• lose significant kinetic energy when colliding with nucleus.

Coulomb force

the force field created by an object with electrical
charge, and affecting any other object with
electrical charge

covalent bond

electrons orbitals of two atoms interact forming a bonding orbital

Roentgren

the amount of radiation to produce 2 billion ionizations in a cubic cm of air

Attinuation

removal of gamma ray from photon beam as it goes through matter and interacts.

Transformation

gamma ray that passes through the material

Linear attenuation coefficient

the fraction of attenuated photons in a beam per unit thickness of a material.

half-value layer

thickness of material to attenuate 50% of gamma ray beam