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.
In the decay of 99mTc, internal conversion is responsible for:
a. characteristic x rays.
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).
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.
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.
The international unit for describing dose equivalent is: