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86 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Dose Equivalent (units)
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Rem, Sievert
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Exposure (units)
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Roentgen
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Absorbed Dose (units)
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Gray, Rad
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Activity (units)
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Becquerel, Curie
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Exposure (definition & unit):
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“The charge liberated by photons in a given mass of air”. (Unit=Roentgen)
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Absorbed dose (definition & unit):
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“The amount of Energy in joules/kg transferred from a photon beam to a medium”. (Unit=Gy).
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Dose Equivalent (definition & unit):
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“The absorbed dose x Quality Factor. (Unit=Sv).
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Dose Equiv>Absorbed Dose for:
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Neutrons.
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(It’s 5 to 20 times as great, depending on neutron Energy – because of higher LET & greater potential for biological damage per Gy.
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Dose Equiv is SAME as Absorbed dose for:
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X-rays, gamma-rays & electrons.
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100µSv = ? Mrem
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10 mrem
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(1Sv=100rem. Thus 100µSv = 0.0001Sv = 0.01 rem = 10 mrem). [Memorize converting units!]
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Rest mass of e- = ?
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0.51MeV
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If a muon has a mass 207 times that of an e-, its mass is equivalent to ? MeV.
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(Rest mass of an electron =0.51MeV. 207x0.51=106MeV)
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A 10MeV ? (photon/electron/neutron/Alpha/Gamma) travels at the greatest speed in a vacuum.
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electron
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(10MeV is the kinetic E of the particle; the lightest particle travels fastest)
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Different Isotopes of the same element will have equal numbers of:
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Protons and Electrons.
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An element is defined by the #of protons in it’s nucleus. Protons & electrons must be equal in # in a neutral atom, so it is the # of neutrons that differs between isotopes of the same element.
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The atom 14/6 C has: (?)electrons, (?)protons & (?)neutrons
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electrons=6, protons=6, neutrons=8
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The subscript is the Atomic # (Z), which is the # of electrons. The # of protons must be = to Z to balance + and – charges. The superscript is the Mass number (A), which is the total # of protons + neutrons, N, in the nucleus. Thus N=A-Z=14-6=8.
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The Atomic # (Z) is the # of (?)
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electrons. The # of protons must be = to Z to balance + and – charges
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The # of protons must be = to Z to balance + and – charges
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The Mass number (A) is the # of (?)
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protons + neutrons, N, in the nucleus. Thus N=A-Z
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The superscript. protons + neutrons, N, in the nucleus. Thus N=A-Z
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Binding Energy (Definition)
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is the energy needed to remove an electron from it’s orbit. It increases with Z and proximity to the nucleus…K>L>M, etc.
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Electron binding energy: Increases/Decreases/Unchanged with Z
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Increases with Z.
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Binding Energy is the energy needed to remove an electron from it’s orbit. It increases with BOTH Z and proximity to the nucleus…K>L>M, etc.
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In heavy nuclei such as U-235, Neutrons are: (Same/Less/More) -vs- Protons
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MORE Neutrons than Protons.
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As the Mass # (A) increases, more neutrons are needed to balance the attraction of all masses (Nucleons) with the repulsion between positively charged protons.
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The chemical properties of the atom are determined by the number of _______ in the ______ shell of an atom
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electrons in the outer shell of an atom
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The max # of electrons allowed in any shell is ?
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2n2 - aka (2 x n) squared, but the max in the outer shell is 8.
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All isotopes of a given element always have the ______ electron configuration.
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same electron configuration
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_______ have the maximum # of electrons in the outer shell.
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Inert gases
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The radioactive source w/a half-life of 6 hours has an activity of 10.0mCi at noon on Monday. The activity at noon on Tuesday is: _____mCi.
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The activity at noon on Tuesday is: 0.625mCi. (Activity after time t = Initial Activity x exp-t(0.693/half-life). t = 10 x 24 (0.693/6). t=0.625mCi. Alternatively, since the time is 4 half-lives, the Activity can be found by multiplying the initial activity by 1/24).
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Activity after time t = Initial Activity x exp-t(0.693/half-life. Alternatively, since the time is 4 half-lives, the Activity can be found by multiplying the initial activity by 1/24). [Memorize half-lives!]
