Radiation Safety Key Points

Ionizing Radiation and Its Effects

  • Ionizing radiation has enough energy to change the chemical composition of matter by liberating electrons from atoms or molecules.

  • Non-ionizing radiation has less energy but can still excite molecules and atoms, causing them to vibrate faster.

X-ray Production/Exposure Factors

  • Electrical current (7-10mA) is applied to the cathode, emitting electrons which affect image density.

  • Voltage (50-90kVp) accelerates electrons to hit the tungsten target on the anode, influencing density and contrast.

  • Exposure time affects the number of photons and the image density.

  • Density/contrast are essential for high diagnostic value.

Exposure to Ionizing Radiation

  • Natural background radiation: solar, cosmic, rocks, earth, radon gas.

  • Artificial radiation: waste, fallout, microwaves, appliances, communication.

  • Medical exposure: diagnostic, therapeutic.

  • Occupational exposure: health, industrial, researcher, pilot, miners.

Biological Effects of Ionizing Radiation

Deterministic:

  • Caused by cell death; effects occur only above a dose threshold.

  • Severity is proportional to dose; not from diagnostic radiology doses.

  • Examples: radiation-induced skin burns.

Stochastic:

  • Caused by sub-lethal DNA damage; no minimum threshold dose.

  • Higher doses increase risk; some tissues are more sensitive.

  • Examples: cancer, heritable effects.

Radiation Safety/Protection

  • Guiding principles: Justification, Optimization, Dose limitation.

Justification:

  • Diagnostic benefit should outweigh harm risk.

Optimization (ALARA - As Low As Reasonably Achievable):

  • Minimize exposure; ensure equipment maintenance; reduce technical errors; use collimation; provide training; use correct factors and processing methods. Prevent need for retakes.

Dose Limitation:

  • Prevent unacceptably high doses to patients, staff, and the public.

  • Distance: remain >2m from x-ray tube.

  • Position: use barriers/shields.

Dose

  • Absorbed dose: Energy imparted to mass; unit is Gray (Gy).

  • Equivalent dose: Absorbed dose multiplied by a radiation weighting factor; unit is Sievert (Sv).

    • For X-rays, 1 Gy = 1 Sv.

  • Effective dose: Equivalent dose multiplied by tissue weighting factor; unit is Sievert (Sv).

Effective Dose Comparison

  • Bitewings: 0.0025-0.005 mSv.

  • Panoramic: 0.02 mSv.

  • CBCT (small FOV): 0.05 mSv.

Risk Considerations

  • Background radiation in Australia: 1.5 mSv/year.

  • Return flight Melbourne to London: 0.11 mSv.

Legislation in South Australia

  • Governed by Radiation Protection and Control Regulations 2022.

Duties of Owners

  • Register equipment, ensure safety, maintain equipment, provide monitoring, training, safety manual.

Duties of Operators

  • Must be licensed and comply with regulations.

  • Students: All exposures must be authorized and supervised.

Who Can Hold a Radiation License?

  • BDS: All intra-oral radiographs, panoramic radiographs, lateral cephs.

  • BOH: All intra-oral radiographs, can take panoramics (not CBCT), but Can NOT authorize/prescribe/diagnose panoramics/CBCT

Informed Consent

  • Provide individualized information, address concerns truthfully, avoid jargon, document consent.