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A patient is to receive 55 Gy to a tumor in the mediastinum. In order to meet the acceptable dose limits for the spinal cord, you could: a. use high energy photon beams to decrease the entrance dose. b. block the spinal cord out of all treatment fields R203,44
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A patient is to receive 55 Gy to a tumor in the mediastinum. In order to meet the acceptable dose limits for the spinal cord, you could: a. use high energy photon beams to decrease the entrance dose. b. block the spinal cord out of all treatment fields
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MDCB
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MDCB
A patient is to receive 55 Gy to a tumor in the mediastinum. In order to meet the acceptable dose limits for the spinal cord, you could:
a. use high energy photon beams to decrease the entrance dose.
b. block the spinal cord out of all treatment fields after 40 Gy is delivered.
c. use a BID t...
a patient is to receive 55 gy to a tumor in the me
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A patient is to receive 55 Gy to a tumor in the mediastinum. In order to meet the acceptable
dose limits for the spinal cord, you could:
a. use high energy photon beams to decrease the entrance dose.
b. block the spinal cord out of all treatment fields after 40 Gy is delivered.
c. use a BID treatment technique to achieve greater repair time for the normal tissue cells.
d. utilize a 3DCRT beam arrangement including oblique beam angles. - ANS d. utilize a
3DCRT beam arrangement including oblique beam angles.
Which of the following statements are true for Iodine-125?
a. half-life 86.4 days.
b. has life-long radiation protection issues.
c. energy of 0.412 MeV.
d. decays exclusively by electron capture. - ANS d. decays exclusively by electron capture.
The most significant effect(s) of an air cavity in a megavoltage beam treatment is:
a. a change in the spectral energy distribution within the cavity.
b. an increased primary photon transmission through the cavity.
c. an enhanced absorption of dose in and beyond the cavity.
d. a partial gain of electronic equilibrium at the cavity interface. - ANS b. an increased
primary photon transmission through the cavity.
For patients with limited life expectancy the common dose fractionation for cord compression is:
a. 800cGy in 1 fraction.
b. 2000cGy in 5 fractions.
c. 3000cGy in 10 fractions.
d. 3750cGy in 15 fractions. - ANS a. 800cGy in 1 fraction.
Mayneord F factor corrects PDD for:
a. heterogeneity.
b. scatter.
c. Inverse square.
d. exponential attenuation. - ANS b. Inverse square- does not correct for scatter
For quality assurance of brachytherapy treatment planning computers, the dose rates should
agree with published data tables to which of the following degrees?
a. +- 1%
, b. +- 2%
c. +- 3%
d. +- 5% - ANS b. +- 2%
The expected accuracy of treatment planning systems that perform brachytherapy dose
calculations should be within: a. +/- 3%
b. +/- 5%
c. +/- 7%
d. +/- 10% - ANS b. +/- 5%
With LINAC based SBRT/SABR and a plan that has a 100% maximum IDL, what is the typical
range of prescription isodose line covering the PTV?
a. 40 - 60 %
b. 60 - 90 %
c. 90 - 100 %
d. > 100 % - ANS c. 90 - 100 %
The ratio of the dose rate of a given field size to the dose rate of the reference field size is:
a. Relative output factor
b. Back scatter factor
c. Percent depth dose
d. Tissue maximum ratio - ANS A. Relative output factor
During which stage of mitosis do the chromosomes align across the equator of the spindle
fibers?
a. prophase
b. metaphase
c. anaphase
d. telophase - ANS b. metaphase
Which of the following is true regarding clinical electron beams?
a. High energy electrons lose energy at a rate of approximately 2 MeV per cm of water or soft
tissue.
b. The depth of the 80% isodose occurs at approximately 1/4 of the electron energy in MeV.
c. The depth of the 90% isodose occurs at approximately 1/3 of the electron energy in MeV.
d. The practical range of electrons (in cm of water) is approximately 2 times the energy in MeV. -
ANS d. The practical range of electrons (in cm of water) is approximately 2 times the
energy in MeV.
What factors are instrumental in determining the dose uniformity in equally weighted parallel
opposed beams?
a. beam energy, tissue inhomogeneity and patient thickness
b. beam energy, patient thickness and tissue maximum ratio
c. beam flatness, patient thickness and collimator scatter
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