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Review Questions

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The radiations typically used to image 201Tl are polyenergetic because:

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a. electron capture creates multiple γ-ray emissions.

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b. 201Hg K- and L-shell electrons have different binding energies.

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c. there are multiple γ-ray emissions from 201Hg.

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d. 201Tl γ-ray emissions are more abundant than x rays.

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Answer b. The energy of characteristic x-rays are dependent on the binding energies of the shell from which they originate. Since the K and L shells have different binding energies, so will their respective characteristic x-rays.

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See Chapter 1.

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In the decay of 99mTc, internal conversion is responsible for:

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a. characteristic x rays.

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b. Auger electrons.

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c. β+ emissions.

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d. particulate emissions.

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Answer d. In internal conversion, the energy release from the de-excitation on the nucleus is transferred to an electron. This increase in energy will eject the electron from its shell, resulting in a particulate emission (Internal Conversion Electron).

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See Chapter 1.

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Photons undergoing Compton scatter in tissue:

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a. can be identified by their energy.

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b. are less abundant than the photoelectrons.

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c. are not considered in radiation safety.

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d. are more abundant than Compton electrons.

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Answer a. When a photon undergoes Compton scatter, it loses energy relative to its incident energy, and is therefore identifiable.

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See Chapter 1.

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As the thickness of tissue overlying the heart increases:

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a. the percentage of transmitted photons increases.

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b. the number of photoelectrons decreases.

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c. the amount of characteristic x rays decreases.

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d. the number of energy-degraded photons increases.

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Answer d. As photons travel through tissue, they undergo Compton scatter, which degrades their energy.

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See Chapter 1.

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The international unit for describing dose equivalent is:

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a. Coulomb/kg

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b. Air Kerma

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c. Gray

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