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Computed Tomography - Radiation Safety questions with answers respectively.
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Computed Tomography - RadiationSafety questions with answers
respectively.
Consider the following dose data from three different CT scans. Which procedure has the highest risk of
acquiring radiation-induced cancer?
A. Procedure 1: Absorbed Dose = 21 mGy, Effective Dose = 11 mSv
B. Procedure 2: Absorbed Dose = 80 mGy, Effective Dose = 3 mSv
C. Procedure 3: Absorbed Dose = 34 mGy, Effective Dose = 10 mSv
D. All risks are equal ANS - A. Procedure 1: Absorbed Dose = 21 mGy, Effective Dose = 11 mSv
Procedure 1 has the highest risk of acquiring radiation-induced cancer. The risk of developing a
radiation-induced cancer is based almost exclusively on the effective dose, therefore, the procedure
with the highest effective dose will usually have the highest risk of developing cancer.
Radiation exposure is calculated with units of:
A. Joules/kilogram (J/kg)
B. Coulombs/kilogram (C/kg)
C. Milligray (mGy)
D. Millisievert (mSv) ANS - B. Coulombs/kilogram (C/kg)
Exposure measures the amount of ionization created in air from x-rays. In the SI system of units and
measures, exposure is represented with units of Coulombs/kilogram (C/kg). The more familiar unit used
in the traditional system for exposure is the Roentgen.
Concerning radiation-induced cancer, increasing the radiation dose to a patient results in:
A. Increased severity of cancer
B. Decreased severity of cancer
C. Increase probability of cancer
,D. Decreases probability of cancer ANS - C. Increase probability of cancer
Increasing radiation dose increases the probability of cancer, but it does not increase the severity of
cancer. A cancer caused by 3 Gray (Gy) of radiation is no worse than a cancer caused by 2 Gy of
radiation. Radiation dose only affects the total probability.
Which two of the following interactions may result in an x-ray photon being emitted out of the patient in
a different direction than the original path? (Select two)
A. Coherent scattering
B. Photoelectric absorption
C. Compton scattering ANS - A. Coherent scattering, & C. Compton scattering
When a photon changes direction as a result of an interaction in an atom, this is called scattering. Both
coherent scattering and Compton scattering cause the photon to change direction when it is emitted out
of the patient. Photoelectric absorption results in total absorption of the photon, so no photon is left
over to be scattered.
The energy of ions created in air from x-ray is called:
A. Exposure
B. Air Kerma
C. Absorbed Dose
D. Equivalent Dose
E. Effective Dose ANS - B. Air Kerma
Air kerma is a measurement defining the energy of ions created in air from radiation, such as x-rays. This
is slightly different from exposure, which measures the total amount of ionization in air.
Which of the following materials will result in the highest x-ray transmission reading?
A. Air
B. Cortical Bone
C. Muscle
, D. Iodine ANS - A. Air
A high transmission reading is the result of a high number of photons passing through the material
without being attenuated. Air does not attenuate much radiation, which would result in a very high
transmission reading.
Which two of the following radiation effects only occur at a specific dose threshold? (Select two)
A. Cataracts
B. Bronchogenic carcinoma
C. Leukemia
D. Skin Erythema ANS - A. Cataracts, & D. Skin Erythema
A radiation effect with a threshold is also called a deterministic effect. Cataracts and skin erythema are
both deterministic effects because they only occur once a specific radiation dose threshold has been
reached. Below this threshold, they do not occur. Leukemia and bronchogenic carcinoma are forms of
cancer and may be caused by any dose of radiation.
Air kerma is measured in units of:
A. Coulombs/kilogram (C/kg)
B. Milligray (my)
C. Millisievert (mSv)
D. Becquerel (Bq) ANS - B. Milligray (my)
KERMA is an acronym which stands for kinetic energy released per unit mass. It is measured in units of
Gray (Gy) or milligray (mGy).
What term describes radiation-induced hair loss?
A. Oligospermia
B. Urticaria
C. Erythema
D. Epilation ANS - D. Epilation
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