MINIMIZING RADIATION EXPOSURE

 

Know where the radiation is & where it is coming from.

Very little radiation comes directly from the x-ray source – outside of the collimated primary beam – since the x-ray tube is surrounded by lead shielding. Therefore, most radiation you will receive will be x-rays scattered from the patient (unless you place yourself within the direct primary beam from the x-ray tube).

• Scattered x-rays from the patient are most intense on the radiation entrance side of the patient.
• Very important The amount of scatter produced is proportional to the collimated area. Reduce the collimation to reduce the scatter!

Keep your hands out of the primary beam

• If your hands might intrude into the primary beam, then wear lead gloves.
• The primary beam in fluoroscopy may be larger than what you see on the image monitor.
• For example, with GE fluoros the radiation field fills the square around the circle that is imaged – there is no iris (circular) collimation. Also, if a fluoro machine is malfunctioning, and has not been tested for proper collimation, the actual radiation field may be MUCH larger than the imaged field. I have seen radiation fields as much as 8 times the size of the imaged field – which were then quickly repaired.

Distance

• Radiation intensity decreases as the distance squared. If the dose rate at 1 meter is 16 mrem/min, then the dose rate at 4 meters is only 1 mrem/min.
• If you must be in the patient room when the x-rays are activated, step away from the patient as much as possible.

Time

• The dose increases as the amount of time you are exposed to the radiation increases.
• Minimize the amount of time that you are in the patient room when the x-rays are activated. Minimize the amount of time the patient is exposed to x-rays.

Shielding

• Your dose is reduced by placing an attenuating material between you and the source of x-rays.
• Shielding can involve placing another person between you and the source of scattered radiation.
• Personal Shielding Items:
  • Lead Apron
  • Thyroid Shield
  • Lead Gloves
  • Leaded Glasses
    The above normally have 0.5 mm lead equivalent which allows approximately a 2% transmittance of incident radiation.
• Equipment and Room Shielding:
  • Lead shielding drapes on x-ray equipment or
  • mounted on arm to ceiling
  • Portable radiation shields (on wheels)
  • Leaded glass windows
  • Leaded walls