MDCB questions and answers Graded A+
For a 4-fld box techn, which of the following will deliver the lower dose to the
femoral heads? - Correct answer-100 SSD, equal dmax dose to all fields
SSD= less hot spots
Which of the following can be classified as indirectly ionizing radiaiton? - Correct
answer-Photons
Also neutrons, x-ray and gamma rays
The presence of a shoulder on the survival curve of most mammalian cells
indicates which of the following? - Correct answer-a reduced efficiency of cell
killing at low doses
When opposing lateral fields to the pharynx are abutted at midline to the anterior
field to the suproclavicular fossae, overdose in the cord may be avoided by -
Correct answer-a small block over the cord in the inf post corner of both lateral
fields
In Photoelectric interactions - Correct answer-the entire energy of the incident
photon is absorbed by the resulting electron
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,Film badges used for personnel monitoring contain filters that are used to: -
Correct answer-fitler info about beam quality and energies
Giving too much radiation to which of the following can lead to xerostomia -
Correct answer-base of tongue
The inguinal lymph nodes are located at a depth of - Correct answer-2-18 cm from
the anterior skin surface and are dependent on the pt's size
The contrast resolution for a tx planning CT scan can be described as a - Correct
answer-measure of the ability to detect objects with small differences in hounsfield
units
a small area of high density near the surface of hte pt would have the greatest
impact on the dose near the edge of the high density are with: - Correct answer-a
single 20 MeV electron field
-^energy ^ surface dose
Mass attenuation coefficient depends on the - Correct answer-thickness of the
material being atttenuated
The binding energy of the nucleus - Correct answer-represents a mass defect in the
nucleus
-binding energy of nucleus is proportional to the stability of a nucleus
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, Accuracy for radiation therapy tx require accuracy within: - Correct answer-+/- 3%
daily output +/- 3%
the value for the Ngas calibration factor for an ioniziation chamber will depend on
the: - Correct answer-composition of the chamber wall
Which are the following descriptors of characteristic x-rays or brems radiation is
true? - Correct answer-Characteristic x-rays are produced following ionization
-ionization is having enough energy to eject an electron. When it's ejected then a
characteristic x-ray is produced b/c an electron falls into then empty place
According to AAPM TG report #142, when performing periodic linac quality
assurance procedures, which of the following is the acceptable tolerance for
electron flatness - Correct answer-3%
Flatness-3%
an individual receives a dose of 0.1 cGy from a gamma source and 0.05cGy from
neutrons. The dose equivalent from both radiation sources is? - Correct answer-
0.1x1+0.05x20=1.1cGy =11 mSv
For quality assurance of brachytherapy tx planning computers, the dose rates
should agree with published data tables to which of the following degrees? -
Correct answer-+/-2
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
For a 4-fld box techn, which of the following will deliver the lower dose to the
femoral heads? - Correct answer-100 SSD, equal dmax dose to all fields
SSD= less hot spots
Which of the following can be classified as indirectly ionizing radiaiton? - Correct
answer-Photons
Also neutrons, x-ray and gamma rays
The presence of a shoulder on the survival curve of most mammalian cells
indicates which of the following? - Correct answer-a reduced efficiency of cell
killing at low doses
When opposing lateral fields to the pharynx are abutted at midline to the anterior
field to the suproclavicular fossae, overdose in the cord may be avoided by -
Correct answer-a small block over the cord in the inf post corner of both lateral
fields
In Photoelectric interactions - Correct answer-the entire energy of the incident
photon is absorbed by the resulting electron
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,Film badges used for personnel monitoring contain filters that are used to: -
Correct answer-fitler info about beam quality and energies
Giving too much radiation to which of the following can lead to xerostomia -
Correct answer-base of tongue
The inguinal lymph nodes are located at a depth of - Correct answer-2-18 cm from
the anterior skin surface and are dependent on the pt's size
The contrast resolution for a tx planning CT scan can be described as a - Correct
answer-measure of the ability to detect objects with small differences in hounsfield
units
a small area of high density near the surface of hte pt would have the greatest
impact on the dose near the edge of the high density are with: - Correct answer-a
single 20 MeV electron field
-^energy ^ surface dose
Mass attenuation coefficient depends on the - Correct answer-thickness of the
material being atttenuated
The binding energy of the nucleus - Correct answer-represents a mass defect in the
nucleus
-binding energy of nucleus is proportional to the stability of a nucleus
©COPYRIGHT 2025, ALL RIGHTS RESERVED 2
, Accuracy for radiation therapy tx require accuracy within: - Correct answer-+/- 3%
daily output +/- 3%
the value for the Ngas calibration factor for an ioniziation chamber will depend on
the: - Correct answer-composition of the chamber wall
Which are the following descriptors of characteristic x-rays or brems radiation is
true? - Correct answer-Characteristic x-rays are produced following ionization
-ionization is having enough energy to eject an electron. When it's ejected then a
characteristic x-ray is produced b/c an electron falls into then empty place
According to AAPM TG report #142, when performing periodic linac quality
assurance procedures, which of the following is the acceptable tolerance for
electron flatness - Correct answer-3%
Flatness-3%
an individual receives a dose of 0.1 cGy from a gamma source and 0.05cGy from
neutrons. The dose equivalent from both radiation sources is? - Correct answer-
0.1x1+0.05x20=1.1cGy =11 mSv
For quality assurance of brachytherapy tx planning computers, the dose rates
should agree with published data tables to which of the following degrees? -
Correct answer-+/-2
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
