Background radiation equivalent time

Andrew Murphy et al.

Exposing a patient to radiation is a measured, justified means aiding patient care. Each medical imaging examination utilizing ionizing radiation adheres to the fundamental principles of radiation protection.

The general public's understanding of ionizing radiation is limited 1; this article provides a basic comparison of common medical imaging examinations in contrast to natural background radiation. 

Background radiation is multifactorial, a significant source of background radiation is due to natural radioactivity within geographical structures, this is defined as terrestrial radiation 2. Additionally, large contributions of background radiation arise from cosmic radiation. Background radiation varies throughout the world from 1 to 13 millisieverts (mSv) a year 3.

The following are effective doses of theoretical quantities that were set by the International Commission on Radiation Protection in 2007. They are averages of standard medical imaging examinations in adults and do not pertain to the pediatric population 4,5.

The average background radiation in Australia is 1.5 mSv per year, and this article will use the Australian yearly background radiation as a reference point 3 .

CT examinations

  • head
    • 2 mSv ~1.3 years background radiation 
  • chest
    • 7 mSv ~4.6 years background radiation 
  • chest pulmonary angiogram
    • 10 mSv ~6.6 years background radiation
  • abdomen and pelvis
    • 10 mSv ~6.6 years background radiation
  • coronary angiogram
    • 12 mSv ~8 years background radiation
  • PET
    • 25 mSv ~16.6 years background radiation

Plain radiographic examinations 

  • chest 3
    • 0.1 mSv ~24 days background radiation
  • abdomen
    • 1.2 mSv ~ 292 days background radiation
  • spine
    • 1.5 mSv ~1 year background radiation
  • extremities
    • 0.001 mSv ~6 hours background radiation
Imaging physics

Article information

rID: 53885
Synonyms or Alternate Spellings:
  • BRET (background radiation equivalent time)

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