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88 Cards in this Set
- Front
- Back
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What's the value of electron charge?
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1.6E-19 Columbs
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What's the definition of mass number?
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What quantity counts the number of nucleons in an atom?
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What's the symbol for atomic mass number?
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"A" is the atomic symbol for?
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What's the definition of atomic number?
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What quantity counts the number of protons in an atom?
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What do isotopes have in common?
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What are a pair of atoms with equal number of protons but different number of neutrons called?
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What do isotones have in common?
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What are a pair of atoms with equal number of neutrons but different number of protons called?
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What do isobars have in common?
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What are a pair of atoms with equal number of nucleons but different numbers of neutrons and protons called?
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What do isomers have in common?
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What are a pair of atoms with the same number of protons and neutrons but different energy states called?
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What factor indicates a nuclide is more likely to be stable?
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A nuclide with an even number of protons and an even number of neutrons
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1 amu in kg is
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What has a mass of 1.66E-27 Kg
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What is the half-life of 226Ra?
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Which nuclide has a half-life of 1600 years?
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What is the half-life of 222Rn?
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Which nuclide has a half-life of 3.83 days?
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What is the half-life of 60Co?
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Which nuclide has a half-life of 5.26 years?
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What is the half-life of 137Cs?
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Which nuclide has a half-life of 30.0 years?
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What is the half-life of 192Ir?
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Which nuclide has a half-life of 73.8 days?
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What is the half-life of 198Au?
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Which nuclide has a half-life of 2.7 days?
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What is the half-life of 125I?
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Which nuclide has a half-life of 59.4 days?
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What is the half-life of 103Pd?
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Which nuclide has a half-life of 17.0 days?
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What is the half-life of 106Ru?
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Which nuclide has a half-life of 1.02 years?
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What is the emission of 226Ra?
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Which nuclide has an average gamma-emission energy of 0.83 MeV?
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What are the emission of 60Co?
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Which nuclide has gamma-emission energies of 1.17 and 1.33 MeV?
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What is the emission of 137Cs?
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Which nuclide emits a gamma ray of energy of 0.662 MeV?
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What is the emission of 192Ir?
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Which nuclide has an average gamma-emission energy of 0.38 MeV?
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What is the emission of 198Au?
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Which nuclide emits a gamma ray of energy of 0.412 MeV?
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What is the emission of 125I?
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Which nuclide emits a gamma ray of energy of 28 KeV?
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What is the emission of 103Pd?
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Which nuclide emits a gamma ray of energy of 21 KeV?
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What is the emission of 106Ru?
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Which nuclide emits a beta-particle of energy of 3.54 MeV?
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International Commission on Radiological Protection (ICRP)
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• One of the first standard setting bodies
• Reports form basis for national protection guildelines |
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National Council on Radiation Protection and Measurements (NCRP)
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Primary standard-setting agency in the United States
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Nuclear Regulatory Commission (NRC)
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Regulatory powers over the use of reactor-produced materials.
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State Regulatory Bodies
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Regulates naturally occurring radioactive materials.
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Four Radiation Protection Bodies
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• International Commission on Radiological Protection (ICRP)
• National Council on Radiation Protection and Measurements (NCRP) • Nuclear Regulatory Commission (NRC) • State Regulatory Bodies |
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Dose equivalent
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H = D·Q, D: Absorbed dose, Q: Quality factor. [H] = Sievert = Joule/Kg
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Quality Factor
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Conservative measure of damage cause by each type of radiation per unit absorbed dose.
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Quality factor for X-rays
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1
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Quality factor for γ-rays
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1
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Quality factor for electrons
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1
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Quality factor for thermal neutrons
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5
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Quality factor for neutrons
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20
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Quality factor for heavy particles
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20
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Quality factor for protons
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5
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Effective dose equivalent
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HE = ΣWTHT W: tissue weighting factor, H: tissue dose equivalent
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Weighting factor
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Proportionate risk from each tissue when body is irradiated uniformly.
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Risk coefficient
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Risk of damage to specific site per unit dose equivalent.
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Total risk coefficient
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165E-4/Sv, 125 is somatic risk, 40 is genetic risk. 1xE-6 is used for radiation protection calculations.
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Sources of background radiation
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• Cosmic: varies with elevation, HE ≈ 0.27 mSv/y
• Terrestrial: varies with location, HE ≈ 0.28 mSv/y • Inhaled: depends on building material, HE ≈ 2.0 mSv/y • Internal: mainly from potassium-40, HE ≈ 0.40 mSv/y • Total HE ≈ 3.0 mSv/y |
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Stochastic effect
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Probability increases with absorbed dose but serverity does not.
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Nonstochastic effect
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Increases in severity with increase absorbed dose, as more tissue is damaged.
