Dosegrid/Raphex Review Questions
linear attenuation coefficient - correct answer describes how many photons are attenuated
when travelling through the thickness of a material
mass attenuation coefficient - correct answer tells you how easily something can be penetrated
by radiation (assuming things all have the same density)
The line focus principle is used in diagnostic x-ray tube design in order to: - correct answer
make the apparent focal spot size smaller than the actual focal spot size
What properties of tungsten make it a useful target material in MV linacs? - correct answer
high melting point and high atomic number
Insufficient vacuum inside the x-ray tube can lead to __________. - correct answer tube arcing
The _______ is the positive end of the x-ray tube and the __________ is the negative end. -
correct answer anode, cathode
If you want to increase image quality, you should _______ focal spot size. - correct answer
decrease
The output of an x-ray tube is approximately proportional to: - correct answer square of tube
voltage at a given tube current
Thermionic emission is the release of ________ from a heated filament in the _________. -
correct answer electrons; cathode
In terms of energy spectrum, characteristic x-ray emission is ________ and bremsstrahlung x-
ray emission is ____________. - correct answer discrete; continuous
The factor that results in the largest increase in x-ray output from an x-ray tube is: - correct
answer double the kV
The production of characteristic x-rays competes directly with production of: - correct answer
Auger electrons
The effective energy of an x-ray beam can be increased by: - correct answer increasing the
filtration
The linear attenuation coefficient of a beam is .05cm-1. The HVL is: - correct answer 13.9 cm
If the linear attenuation coefficient is 1.5cm-1, the HVL is _____ cm? - correct answer 0.462 cm
Standards defining the minimum necessary amount of inherent filtration to be used in x-ray
tubes are intended to _________. - correct answer reduce patient skin dose
Compared to radiowaves, ultraviolet waves have a _________ frequency and ________
wavelength. - correct answer higher; shorter
,Neutrons have a higher quality factor than electrons because: - correct answer They transfer
energy to protons, which have a high LET
What would be an efficient absorber of neutrons? - correct answer borated polyethylene
What is the quality factor of x-rays/gamma rays? - correct answer 1
Which of these types of radiation is ionizing? - correct answer gamma rays
Which modality has the highest neutron contamination? - correct answer 15 MV
In a linear accelerator, to produce the same dose rate for a 15 MV x-ray beam as for a 6 MV x-
ray beam, the electron current in the accelerating cavity must be: - correct answer Higher for 6
MV than for 15 MV
In a linac, to produce the same dose rate for a 15 MV x-ray beam as for a 15 MeV electron
beam, the electron current in the accelerating cavity must be: - correct answer Lower for
electron treatment than for photon treatment
For a 15 MeV electron beam, most of the x-ray contamination comes from electron interactions
in the: - correct answer Electron applicators and collimators
If the filtration of a diagnostic x-ray beam is increased, the resulting beam will have: - correct
answer Lower dose rate and greater HVL
Which of the following does NOT occur when a linac is changed from x-ray mode to electron
mode? - correct answer The monitor chamber is removed
Flattening filters are designed to optimally flatten the beam at a depth of: - correct answer 10
cm
Primary Collimator in a linear accelerator is located before: - correct answer Flattening filter
In which of the following is the microwave power absorbed at the end of a waveguide? - correct
answer Traveling waveguide
Which of the following will increase the maximum x-ray dose rate of a linear accelerator? -
correct answer all of the above
Which of the following must be changed for different energy electron beams on a linac? -
correct answer bending magnet current
Compared to a flattened 6 MV beam, a FFF beam will have ________ average energy and
_______ dmax depth. - correct answer decreased; decreased
The accelerator component that injects electrons into the linear accelerator is: - correct answer
an electron gun
One function of the ion chamber in the linac is to monitor: - correct answer field symmetry
, Which of these units would treat at an SSD of about 50 cm and energies 150-500 kv? - correct
answer orthovoltage
What is the depth of maximum dose for a Co-60 unit? - correct answer 0.5 cm
An electron field is planned at 100 SSD but must be treated at 105 SSD. The size of the cutout
should be _____ by about ______%. - correct answer decreased; 5
The advantage of gated radiotherapy for lung treatment is: - correct answer reduced treatment
margin
The approximate dose from a kV cone-beam CT is in the range of _____mGy - correct answer 1-
40
One benefit of full-fan, half-scan, CBCT is: - correct answer higher spatial resolution
Transfer of CT images between different vendors' treatment planning systems is facilitated by
the _____ standard. - correct answer DICOM
In IMRT optimization, the value of the cost (or objective) function quantitatively represents
____________ - correct answer deviation from the desired dose distribution
IMRT dose calculations can be performed using any of the following EXCEPT ___________ -
correct answer None of the above is true
__________ generates the IMRT fluence and ________ generates the actual MLC pattern that
can actualize the photon fluence. - correct answer Optimization; leaf sequencing
Which of the following is TRUE regarding the relative contributions of systematic and random
errors to the calculation of the setup margin? - correct answer Systematic errors have greater
weight.