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The half-life of a radionuclide is: ____ the average life? (Same as/Less than/Greater than) (The average life is 1.44 x half-life. The half-life is inversely proportional to λ, and is unaffected by temperature and pressure).
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LESS. (Half-life is LESS than the average life.)
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The half-life is inversely proportional to λ, and is unaffected by temperature and pressure).
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The half-life is _____ to λ?
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The half-life is inversely proportional to λ, and is unaffected by temperature and pressure. (The average life is 1.44 x half-life.)
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(The average life is 1.44 x half-life.)
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In the expression, A=A0 e-λt, λ is: ? (Definition)
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The fraction of atoms decaying per unit of time
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[Memorize Activity formula(s)!]
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Half life=74 days, what is the decay constant? (T1/2 x λ = 0.693; λ=0.693/74; λ=0.0064 per day)
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T1/2 x λ = 0.693; λ=0.693/74; λ=0.0064 per day
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(T1/2 x λ = 0.693; λ=0.693/74; λ=______ per day)
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If the physical half-life (Tp) of a radionuclide is much smaller than it’s biological half-life (Tb), the effective half-life will be closest to: ?
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Tp. (Since 1/Teff = 1/Tp + 1/Tb, if Tp<<<Tb, this is approx = to Tp.)
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(Since 1/Teff = 1/Tp + 1/Tb, if Tp<<<Tb, then _____.) [Review: Tp, Tb, etc]
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Ra-226 decays to Rn-222 by :
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Alpha Decay. (The Mass # (A) decreases by 4 (226 to 222), so this must be Alpha Decay)
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(The Mass # (A) decreases by 4 (226 to 222), so this must be ______) [Review what decays to what and by what means]
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In the decay of 60/27 Co to 60/28 Ni: A ____ of _____ and several ______ ____ occurs via B- Decay.
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A spectrum of electrons and several monoenergetic photons. (Since Z increases by 1, this is an example of Beta minus (B-) Decay, which always emits a spectrum of betas. In this case, they are accompanied by 2 gammas.
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Since Z increases by 1, this is an example of Beta minus (B-) Decay, which always emits _______
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A positron loses energy passing through matter, and eventually combines with an electron, resulting in: ?
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2 photons of equal energy emitted in opposite directions. (The rest masses of 2 particles combine to yield two 0.51 MeV gammas, emitted in opposite directions. In a PET scanner, they are detected by coincidence counters.)
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yields _____. In a PET scanner, they are detected by coincidence counters
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In a PET scanner, two 0.51 MeV gammas, emitted in opposite directions are detected by ?
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coincidence counters.
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Compared to 99Tc, the mass-energy equivalent of 99mTc is: ? (Smaller/Larger/the Same)
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The mass-energy equivalent of 99mTc is Larger than 99Tc. (99mTc decays to 99Tc, emitting a 140keV gamma, so its mass equivalent is Greater by this amount.)
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99mTc decays to 99Tc, emitting a 140keV gamma, so its mass equivalent is _______ (Smaller, Larger, or the Same?)
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5mCi of 99mTc (140keV) are placed inside a lead container. A photon detected outside the container most likely would be: ?
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a Characteristic x-ray.
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The 140keV x-rays could interact w/lead to emit characteristic x-rays. No photons of energy greater than 140keV are present.
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Annihilation radiation is emitted when a ____ & _____combine.
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when a positron & electron combine.
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Cerenkov radiation is emitted when _____ travel very fast in a medium, such as water
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charged particles, travel very fast in a medium, such as water
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The following radioactive transformation AZX →AZ-1Y + γ + υ represents:
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Electron Capture. (As Z decreases by 1, it must be either B+ or Electron Capture. However, no positron is created, so it’s not B+)
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(As Z decreases by 1, it must be either B+ or _______. However, no positron is created, so it’s not B+)
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When Internal Conversion occurs: Z & A ______.
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Z and A remain the same. (Energy is transferred directly to an inner shell electron, which is then ejected.)
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(Energy is transferred directly to an inner shell electron, which is then ejected.)
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Uranium-235, Potassium-40, Carbon-14, Radon-226 are: Naturally/NOT Naturally occuring radionuclides?
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Naturally occurring Radionuclides
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Fluorine-18 is Naturally occuring/ NOT Naturally occuring Radionuclide ?
