RHS: Radiation Characteristics and Protection practice questions

Answer: D) Been deflected from its path

• AIncorrect. It still carries energy.
• BIncorrect. That's primary radiation.
• CIncorrect. That's leakage radiation.
• DCorrect. After interacting with matter.

Answer: A) Take the unit out of service and report it so a qualified technician can inspect it before reuse

If an x-ray unit may be malfunctioning, stop using it and report it so a qualified person can inspect it. Workarounds such as increasing distance, restarting the unit, or waiting for the routine survey still put people at risk of unnecessary exposure.

• ACorrect. A unit that may be producing unintended radiation should not be used until a qualified person has inspected it and confirmed it is safe. Reporting damaged equipment through the office's procedure is part of the safety protocol.
• BIncorrect. Distance protects the operator, but it does nothing about uncontrolled exposure to the patient. A possibly malfunctioning unit should not be used at all until it has been inspected.
• CIncorrect. Power-cycling does not show that the timer or exposure circuit works properly. Testing it by exposing patients would put them at needless risk.
• DIncorrect. Routine surveys by a qualified expert happen at long intervals (about every four years). A suspected malfunction has to be dealt with right away, not deferred.

Answer: D) Based on each patient's individual needs and risk

• AIncorrect. Needs vary.
• BIncorrect. Selection is individualized.
• CIncorrect. The dentist decides based on need.
• DCorrect. They aren't routine on a fixed schedule for all.

Answer: A) It restricts the beam to roughly the size and shape of the receptor, so less tissue is exposed

Rectangular collimation shapes the beam to closely match the receptor, so much less tissue is irradiated. FDA/ADA guidance cites up to a fivefold dose reduction compared with round collimation.

• ACorrect. A rectangular beam that closely matches the receptor exposes much less of the patient's tissue. FDA/ADA guidance says it can lower dose by up to fivefold compared with round collimation.
• BIncorrect. This describes aluminum filtration, which reduces dose by absorbing low-energy photons. Collimation changes the size and shape of the beam, not its energy.
• CIncorrect. This describes a longer PID. A rectangular collimator lowers dose by limiting the beam's area, not by changing the distance.
• DIncorrect. The collimator sits at the tube end and shapes the primary beam before it reaches the patient. Less scatter is a side effect of the smaller beam, not how the collimator works.

Answer: B) Using fast receptors with rectangular collimation

• AIncorrect. That raises dose.
• BCorrect. Both reduce exposure.
• CIncorrect. Retakes add dose.
• DIncorrect. That affects the operator.

Answer: D) Higher energy

• AIncorrect. Shorter wavelength means higher energy.
• BIncorrect. Shorter wavelength means higher energy.
• CIncorrect. They penetrate more.
• DCorrect. And greater penetrating power.

Answer: B) Material thickness that halves beam intensity

• AIncorrect. It describes beam penetration.
• BCorrect. It describes beam quality.
• CIncorrect. It's about attenuation.
• DIncorrect. That isn't the definition.

Answer: A) It records the wearer's occupational radiation exposure and is worn only while working

A personnel dosimeter is a passive badge that records the wearer's occupational radiation exposure. It is worn only at work, not during personal x-rays, and does not replace protective measures.

• ACorrect. A personnel dosimeter is a passive monitor of the radiation the employee receives on the job. It is worn at work only, so it reflects occupational exposure.
• BIncorrect. The badge monitors the staff member who wears it, not the patient. Clipping it near the tube head would not measure the wearer's own exposure.
• CIncorrect. The badge tracks only occupational exposure. Wearing it during personal medical or dental x-rays would distort the occupational record.
• DIncorrect. A standard badge is passive and is read after the wearing period, not in real time. It never replaces the use of distance, barriers, or shielding.

Answer: C) About 60 to 90 kVp

• AIncorrect. That's too high.
• BIncorrect. That's too low.
• CCorrect. It controls penetrating power.
• DIncorrect. That's far too high.

Answer: B) About 2.75 inches (7 cm)

• AIncorrect. That's far too large.
• BCorrect. Rectangular collimation is even smaller.
• CIncorrect. That's too small for imaging.
• DIncorrect. Limits apply.