In DVH analysis, the D100% refers to the _______ dose. - correct answer minimum
The primary role of the beam spoiler in TBI is to: - correct answer increase skin dose
The patient positioning, beam arrangement, and electron energies used in TSET are designed to
minimize: - correct answer x-ray contamination
MV photon beam quality should be specified by its PDD at what depth? - correct answer 10 cm
depth
Electron beam quality should be specified by what depth? - correct answer R50
For a fixed radiation dose to an open-air ion chamber, the chamber reading ________ with
temperature and _________ with pressure. - correct answer decreases, increases
When measuring the HVL of an x-ray beam, a narrow beam must be used because: - correct
answer The beam must be smaller than the detector
linear attenuation coefficient - correct answer describes how many photons are attenuated
when travelling through the thickness of a material
mass attenuation coefficient - correct answer tells you how easily something can be penetrated
by radiation (assuming things all have the same density)
The line focus principle is used in diagnostic x-ray tube design in order to: - correct answer
make the apparent focal spot size smaller than the actual focal spot size
What properties of tungsten make it a useful target material in MV linacs? - correct answer
high melting point and high atomic number
Insufficient vacuum inside the x-ray tube can lead to __________. - correct answer tube arcing
The _______ is the positive end of the x-ray tube and the __________ is the negative end. -
correct answer anode, cathode
If you want to increase image quality, you should _______ focal spot size. - correct answer
decrease
The output of an x-ray tube is approximately proportional to: - correct answer square of tube
voltage at a given tube current
Thermionic emission is the release of ________ from a heated filament in the _________. -
correct answer electrons; cathode
In terms of energy spectrum, characteristic x-ray emission is ________ and bremsstrahlung x-
ray emission is ____________. - correct answer discrete; continuous
The factor that results in the largest increase in x-ray output from an x-ray tube is: - correct
answer double the kV
The production of characteristic x-rays competes directly with production of: - correct answer
Auger electrons
The effective energy of an x-ray beam can be increased by: - correct answer increasing the
filtration
The linear attenuation coefficient of a beam is .05cm-1. The HVL is: - correct answer 13.9 cm
If the linear attenuation coefficient is 1.5cm-1, the HVL is _____ cm? - correct answer 0.462 cm
Standards defining the minimum necessary amount of inherent filtration to be used in x-ray
tubes are intended to _________. - correct answer reduce patient skin dose
Compared to radiowaves, ultraviolet waves have a _________ frequency and ________
wavelength. - correct answer higher; shorter
,Neutrons have a higher quality factor than electrons because: - correct answer They transfer
energy to protons, which have a high LET
What would be an efficient absorber of neutrons? - correct answer borated polyethylene
What is the quality factor of x-rays/gamma rays? - correct answer 1
Which of these types of radiation is ionizing? - correct answer gamma rays
Which modality has the highest neutron contamination? - correct answer 15 MV
In a linear accelerator, to produce the same dose rate for a 15 MV x-ray beam as for a 6 MV x-
ray beam, the electron current in the accelerating cavity must be: - correct answer Higher for 6
MV than for 15 MV
In a linac, to produce the same dose rate for a 15 MV x-ray beam as for a 15 MeV electron
beam, the electron current in the accelerating cavity must be: - correct answer Lower for
electron treatment than for photon treatment
For a 15 MeV electron beam, most of the x-ray contamination comes from electron interactions
in the: - correct answer Electron applicators and collimators
If the filtration of a diagnostic x-ray beam is increased, the resulting beam will have: - correct
answer Lower dose rate and greater HVL
Which of the following does NOT occur when a linac is changed from x-ray mode to electron
mode? - correct answer The monitor chamber is removed
Flattening filters are designed to optimally flatten the beam at a depth of: - correct answer 10
cm
Primary Collimator in a linear accelerator is located before: - correct answer Flattening filter
In which of the following is the microwave power absorbed at the end of a waveguide? - correct
answer Traveling waveguide
Which of the following will increase the maximum x-ray dose rate of a linear accelerator? -
correct answer all of the above
Which of the following must be changed for different energy electron beams on a linac? -
correct answer bending magnet current
Compared to a flattened 6 MV beam, a FFF beam will have ________ average energy and
_______ dmax depth. - correct answer decreased; decreased
The accelerator component that injects electrons into the linear accelerator is: - correct answer
an electron gun
One function of the ion chamber in the linac is to monitor: - correct answer field symmetry
, Which of these units would treat at an SSD of about 50 cm and energies 150-500 kv? - correct
answer orthovoltage
What is the depth of maximum dose for a Co-60 unit? - correct answer 0.5 cm
An electron field is planned at 100 SSD but must be treated at 105 SSD. The size of the cutout
should be _____ by about ______%. - correct answer decreased; 5
The advantage of gated radiotherapy for lung treatment is: - correct answer reduced treatment
margin
The approximate dose from a kV cone-beam CT is in the range of _____mGy - correct answer 1-
40
One benefit of full-fan, half-scan, CBCT is: - correct answer higher spatial resolution
Transfer of CT images between different vendors' treatment planning systems is facilitated by
the _____ standard. - correct answer DICOM
In IMRT optimization, the value of the cost (or objective) function quantitatively represents
____________ - correct answer deviation from the desired dose distribution
IMRT dose calculations can be performed using any of the following EXCEPT ___________ -
correct answer None of the above is true
__________ generates the IMRT fluence and ________ generates the actual MLC pattern that
can actualize the photon fluence. - correct answer Optimization; leaf sequencing
Which of the following is TRUE regarding the relative contributions of systematic and random
errors to the calculation of the setup margin? - correct answer Systematic errors have greater
weight.
In DVH analysis, the D100% refers to the _______ dose. - correct answer minimum
The primary role of the beam spoiler in TBI is to: - correct answer increase skin dose
The patient positioning, beam arrangement, and electron energies used in TSET are designed to
minimize: - correct answer x-ray contamination
MV photon beam quality should be specified by its PDD at what depth? - correct answer 10 cm
depth
Electron beam quality should be specified by what depth? - correct answer R50
For a fixed radiation dose to an open-air ion chamber, the chamber reading ________ with
temperature and _________ with pressure. - correct answer decreases, increases
When measuring the HVL of an x-ray beam, a narrow beam must be used because: - correct
answer The beam must be smaller than the detector
