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Review Questions

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

a. electron capture creates multiple γ-ray emissions.

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

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

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

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.

See Chapter 1.

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

a. characteristic x rays.

b. Auger electrons.

c. β+ emissions.

d. particulate emissions.

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).

See Chapter 1.

Photons undergoing Compton scatter in tissue:

a. can be identified by their energy.

b. are less abundant than the photoelectrons.

c. are not considered in radiation safety.

d. are more abundant than Compton electrons.

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

See Chapter 1.

As the thickness of tissue overlying the heart increases:

a. the percentage of transmitted photons increases.

b. the number of photoelectrons decreases.

c. the amount of characteristic x rays decreases.

d. the number of energy-degraded photons increases.

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

See Chapter 1.

The international unit for describing dose equivalent is:

a. Coulomb/kg

b. Air Kerma

c. Gray


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