Last revised by Raymond Chieng on 11 Jan 2023

Radiopharmaceuticals are drugs that are bound to radioactive substances.  The pharmaceutically active portion determines the activity that will be measured and the radioactive portion emits radiation that can be measured by the scanner.

A number of radiopharmaceuticals are used in human imaging. They share the physical characteristic of emitting radiation of various kinds. In some cases the emitted particles are detected either directly or indirectly by specialized equipment (e.g. SPECT, PET, gamma camera, etc.) to generate imaging. In other cases, the agent is used to have a tissue effect locally. 

Properties of an ideal radiopharmaceutical:

  • short physical half life time

  • eliminated from the body with an effective half life time approximately equaling the examination time to prevent subsequent exposure to the body

  • pure gamma emitter by isomeric transition

  • gamma rays emitted should be monoenergetic (~150KeV)

  • high specific activity

  • localize largely and quickly at the target site

  • decay into a more stable daughter nucleus

  • easily and effectively attached to the chemical compound at room temperature

  • cheap per patient dose

  • can be easily produced or kept at the hospital site

The radioactivity of radiopharmaceuticals are commonly measured by using miliCurie (mCi) and megaBecquerel (MBq) where 1mCi is equivalent to 37MBq 1.

ADVERTISEMENT: Supporters see fewer/no ads