Radiation Activity Converter

About the radiation activity converter

Radioactivity describes the rate at which a radioactive substance decays — how many nuclear disintegrations occur per second. The SI unit is the becquerel (Bq), defined as one decay per second. The older unit, the curie (Ci), equals 3.7 × 10¹⁰ Bq, the activity of one gram of radium-226. Medical isotopes are usually labeled in megabecquerels (MBq) or millicuries (mCi); environmental samples in becquerels per kilogram.

Frequently asked questions

• How many becquerels are in 1 curie? +

  Exactly 3.7 × 10¹⁰ Bq, or 37 GBq. So 1 mCi = 37 MBq.

• Is high becquerel always dangerous? +

  Not necessarily. Bq counts decays but not their energy or biological impact. To assess hazard you need absorbed dose (Gy) or equivalent dose (Sv).

• What is a typical activity for nuclear medicine? +

  A diagnostic technetium-99m injection is usually 200–1,100 MBq (5–30 mCi). Therapeutic doses are higher.