RHS Radiation Safety Practice Questions

What the Radiation Characteristics and Protection domain covers

• Factors in x-ray production: kVp, mA, exposure time and dose
• Radiation characteristics and physics: wavelength, penetration, absorption, primary and scatter radiation
• Radiation biology: cell sensitivity, latent and recovery periods, short- and long-term, somatic and genetic effects
• Units: gray, sievert, roentgen, rem and coulombs per kilogram
• Dose: maximum permissible dose, cumulative occupational dose, and effective, absorbed and equivalent dose
• Operator protection by barrier, position and distance; patient protection under ALARA and ADA/FDA guidelines
• Filtration, shielding, collimation, the PID, beam alignment devices and patient size and age
• Patient concerns, informed consent or refusal, and what to do when the x-ray unit seems to malfunction

This list is our own summary. DANB publishes the full outline, references and acronym list in its RHS Exam Outline and References.

Ideas the questions test most

1. kVp controls energy and contrast; mA and exposure time control the number of x-rays and image density.
2. Doubling the distance from the source cuts intensity to one quarter (inverse square law).
3. Young, rapidly dividing cells such as blood-forming cells are the most radiosensitive; nerve and muscle are the most resistant.
4. 1 gray = 100 rads; 1 sievert = 100 rem; coulombs per kilogram replaced the roentgen.
5. The occupational limit is 50 mSv (5 rem) per year. Stand behind a barrier, or at least 6 feet away at 90 to 135 degrees to the beam.
6. Filtration removes low-energy x-rays; collimation limits beam size; a rectangular PID exposes less tissue than a round one.

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Common questions

Other RHS domains

• Purpose and Technique (50%)
• Infection Prevention and Control (25%)
• DANB RHS practice test