Raphex Exam Fully solved & updated (latest
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Terms in this set (82)
In the equation for radioactive the fraction of atoms that decay per unit time
decay, lambda represents _________
Purpose of rounded leaf ends for keep the geometric penumbra relatively constant
MLCs for different leaf positions
Neutron contamination is greatest c. 18 MV photon
in a _______ beam remember neutrons are produced through
a. 6 MV photon photon interactions, begin happening above 10
b. 10 MV photon MV photons
c. 18 MV photon
d. 6 MeV electron
e. 20 MeV electron
Loss of charged particle equilibrium < 5x5; >= 15 MV
is greatest in lung radiotherapy for effect is greater for higher photon energies since
field sizes _______ cm2 and photon the average energy of the secondary electrons is
energies _______ MV greater. effect is greater for small field sizes,
harder to maintain CPE in small space
,What is the relationship between HVL1 < HVL2 always
HVL1 and HVL2 for a polyenergetic As a polyenergetic kV photon beam traverses a
kV photon beam material, lower-energy photons will be
preferentially attenuated. Therefore, as the beam
travels farther into a material, it will become
hardened and its average energy will increase.
Therefore, the HVL will increase as well.
Compton scattering angles for MAX ENERGY TRANSFER --> electron scattered 0
minimum and maximum energy degrees (forward) and the photon is scattered at
transference 180 degrees (backward)
MIN ENERGY TRANSFER --> electron scattered at
90 (sideways) and photon is scattered at 0
degrees (forward), no energy is transferred to the
electron
NOTE: all of the photon energy cannot be
transferred to the electron, must always be some
energy available for the scattered photon.
what is the relationship between the u_tr/ρ ≤ u_en/ρ always
mass energy transfer coefficient u_tr/ρ includes radiative losses, u_en/ρ does not
(u_tr/ρ) and the mass energy
absorption coefficient (u_en/ρ)
The quantity f_med (or f-factor) roentgen-to-rad conversion factor
0.876 * (u_en/ρ)air/(u_en/ρ)med
as such, function of both medium density and
photon energy
KERMA is defined as _______ the energy per unit mass transferred from
incident photons to charged particles in the
medium
(energy of charged particles liberated by
indirectly ionizing radiation)
, Energy dependence of dosimeters: Energy dependence will be based on Atomic
a. radiographic film Number
b. radiochromic film a. A = 42.8
c. Al2O3 OSLD b. A = 6.84
d. LiF thermoluminescents c. A = 11.2
d. A = 8.2
In the kV range, radiochromic film will have the
least energy dependence (as in the Photoelectric
effect range, attenuation is proportional to Z^3)
_____________ is the most accurate for a. extrapolation chamber
measuring surface dose according to AAPM TG 176, the extrapolation
a. extrapolation chamber chamber is the gold standard for surface dose
b. farmer chamber measurement
c. plane parallel chamber
d. OSLD chamber
e. film
The charge measured by an directly; inversely
ionization chamber is ___________ as the pressure increases or the temperature
proportional to the pressure and decreases, the density of air in the chamber will
__________ proportional to the increase, resulting in an increase in charge
temperature of the gas in the measured.
chamber
_____________ is NOT suitable for small d. A Farmer chamber
field dosimetry the active volume, typically 0.6 cc is too large for
a. Film small field dosimetry (too large for SRS field
b. A diode sizes)
c. An EPID
d. A Farmer Chamber
e. They are all suitable
version verified for accuracy) (Questions +
Answers) Solved 100% Correct!!
Save
Terms in this set (82)
In the equation for radioactive the fraction of atoms that decay per unit time
decay, lambda represents _________
Purpose of rounded leaf ends for keep the geometric penumbra relatively constant
MLCs for different leaf positions
Neutron contamination is greatest c. 18 MV photon
in a _______ beam remember neutrons are produced through
a. 6 MV photon photon interactions, begin happening above 10
b. 10 MV photon MV photons
c. 18 MV photon
d. 6 MeV electron
e. 20 MeV electron
Loss of charged particle equilibrium < 5x5; >= 15 MV
is greatest in lung radiotherapy for effect is greater for higher photon energies since
field sizes _______ cm2 and photon the average energy of the secondary electrons is
energies _______ MV greater. effect is greater for small field sizes,
harder to maintain CPE in small space
,What is the relationship between HVL1 < HVL2 always
HVL1 and HVL2 for a polyenergetic As a polyenergetic kV photon beam traverses a
kV photon beam material, lower-energy photons will be
preferentially attenuated. Therefore, as the beam
travels farther into a material, it will become
hardened and its average energy will increase.
Therefore, the HVL will increase as well.
Compton scattering angles for MAX ENERGY TRANSFER --> electron scattered 0
minimum and maximum energy degrees (forward) and the photon is scattered at
transference 180 degrees (backward)
MIN ENERGY TRANSFER --> electron scattered at
90 (sideways) and photon is scattered at 0
degrees (forward), no energy is transferred to the
electron
NOTE: all of the photon energy cannot be
transferred to the electron, must always be some
energy available for the scattered photon.
what is the relationship between the u_tr/ρ ≤ u_en/ρ always
mass energy transfer coefficient u_tr/ρ includes radiative losses, u_en/ρ does not
(u_tr/ρ) and the mass energy
absorption coefficient (u_en/ρ)
The quantity f_med (or f-factor) roentgen-to-rad conversion factor
0.876 * (u_en/ρ)air/(u_en/ρ)med
as such, function of both medium density and
photon energy
KERMA is defined as _______ the energy per unit mass transferred from
incident photons to charged particles in the
medium
(energy of charged particles liberated by
indirectly ionizing radiation)
, Energy dependence of dosimeters: Energy dependence will be based on Atomic
a. radiographic film Number
b. radiochromic film a. A = 42.8
c. Al2O3 OSLD b. A = 6.84
d. LiF thermoluminescents c. A = 11.2
d. A = 8.2
In the kV range, radiochromic film will have the
least energy dependence (as in the Photoelectric
effect range, attenuation is proportional to Z^3)
_____________ is the most accurate for a. extrapolation chamber
measuring surface dose according to AAPM TG 176, the extrapolation
a. extrapolation chamber chamber is the gold standard for surface dose
b. farmer chamber measurement
c. plane parallel chamber
d. OSLD chamber
e. film
The charge measured by an directly; inversely
ionization chamber is ___________ as the pressure increases or the temperature
proportional to the pressure and decreases, the density of air in the chamber will
__________ proportional to the increase, resulting in an increase in charge
temperature of the gas in the measured.
chamber
_____________ is NOT suitable for small d. A Farmer chamber
field dosimetry the active volume, typically 0.6 cc is too large for
a. Film small field dosimetry (too large for SRS field
b. A diode sizes)
c. An EPID
d. A Farmer Chamber
e. They are all suitable