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Not naturally occurring: (it’s a cyclotron produced positron emitter, used in PET scanning).
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(it’s a cyclotron produced positron emitter, used in PET scanning).
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Ra-226 to radon gas is an example of ____ (& it occurs when a very long-lived radionuclide decays to a short lived daughter.)
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Secular Equilibrium =
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Type of Equilibrium
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An IR-192 source has an Activity of 5.0 X 10(9) Bq. The activity is ____ mCi?
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135 mCi (Since 1Ci=3.7X10(10) Bq, then 5 X 10(9) Bq = [5 X10(9)] / 3.7 X 10(10) = 0.135 Ci = 135 mCi)
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Since 1Ci=3.7X10(10) Bq, then 5 X 10(9) Bq = [5 X10(9)] / 3.7 X 10(10) = ____ Ci, which = ____ mCi
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Exposure Rate (Formula)
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Exposure Rate = Activity x Exposure Rate Constant x 1/d2
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What does NOT improve the heat capacity of an x-ray tube?
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Thermionic Emission
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TE
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What DOES improve the heat capacity of an x-ray tube?
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1) Rotating Anode
2) Small Target Angle 3) Large Focal Spot |
1) ? Anode
2) ? Target 3) ? Focal |
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Thermionic Emission (definition)
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Thermionic Emission: The emission of electrons from the heated filament
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2 Filaments are used in some x-ray tubes because...
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It enables the smallest focal spot to be used - consistent with the kVp/mA setting.
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The Characteristic x-rays emitted from a tungsten target whenn 100keV electrons are fired at it, have energies...
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EQUAL to the differences in BINDING ENERGIES
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The Effective Energy of an x-ray beam:
a) is ~ to the Atomic # (Z) of the target material b) is ~ to the mAs c) is NOT affected by the added filtration d) is = the kVp e) affects subject contrast |
The Effective Energy of an x-ray beam: e) affects contrast
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The Effective Energy of an x-ray beam is (?) of the kVp
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The Effective Energy of an x-ray beam is:
1/2 to 1/3 of the kVp (depending on filtration) |
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If filtration is added, the Effective Energy of an x-ray beam will be:
Increased or Decreased |
If filtration is added, the Effective Energy of an x-ray beam will be INCREASED
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Effective Energy is NOT affected by:
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Effective Energy is NOT affected by:
Atomic # (Z) or mAs |
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Quality of an x-ray beam is not characterized by (?), because beams w/the same kV may be different.
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Quality of an x-ray beam is not characterized by: peak kV (because beams w/the same kV may be different.)
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Beams w/the SAME kV may have DIFFERENT:
a) Filtration b) Half-value layers c) Maximum wavelengths d) Target materials e) All of the above |
e) All of the above:
Filtration Half-value layers Maximum wavelengths Target materials |
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The 2nd HVL of a photon beam is larger for:
a) all x-ray tube generated photons b) E < 100kVp c) Polyenergetic d) Never - it's always Less |
c) Polyenergetic:
Passing thru the 1st HVL hardens the beam, so the 2nd HVL needs to be > than the 1st HVL |
Passing thru the 1st HVL hardens the beam, so the 2nd HVL needs to be > than the 1st HVL
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Which of the following Electromagnetic Radiation has the highest frequency:
a) Infrared b) Gamma c) Radio Waves d) Ultrasound e) Ultraviolet |
b) Gamma has the highest frequency
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Frequency is (Proportional/Inversely proportional) to energy?
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Frequency is:
PROPORTIONAL to Energy. |
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Which of the following is NOT a form of Electromagnetic Radiation:
a) Infrared b) Gamma c) Radio Waves d) Ultrasound e) Ultraviolet |
d) Ultrasound is NOT a form of Electromagnetic Radiation.
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Which of the following is NOT Ionizing Radiation:
a) 2 MHz ultrasound b) Co-60 gammas c) Sr-90 Betas d) 15 MeV photons e) Neutron leakage from a Linac |
a) Ultrasound is NOT a form of Electromagnetic Radiation.
