Dosimetry |318 questions with verified answers
_____ is not required after an HDR source exchange?
a) Percent depth dose
b) Source positioning
c) Source strength
d) Timer Linearity
e) A radiation safety survey Ans✓✓✓ a) Percent depth dose
-Technique uses 3D images of the tumor.
-Multiple beams can be shaped exactly (conform) to the contour of the
tumor volume. Ans✓✓✓ Conformal radiation therapy
-Treat the gross tumor volume only.
-small volumes with high doses Ans✓✓✓ Boost fields
"Skin sparing" is reduced in photon beams by all of the following
except:
a) Using bolus
b) Treating through a plaster cast
c) Using a beam spoiler
d) Treating tissue under a skin fold
e) Increasing photon energy Ans✓✓✓ e) Increasing photon energy
,1 Gy is equal to:
a) 100 erg/g
b) 1 J/kg
c) 10 rads
d) 1000 rads Ans✓✓✓ b) 1 J/kg
A bite block is sometimes inserted between the patient's teeth
because:
a) It helps the patient keep his or her mouth open during the
treatment for easier breathing.
b) It helps the patient keep his or her mouth open during the
treatment so more of the oral mucosa can be excluded from the
radiation field
c) It is part of the immobilization system and it keeps the patient from
talking while being treated
d) It helps in extending the patient's chin more so an anterior field can
enter inferior to the eyes Ans✓✓✓ b) It helps the patient keep his or
her mouth open during the treatment so more of the oral mucosa can
be excluded from the radiation field
A bolus is commonly employed during electron therapies for all the
following except:
a) Increasing skin dose
b) Filling in for missing tissues
,c) Reducing electron penetration
d) Reducing the effect of photons in the beam Ans✓✓✓ d) Reducing
the effect of photons in the beam
A brachytherapy source is encapsulated to:
a) produce bremsstrahlung in the encapsulation wall
b) reduces the intensity of the brachytherapy source
c) increase the useful life of the source
d) contain radioactivity and stop particles other than gamma in
delivering tumor dose Ans✓✓✓ d) contain radioactivity and stop
particles other than gamma in delivering tumor dose
A computer-generated treatment plan is checked with hand
calculations. The plan is for an isocentric wedged pair. The minimum
data necessary to check the MU by hand is: (Select all that apply)
a) TMR tables
b) PDD tables
c) Wedge factors
d) Output at dmax, SAD
e) Dose per beam at isocenter Ans✓✓✓ a) TMR tables
c) Wedge factors
d) Output at dmax, SAD
e) Dose per beam at isocenter
, A defibrillator/pacemaker is 2 cm outside the edge of a treatment field.
The main advantage of treating with a 6 MV rather than an 18 MV
photon beam is:
a) lower scatter dose to the device
b) lower photon energy
c) lower neutron dose
d) higher dose rate Ans✓✓✓ c) lower neutron dose
A dose volume histogram (DVH) does not contain information about
the ____ within an organ.
a) range of doses
b) spatial distribution of dose
c) mean dose
d) all of the above Ans✓✓✓ b) spatial distribution of dose
A high energy x-ray beam is incident on the surface of the water in a
water tank. Indicate which of the following statements is correct.
a) Maximum dose is at the water surface
b) Maximum dose is at a depth dependent on the x-ray energy.
c) Maximum dose is always at a fixed depth, independent of x-ray
energy.
_____ is not required after an HDR source exchange?
a) Percent depth dose
b) Source positioning
c) Source strength
d) Timer Linearity
e) A radiation safety survey Ans✓✓✓ a) Percent depth dose
-Technique uses 3D images of the tumor.
-Multiple beams can be shaped exactly (conform) to the contour of the
tumor volume. Ans✓✓✓ Conformal radiation therapy
-Treat the gross tumor volume only.
-small volumes with high doses Ans✓✓✓ Boost fields
"Skin sparing" is reduced in photon beams by all of the following
except:
a) Using bolus
b) Treating through a plaster cast
c) Using a beam spoiler
d) Treating tissue under a skin fold
e) Increasing photon energy Ans✓✓✓ e) Increasing photon energy
,1 Gy is equal to:
a) 100 erg/g
b) 1 J/kg
c) 10 rads
d) 1000 rads Ans✓✓✓ b) 1 J/kg
A bite block is sometimes inserted between the patient's teeth
because:
a) It helps the patient keep his or her mouth open during the
treatment for easier breathing.
b) It helps the patient keep his or her mouth open during the
treatment so more of the oral mucosa can be excluded from the
radiation field
c) It is part of the immobilization system and it keeps the patient from
talking while being treated
d) It helps in extending the patient's chin more so an anterior field can
enter inferior to the eyes Ans✓✓✓ b) It helps the patient keep his or
her mouth open during the treatment so more of the oral mucosa can
be excluded from the radiation field
A bolus is commonly employed during electron therapies for all the
following except:
a) Increasing skin dose
b) Filling in for missing tissues
,c) Reducing electron penetration
d) Reducing the effect of photons in the beam Ans✓✓✓ d) Reducing
the effect of photons in the beam
A brachytherapy source is encapsulated to:
a) produce bremsstrahlung in the encapsulation wall
b) reduces the intensity of the brachytherapy source
c) increase the useful life of the source
d) contain radioactivity and stop particles other than gamma in
delivering tumor dose Ans✓✓✓ d) contain radioactivity and stop
particles other than gamma in delivering tumor dose
A computer-generated treatment plan is checked with hand
calculations. The plan is for an isocentric wedged pair. The minimum
data necessary to check the MU by hand is: (Select all that apply)
a) TMR tables
b) PDD tables
c) Wedge factors
d) Output at dmax, SAD
e) Dose per beam at isocenter Ans✓✓✓ a) TMR tables
c) Wedge factors
d) Output at dmax, SAD
e) Dose per beam at isocenter
, A defibrillator/pacemaker is 2 cm outside the edge of a treatment field.
The main advantage of treating with a 6 MV rather than an 18 MV
photon beam is:
a) lower scatter dose to the device
b) lower photon energy
c) lower neutron dose
d) higher dose rate Ans✓✓✓ c) lower neutron dose
A dose volume histogram (DVH) does not contain information about
the ____ within an organ.
a) range of doses
b) spatial distribution of dose
c) mean dose
d) all of the above Ans✓✓✓ b) spatial distribution of dose
A high energy x-ray beam is incident on the surface of the water in a
water tank. Indicate which of the following statements is correct.
a) Maximum dose is at the water surface
b) Maximum dose is at a depth dependent on the x-ray energy.
c) Maximum dose is always at a fixed depth, independent of x-ray
energy.