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Assumed dose-risk relationship for radiation protect
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Linear, non-threshold
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Dose equivalent limit for radiation workers
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50 mSv/year
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Dose equivalent limit for general public
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5 mSv/year
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Dose equivalent limit for declared pregnant worker
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5 mSv/year, 0.5 mSv/month
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Dose equivalent limit for non-controlled areas
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0.01 mSv/week
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Dose equivalent limit for controlled areas
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0.1 mSv/week
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Barrier thickness calculation
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1. Workload W: Weekly dose delivered at 1m.
2. Use Factor U: Fraction of operating time barrier is exposed. 3. Occupancy Factor T: Fraction of operating time area is occupied. 4. Distance d Barrier Attenuation = P·d·d / WUT |
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Dose equivalent of cosmic background radiation
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Varies with elevation, HE ≈ 0.27 mSv/y
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Dose equivalent of terrestrial radiation
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Varies with location, HE ≈ 0.28 mSv/y
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Dose equivalent of inhaled radiation
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Depends on building material, HE ≈ 2.0 mSv/y
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Dose equivalent internal radiation
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Mmainly from potassium-40, HE ≈ 0.40 mSv/y
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Total dose equivalent from background radiation
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HE ≈ 3.0 mSv/y
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Energy of most Linacs prior to 1950
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300 kVp
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Grenz-ray Therapy
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Therapy using very low eneries, ~20kV or less. No longer used.
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Superficial Therapy
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Treatment using x-rays between 40 to 150 kV
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Othovoltage Therapy
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Treatment using x-rays between 150 and 300 kV. SSD is typically 50cm.
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Megavoltage Therapy
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X-ray, or gamma ray, beams with energy greater than 1 MV.
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Van de Graaff generator (Definition)
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Electrostatic charged particle accelerator capable of producing 2 to 10 MV x-rays. Obseleted by Cobalt machines and Linacs
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Van de Graaff generator (Operation)
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Electrons are spray onto a moving belt of insulating material. They are moved to a collector attached to a dome, producing a high potiential between it and ground. Electrons are released from a filament and accelerated through a series of metal rings to strike a target.
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"Major linac components
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• Power Supply
• Modulator • Electron Gun • Magnetron or Klystron • Accelerator Tube • Wave Guide System • Treatment Head |
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Purpose of linac modulator |
Uses direct current from the power supply to create a pulse-forming network: flat-topped DC pulse a few microseconds in duration.
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Purpose of linac magnetron or klystron
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Take pulse DC from the modulator and produces microwave pulses to the wave guide system
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Magnetron output
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Microwave pulses with frequency of about 3000 MHz, a few milliseconds duration, and several hundred per second.
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Magnetron physical description
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Cylindrical copper housing with central cathode and eight outer resonant cavities
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Magnetron principle of operation
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Cathode is heated via a filament, generating electrons by thermionic emission. A static, axial magnetic field is applied, and an DC electric field pulsed between cathode and anode. Electrons released from the cathode move in complex spirals towards resonant cavities, radiating microwaves.
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Krystron output
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Amplified microwaves
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Krystron physical description
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Cylindrical chamber separating two cavities with a hot wire filament as a cathode.
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Krystron principle of operation
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Low level microwaves traversing the first cavity cause velocity modulation in electrons emerging from the cathode, creating electron bunches. When these reach the second cavity, the charge they induce at the end of the tube causes deceleration, producting high-power microwaves.
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Purpose of scattering foil
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Spread electron beam
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How do Dmax and PDD vary with increasing beam energy?
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Dmax gets deeper, i.e. increases.
PDD decreases in the build-up region and increases after Dmax |
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What is the formula to calculate electron density from mass density?
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ρe = ρm•NA•(Z/A)
ρe : electron density ρm: mass density NA: Avogadro’s number Z: Atomic number A: Atomic weight |
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How does PDD vary with increasing field size?
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PDD increases with increasing field size due to increased scatter
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How does PDD vary with increasing SSD?
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PDD increases with increasing SSD. The dose rate decreases, but the dose relative to the reference point increases. i.e. the dose a dmax will be smaller, but so will the difference between the dose at dmax and that at other points on the CAX.
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How can PDD be corrected for a different SSD?
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Using the Mayneord Factor:
P(d,r,f2) = P(d,r,f1) · (f1+dm)^2/(f1+dm)^2 · (f1+d)^2/(f2+d)^2 |
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How is TAR defined?
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Tissue-air ratio (TAR) is the ratio of dose at a given point (Dd) in a phatom to the dose at the same point in free space. It is considered independent of source distance, depending only on depth and field size.
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How does TAR vary with increasing depth?
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Much like a PPD curve, TAR increases to a peak at dmax then follows an exponential decay.
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What is Backscatter Factor?
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Backscatter factor is the TAR @ dmax, or Dmax/D(free space).
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What is the equation relating PPD to TAR?
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P(d,r,f) = TAR(d,rd)·1/BSF(r)·(f+dm)^2/(f+d)^2
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What is SAR?
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The Scatter-Air Ratio is the ratio between scattered dose at a point in a phaton to the dose in free space at that point.
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What is the equation relating SAR to TAR?
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SAR(d, rd) = TAR(d, rd) – TAR(d,0)
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