MBq

MBq, or megabecquerel, is the SI unit of radioactivity. It denotes the rate at which a material undergoes radioactive decay, with one becquerel equaling one decay per second. Therefore, one megabecquerel is 1,000,000 decays per second.

In relation to other units, 1 MBq equals 1 × 10^6 Bq. For context, 1 becquerel is a very small rate, while the curie (Ci) is a much larger traditional unit: 1 Ci equals 3.7 × 10^10 Bq. Consequently, 1 MBq is about 2.7 × 10^-5 Ci and about 0.027 mCi, which is also roughly 27 μCi.

MBq is commonly used in medicine and research to specify the administered activity of radiopharmaceuticals, such as those used in nuclear medicine imaging (PET and SPECT) and certain radiotherapy modalities. It conveys the number of radioactive decays occurring per second in the administered material, but it is not a direct measure of dose absorbed by tissue; dose depends on decay rate, radiopharmaceutical distribution, and patient-specific factors.

Measurement and calibration are typically performed with dose calibrators and counters calibrated for specific isotopes. Activity values in MBq guide procedural planning, imaging timing, and safety considerations, including shielding, handling, and patient exposure.

See also: Becquerel, Curie, radiopharmaceutical, radiotracer, nuclear medicine, PET, SPECT.