MDCB EXAM QUESTIONS AND ANSWERS. A+ GRADED
GUIDE.
Rule of thumb for proton attenuation?
Protons will lose about 10 MeV per cm
Typical treatment energy range for protons?
From 80 MeV to 250 MeV
What are the three dominant photon interactions in radiation oncology?
Photoelectric Effect, Compton Scattering (incoherent scattering), and Pair Production
What determines the energy of a released electron during the photoelectric effect?
Energy of electron = energy of incoming photon - binding energy
The resulting characteristic x-ray will have an energy equal to the difference in binding energies between
energy levels
What is the maximum photon energy when the photon is released at 90 degrees in Compton
scattering?
Max energy of 0.511 MeV
What is the maximum photon energy when the photon is released at 180 degrees in Compton
scattering?
Max energy of 0.255 MeV
What is the minimum energy required for pair production to occur?
Minimum energy of 1.022 MeV
Enough energy to create a positron and electron. Minimum for triplet production is 2X so 2.044 MeV
Which MRI magnet can be turned on and off to acquire the images? Bore magnet or Gradient magnet?
Gradient magnet
Which MRI magnet is ALWAYS on and is identified by the strength of the magnet (1.5 Tesla or 3.0
Tesla)? Bore magnet or Gradient magnet?
Bore magnet
Which machine characteristics are used in proton therapy to accelerate protons to treatment/therapy
energies?
Synchrotron / Cyclotron / Synchrocyclotron
What is the beam line in regards to proton treatment and what is the purpose of it?
, A long line of magnets used to steer the protons to treatment rooms
How is the readout on TLD (thermoluminescent dosimeters/diodes) achieved?
Photons are given off once heated
How is the readout on OSL dosimeters achieved?
Photons are given off once illuminated
What material are OSLD made of?
Aluminum Oxide
Is an ion chamber considered an absolute or relative detector?
Absolute detector
Which imaging modality provides physical information about patient tissue using HU (Hounsfield
Units)?
CT
Which imaging modality provides functional information about patient tissues regarding chemical
activity?
PET
Which imaging modality provides best anatomical information in regard to soft tissues?
MRI
Which imaging modality provides anatomical information regarding the boundaries between tissues?
Ultrasound
Which imaging modality uses backprojection to capture and reconstruct images?
CT
Which imaging modality can distinguish large differences between electron densities but cannot
determine different types of soft tissues?
CT
Which imaging modality uses radioactive tracers that bind to glucose resulting in a poor resolution
"heat map" image?
PET
Which imaging modality is non-ionizing and uses pulse sequences to dictate scan timing that results in
high resultion images?
MRI
GUIDE.
Rule of thumb for proton attenuation?
Protons will lose about 10 MeV per cm
Typical treatment energy range for protons?
From 80 MeV to 250 MeV
What are the three dominant photon interactions in radiation oncology?
Photoelectric Effect, Compton Scattering (incoherent scattering), and Pair Production
What determines the energy of a released electron during the photoelectric effect?
Energy of electron = energy of incoming photon - binding energy
The resulting characteristic x-ray will have an energy equal to the difference in binding energies between
energy levels
What is the maximum photon energy when the photon is released at 90 degrees in Compton
scattering?
Max energy of 0.511 MeV
What is the maximum photon energy when the photon is released at 180 degrees in Compton
scattering?
Max energy of 0.255 MeV
What is the minimum energy required for pair production to occur?
Minimum energy of 1.022 MeV
Enough energy to create a positron and electron. Minimum for triplet production is 2X so 2.044 MeV
Which MRI magnet can be turned on and off to acquire the images? Bore magnet or Gradient magnet?
Gradient magnet
Which MRI magnet is ALWAYS on and is identified by the strength of the magnet (1.5 Tesla or 3.0
Tesla)? Bore magnet or Gradient magnet?
Bore magnet
Which machine characteristics are used in proton therapy to accelerate protons to treatment/therapy
energies?
Synchrotron / Cyclotron / Synchrocyclotron
What is the beam line in regards to proton treatment and what is the purpose of it?
, A long line of magnets used to steer the protons to treatment rooms
How is the readout on TLD (thermoluminescent dosimeters/diodes) achieved?
Photons are given off once heated
How is the readout on OSL dosimeters achieved?
Photons are given off once illuminated
What material are OSLD made of?
Aluminum Oxide
Is an ion chamber considered an absolute or relative detector?
Absolute detector
Which imaging modality provides physical information about patient tissue using HU (Hounsfield
Units)?
CT
Which imaging modality provides functional information about patient tissues regarding chemical
activity?
PET
Which imaging modality provides best anatomical information in regard to soft tissues?
MRI
Which imaging modality provides anatomical information regarding the boundaries between tissues?
Ultrasound
Which imaging modality uses backprojection to capture and reconstruct images?
CT
Which imaging modality can distinguish large differences between electron densities but cannot
determine different types of soft tissues?
CT
Which imaging modality uses radioactive tracers that bind to glucose resulting in a poor resolution
"heat map" image?
PET
Which imaging modality is non-ionizing and uses pulse sequences to dictate scan timing that results in
high resultion images?
MRI
