Raphex Exam Fully solved & updated (latest version verified
for accuracy) (Questions + Answers) Solved 100% Correct!!
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:
a. radiographic film
b. radiochromic film
c. Al2O3 OSLD
d. LiF thermoluminescents
Energy dependence will be based on Atomic Number
a. A = 42.8
b. A = 6.84
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 measuring surface dose
a. extrapolation chamber
b. farmer chamber
c. plane parallel chamber
d. OSLD chamber
e. film
a. extrapolation chamber
according to AAPM TG 176, the extrapolation chamber is the gold standard for
surface dose measurement
The charge measured by an ionization chamber is __ proportional to the pressure
and ______ proportional to the temperature of the gas in the chamber
directly; inversely
as the pressure increases or the temperature decreases, the density of air in the
chamber will increase, resulting in an increase in charge measured.
_ _______ is NOT suitable for small field dosimetry
a. Film
b. A diode
c. An EPID
d. A Farmer Chamber
e. They are all suitable
d. A Farmer chamber
the active volume, typically 0.6 cc is too large for small field dosimetry (too large
for SRS field sizes)
How often should therapy dosimeters (TD) for MV beams and survey meters (SM)
for performing radiation safety surveys be sent to an accredited lab for
calibration?
TD 2 years; SM 1 year
, Air gap between patient surface and bolus for 6 MV photon beam will result in
a decreased surface dose due to _________
a loss of electron equilibrium
How to determine wedge angle for two-field plan given a gantry angle
gantry angle (HA)
WA = (1/2) * (180 - HA)
The penumbra is sharpest for a photon beam
a. Co-60
b. 6 MV
c. 10 MV
d. 15 MV
e. 18 MV
b. 6 MV
as energy increases, the penumbra gets wider (due to range of the secondary
electrons increasing with energy)
penumbra is wider for Co-60 though due to the source size
for accuracy) (Questions + Answers) Solved 100% Correct!!
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:
a. radiographic film
b. radiochromic film
c. Al2O3 OSLD
d. LiF thermoluminescents
Energy dependence will be based on Atomic Number
a. A = 42.8
b. A = 6.84
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 measuring surface dose
a. extrapolation chamber
b. farmer chamber
c. plane parallel chamber
d. OSLD chamber
e. film
a. extrapolation chamber
according to AAPM TG 176, the extrapolation chamber is the gold standard for
surface dose measurement
The charge measured by an ionization chamber is __ proportional to the pressure
and ______ proportional to the temperature of the gas in the chamber
directly; inversely
as the pressure increases or the temperature decreases, the density of air in the
chamber will increase, resulting in an increase in charge measured.
_ _______ is NOT suitable for small field dosimetry
a. Film
b. A diode
c. An EPID
d. A Farmer Chamber
e. They are all suitable
d. A Farmer chamber
the active volume, typically 0.6 cc is too large for small field dosimetry (too large
for SRS field sizes)
How often should therapy dosimeters (TD) for MV beams and survey meters (SM)
for performing radiation safety surveys be sent to an accredited lab for
calibration?
TD 2 years; SM 1 year
, Air gap between patient surface and bolus for 6 MV photon beam will result in
a decreased surface dose due to _________
a loss of electron equilibrium
How to determine wedge angle for two-field plan given a gantry angle
gantry angle (HA)
WA = (1/2) * (180 - HA)
The penumbra is sharpest for a photon beam
a. Co-60
b. 6 MV
c. 10 MV
d. 15 MV
e. 18 MV
b. 6 MV
as energy increases, the penumbra gets wider (due to range of the secondary
electrons increasing with energy)
penumbra is wider for Co-60 though due to the source size
