MEDRADSC 2X03 Study Guide - Fall 2018, Comprehensive Midterm Notes - Ionizing Radiation, Mitosis, Macromolecule
12 Oct 2018
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MEDRADSC 2X03
MIDTERM EXAM
STUDY GUIDE
Fall 2018
2X03 MIDTERM NOTES:
Radiobiology → study of action of ionizing radiation on living things
Safety in use of radiation → controlling quantity received, body irradiated, conditions,
minimizing detriment and maximizing benefit to us.
Contributions from man-made radiation sources → fallout from weapon testing, extra cosmic
rays from air travel, dental x-rays, nuclear power plans, luminous wristwatches, buried
radioactie aste, TV’s ad coputer oitors ad edical x-rays [radiography and NucMed &
therapeutic procedures like radiation therapy and radiopharmaceutical therapy & medical
devices like pacemakers and arterial stents]
ALARA principle balances → benefit of use of radiation, likelihood of detriment from radiation
and cost of minimization of exposure.
X-ray interactions with matter:
• Exponential function
• Depends on:
o Mass attenuation coefficient/linear attenuation coefficient
o Density of the material
o Thickness of the material
o Incident x-ray intensity
• For diagnostic xrays (range of 10-150 kEV) →
o Photoelectric effect
▪ Dependent on the x-ray energy and the Z of the material.
find more resources at oneclass.com
find more resources at oneclass.com
▪ Removal of inner shell electron – orbital electrons rearrange them selves
producing either a characteristic or an auger electron.
o , Coherent scatter
▪ No change in energy, uses low energy (less than 10 kev), has a forward
scatter and has little contribution to the image (since photon is so small
with respect to energy when it interacts with the atom it has nothing left)
o Compton scatter.
▪ Uses an outer shell electron, uses high energy, the xray deflects at an
angle with reduced energy (could be 0-80% less) but still free to interact
with others
Radiation therapy ranges from 1.02 meV the predominant types of interactions are:
• Pair production
o Incident photon approaches nucleus then it disappears and the energy is
transformed to produce 2 particles – negative and positive charged electron
• Photodisintegration
o Occurs at 5-10 mev
o Incident photon penetrates nucleus and deposits energy – excess energy in
nucleus results in a particle being ejected.
High energy Neutrons:
• Produced as a by product of x-ray and electron beams in linear accelerators operating at
10 meV
• Experience multiple scatterings within room (walls, floors, ceiling)
• Small fraction reaches room entrance
• Elastic Scattering:
o In tissue, usually proton of hydrogen nucleus set in motion – total EK conserved.
• Inelastic scattering:
o Some transferred energy used in overcoming binding forces (final total EK <
initial EK), nuclear fragments are particulate radiations
Direct Ionizing Radiation:
• Collisional interaction of electrostatic fields causes ionization → high energy charged
particles are directly ionizing.
• Ex. Protons, alpha particles
Indirectly Ionizing Radiation:
• Energy transfer causes released of energetic charged particles (recoil electrons), which
then are directly ionizing → photons and uncharged particles are indirectly ionizing.
• Ex. Gamma rays, x-rays, neutrons
IONIZATIONS → BROKEN CHEMICAL BONDS → CHANGED MOLECULAR STRUCTURE →
CHANGED CHEMICAL BEHAVIOUR
Radiation Interaction in the Cell:
• Effect mainly due to damage to biologic macromolecule → dna/rna/protein which are
considered critical targets
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Radiobiology study of action of ionizing radiation on living things. Safety in use of radiation controlling quantity received, body irradiated, conditions, minimizing detriment and maximizing benefit to us. Alara principle balances benefit of use of radiation, likelihood of detriment from radiation and cost of minimization of exposure. X-ray interactions with matter: exponential function, depends on, mass attenuation coefficient/linear attenuation coefficient, density of the material, thickness of the material. Compton scatter: uses an outer shell electron, uses high energy, the xray deflects at an angle with reduced energy (could be 0-80% less) but still free to interact with others. Radiation therapy ranges from 1. 02 mev the predominant types of interactions are: pair production. Incident photon approaches nucleus then it disappears and the energy is transformed to produce 2 particles negative and positive charged electron: photodisintegration, occurs at 5-10 mev. Incident photon penetrates nucleus and deposits energy excess energy in nucleus results in a particle being ejected.