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The energy of a photon Increases as the (?) increases:
a) Amplitude b) Wavelength c) Frequency d) Speed |
Frequency increases as Energy increases
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If the exposure at 50cm from an x-ray target is 10mR. The exposure at 75cm is (?) mR:
a) 0.7 b) 4.4 c) 6.7 d) 15.0 e) 22.5 |
b) 4.4:
I 75 / I 50 = (50/75)squared |
ISL
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In an electromagnetic wave the electric & magnetic waves are oriented at (?) degrees to each other
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90 degrees
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In an electromagnetic wave the electric & magnetic waves are (?) degrees to the direction of propagation
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90 degrees
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A photon of 100 MHz frequency has a wavelength of:
a) 3mm b) 9mm c) 3 cm d) 9cm e) 3m |
A photon of 100 MHz frequency has a wavelength of: 3 meters.
(c=λv); c=speed of light=3x10(8) m/s. v=100x10(6)s-(1) |
c=λv; c=speed of light=3x10(8) m/s.
v=100x10(6)s-(1) |
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A monoenergetic photon beam with linear attenuation coefficient = 0.0693cm(-1) traverses 10 cm of a medium. The fraction of the beam transmitted is:
a) 0.01 b) 0.37 c) 0.50 d) 0.69 e) 0.90 |
fraction transmitted = I/Io = e(-μx).
μ=0.0693cm(-1) x=10cm I/Io = e(-0.693) = 0.5 |
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The mass attenuation coefficients for most materials EXCEPT hydrogen are similar when (?) interactions predominate:
a) Photoelectric b) Compton c) Pair Production d) Photonuclear Disintegration e) |
b) Compton:
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The mass attenuation coefficients are similar for most materials EXCEPT hydrogen. Why different for hydrogen?
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Most materials have approx 1 electron per 2 nucleons (1 proton & 1 neutron). While hydrogen has 1 electron per nucleon (aka...twice the # of electrons per unit mass as most other elements)
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The photoelectric mass attenuation coefficient is proportional to:
a) Z, E b) Z squared, E squared c) Z cubed, E cubed d) Z cubed, E (-)cubed e) Z squared, E (-)squared |
d) The probability increases as Z (cubed), and decreases ~ as 1/E(cubed)
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The process whereby energy is transferred from a photon beam to electrons in the medium is: (?)
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Absorption
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abs
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The process whereby energy is reemitted as photons is: (?)
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Scatter
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scat
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In photoelectric interactions, which is NOT true:
a) K,L, and M characteristic x-rays may be emitted if the photon energy is > the K-shell binding energy b) The photelectron's energy is the energy of the incident photon less the biniding energy of the emitted electron c)The probability is greatest when the photon energy is a little less that the electron binding energy d) In tissue, mos of the released energy is locally absorbed |
NOT true is c) NOT a little less.
The probability is greates when the photon energy is just greater than the electron binding energy |
The probability is greates when the photon energy is just greater than the electron binding energy
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A 70keV photon beam interacts w/an atom whose K-shell binding energy is 5 keV. An electron is emitted w/a kinetic energy of 65 keV. Which is NOT true:
a) Characteristic radiation is emitted b) The 70 keV photon disappers c) The electron will be absorbed within 1cm of its origin in tissue d) This is an example of Compton scattering |
It is NOT: c) an example of Compton scattering.
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This is photoelectric absorption since the product is a 65 keV photoelectron.
Characteristic radiation will be emitted as a reslt of an e- from an outer shell falling into the K-shell vacancy. Electrons interact because of their charg and mass by ionization & excitation along their paths. Electrons path, except in air, is very short. |
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In Compton interactiond, which is true:
a) The photon changes direction but does NOT lose energy b) The e- may acquire any energy fro 0 up to the energy of the incident photon c) e- can be emitted between 0 degrees and 90 degrees to the direction of the incident photon d) a neutrino is emitted |
C) e- can be emitted between 0 degrees and 90 degrees to the direction of the incident photon
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The energy of the incident photon is divided between the scattered photon & recoil e-.
The min scattered Photon Energy @ 180degrees (backwards). The e- acquires its Max Kinetic Energy & travels forward. The Min e- Energy @ 90degrees |
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At 2m away from a patient during fluoroscopy (outside the primary beam), the main dose would be due to:
a) Compton electrons b) Photelectrons c) Compton Scattered photons d) Characteristic x-rays generated in the patient d) Coherent scatter |
c) Compton Scattered photons.
