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1. Which of the following is true for low-level radioactive wastes, such as tubing, and swabs contaminated with Tc-99m?
- They can never be thrown away since some activity always remains.
- They can be thrown away immediately since the amount of activity is generally harmless.
- They can only be disposed of by a commercial rad-waste service,
- They can be stored until reaching background levels and then disposed of with other medical trash.
- None of the above.
2. A shielding design for a diagnostic or therapy installation (such as a Cyberknife), when there is no restriction on the beam direction, must:
- Consider all walls as primary barriers.
- Assign all walls a use factor (U) of 1.
- Assign all areas adjacent to the installation an occupancy factor (T) of 1.
- Shield all areas to a radiation level of 100 mrem per week.
- Shield such that adjacent areas will not receive instantaneous dose rates greater than 2 mR/hr
3. Which of the following statements is true? A neutron _____.
- Does not exist as a free particle.
- Cat be accelerated by a linac.
- Demonstrates a Bragg peak.
- ls best shielded by high-Z materials.
- Has a mass approximately equal to the proton mass.
4. Far which of the following particles can one observe a Bragg peak in the depth-dose curve?
- Electrons.
- Protons.
- Positrons
- Neutrons
- Photons.
5. CT or Hounsfield numbers arc linearly related to:
- Mass density.
- Electron density.
- Linear attenuation coefficient
- Mass absorption coefficient.
- Effective atomic number.
6. A patient is treated with 6 MV photon fields of 15 and 30 cm height, respectively, at100 cm SSD. In order to match the fields at 5 cm depth, the gap on skin should be:
- 1.1cm
- 1.5cm
- 1.9cm
- 2.0cm
- None of the above