MCQ in Medical Physics

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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?

1. They can never be thrown away since some activity always remains.
2. They can be thrown away immediately since the amount of activity is generally harmless.
3. They can only be disposed of by a commercial rad-waste service,
4. They can be stored until reaching background levels and then disposed of with other medical trash.
5. 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:

1. Consider all walls as primary barriers.
2. Assign all walls a use factor (U) of 1.
3. Assign all areas adjacent to the installation an occupancy factor (T) of 1.
4. Shield all areas to a radiation level of 100 mrem per week.
5. 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 _____.

1. Does not exist as a free particle.
2. Cat be accelerated by a linac.
3. Demonstrates a Bragg peak.
4. ls best shielded by high-Z materials.
5. 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?

1. Electrons.
2. Protons.
3. Positrons
4. Neutrons
5. Photons.

5. CT or Hounsfield numbers arc linearly related to:

1. Mass density.
2. Electron density.
3. Linear attenuation coefficient
4. Mass absorption coefficient.
5. 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. 1.1cm
2. 1.5cm
3. 1.9cm
4. 2.0cm
5. None of the above

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