MDCB questions
For a 4-fld box techn, which of the following will deliver the lower dose to the femoral
heads? - answer100 SSD, equal dmax dose to all fields
SSD= less hot spots
Which of the following can be classified as indirectly ionizing radiaiton? -
answerPhotons
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? - answera 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 - answera small
block over the cord in the inf post corner of both lateral fields
In Photoelectric interactions - answerthe entire energy of the incident photon is
absorbed by the resulting electron
Film badges used for personnel monitoring contain filters that are used to: - answerfitler
info about beam quality and energies
Giving too much radiation to which of the following can lead to xerostomia - answerbase
of tongue
The inguinal lymph nodes are located at a depth of - answer2-18 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 -
answermeasure 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: - answera single 20 MeV
electron field
-^energy ^ surface dose
Mass attenuation coefficient depends on the - answerthickness of the material being
atttenuated
The binding energy of the nucleus - answerrepresents a mass defect in the nucleus
-binding energy of nucleus is proportional to the stability of a nucleus
, Accuracy for radiation therapy tx require accuracy within: - answer+/- 3%
daily output +/- 3%
the value for the Ngas calibration factor for an ioniziation chamber will depend on the: -
answercomposition of the chamber wall
Which are the following descriptors of characteristic x-rays or brems radiation is true? -
answerCharacteristic 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 -
answer3%
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? -
answer0.1x1+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? - answer+/-2
The expected accuracy of tx planning systems that perfrom brachytherapy dose calc's
should be within - answer+/-5%
The number of nuclei decaying per second is expresssed in terms of their? -
answeractivity
Prior to tx h&n pts with IMRT, a 3 field techn was used. Choose the best option to keep
the cord dose under cord tolerance when total rx dose would normally go higher than
50Gy - answerreduce lateral fields post and add an electron beam fields
The adv fo an electron beam over kilovoltage x-ray beam for tx of superficial tumors is -
answerdecrease dose to bone
The five year survival rate for a pancreatic tumor tx with primary radiation is? - answer0-
5%
If the exposure rate constant is 0.87 rcm^2hr^-1mCi^-1 and the average pt transmission
factor is 0.20, the exposure rate at 12.5cm for a pt who has been injected with 20 mCi of
Tc99m is - answerActivity x dose rate/d^2
0.87x.20x20/12.5^2= 0.0223R/hr-22.3mR/hr
For a 4-fld box techn, which of the following will deliver the lower dose to the femoral
heads? - answer100 SSD, equal dmax dose to all fields
SSD= less hot spots
Which of the following can be classified as indirectly ionizing radiaiton? -
answerPhotons
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? - answera 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 - answera small
block over the cord in the inf post corner of both lateral fields
In Photoelectric interactions - answerthe entire energy of the incident photon is
absorbed by the resulting electron
Film badges used for personnel monitoring contain filters that are used to: - answerfitler
info about beam quality and energies
Giving too much radiation to which of the following can lead to xerostomia - answerbase
of tongue
The inguinal lymph nodes are located at a depth of - answer2-18 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 -
answermeasure 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: - answera single 20 MeV
electron field
-^energy ^ surface dose
Mass attenuation coefficient depends on the - answerthickness of the material being
atttenuated
The binding energy of the nucleus - answerrepresents a mass defect in the nucleus
-binding energy of nucleus is proportional to the stability of a nucleus
, Accuracy for radiation therapy tx require accuracy within: - answer+/- 3%
daily output +/- 3%
the value for the Ngas calibration factor for an ioniziation chamber will depend on the: -
answercomposition of the chamber wall
Which are the following descriptors of characteristic x-rays or brems radiation is true? -
answerCharacteristic 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 -
answer3%
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? -
answer0.1x1+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? - answer+/-2
The expected accuracy of tx planning systems that perfrom brachytherapy dose calc's
should be within - answer+/-5%
The number of nuclei decaying per second is expresssed in terms of their? -
answeractivity
Prior to tx h&n pts with IMRT, a 3 field techn was used. Choose the best option to keep
the cord dose under cord tolerance when total rx dose would normally go higher than
50Gy - answerreduce lateral fields post and add an electron beam fields
The adv fo an electron beam over kilovoltage x-ray beam for tx of superficial tumors is -
answerdecrease dose to bone
The five year survival rate for a pancreatic tumor tx with primary radiation is? - answer0-
5%
If the exposure rate constant is 0.87 rcm^2hr^-1mCi^-1 and the average pt transmission
factor is 0.20, the exposure rate at 12.5cm for a pt who has been injected with 20 mCi of
Tc99m is - answerActivity x dose rate/d^2
0.87x.20x20/12.5^2= 0.0223R/hr-22.3mR/hr