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Even @ low KV, COHERENT scatter is only a small part of the total.
The CHARACTERISTIC x-rays created w/in the patient are very low energy (due to low Z of tissue). COMPTON and PHOTELECTRONS als have short range & are unlikely to leave the body. |
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In Compton scattering, the energy difference between the incident & scattered photons is:
a) Shared equally betw the recoiling nucleus & ejected e- b) Maximized when the photon is scattered @ 180degrees c) Equal to the Binding Energy of the ejected e- d) Always > than 0.51 MeV |
b) Maximized when the photon is scattered @ 180degrees.
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The energy lost by the incident photon is used to eject the e- (binding energy), w/the remainder given as kinetic energy to the electron. The max energy transfer occurs when the photon is backscattered. Nuclear recoil accts for a very small amt of energy.
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The probability per gram of a Compton interaction:
a) Increases as energy Increases b) Is Independent of energy c) Is proportional to Esquared Zsquared d) Is proportional to Zcubed E(-3) e) None of the above |
e) None of the above
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Compton interactions per unit mass are approx INDEPENDENT of Z & DECREASE w/ Increasing energy
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The most probable interaction in soft tissue for a 50 keV photon is:
a) Coherent scatter b) Photoelectric c) Compton d) Pair Production e) Photnuclear disintegration |
c) Compton
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Compton is the most probable between 25 keV and 25 MeV
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A 2.3 MeV photon undergoes Pair Production in tissue. The energy deposited locally is (?) MeV:
a) 2.3 b) 1.79 c) 1.28 d) 0.51 e) None |
c) 1.28:
0.51 x 2 = 1.02 (2.3 - 1.02 = 1.28) |
It takes 2 x 0.51 MeV to create the electron-positron pair. The remaining 1.28 MeV is divided between the two particles as kinetic energy. This kinetic energy is deposited locally and when the positron & e- combine and annihilate, the two 0.51 Mev photons are emitted.
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After a 1.5MeV photon undergoes Pair Production, production of (?) will always occur:
a) a pair of 0.51 MeV photons b) a pair of 0.51 MeV positrons c) a pair of 0.51 MeV electrons d) a single 0.51 MeV photon e) an elecron & positron, each w/kinetic energy of 0.51MeV |
a) a pair of 0.51 MeV photons
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It takes 2 x 0.51 MeV to create the electron-positron pair. The remaining 1.28 MeV is divided between the two particles as kinetic energy. This kinetic energy is deposited locally and when the positron & e- combine and annihilate, the two 0.51 Mev photons are emitted.
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The threshold for Pair Production is (?) MeV:
a) 0.51 b) 1.02 c) 1.53 d) 2.04 |
b) 1.02
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It takes 2 x 0.51 MeV to create the electron-positron pair. The remaining 1.28 MeV is divided between the two particles as kinetic energy. This kinetic energy is deposited locally and when the positron & e- combine and annihilate, the two 0.51 Mev photons are emitted.
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In diagnostic x-ray systems, filters are used to "harden" the beam. The process is mainly due to:
a) Coherent scattering b) Photoelectric Effect c) Compton Effect d) Pair Production e) a, b & c only |
b) Photoelectric Effect
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With the exception of K edges, Photelectric interactions are more likely @ low energy than high energy. After passing thru a filter, the total beam intensity is reduced, but the beam contains a relatively greater # of hig-energy photons than before filtration.
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CT or Hounsfield numers are linearly related to:
a) Mass density b) electron density c) Linear attenuation coefficient d) Mass absorption coefficient e) Effective atomic number |
c) Linear attenuation coefficient
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CT number = 1000 x [(μ material - μ water) / μ water]
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Which of the following loses the greatest amount of energy per unit path length? A 5 Mev ____
a) Electron b) Alpha Particle c) Proton d) Neutron |
b) Alpha Particle
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Energy loss is greatest for the particle w/ the greatest mass & charge
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Directly Ionizing radiation includes all EXCEPT:
a) Electrons b) Positrons c) Neutrons d) Alpah Particles |
c) Neutrons
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Neutrons are not charged particles; they generally interact by transferring their energy to protons or other light nuclei, which then produce dense ionization tracks.
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