Isotope notation

Last revised by Ayla Al Kabbani on 2 Aug 2021

When employing formal scientific isotope notation, an isotope is usually expressed in longhand as the name of the chemical element, followed immediately by a dash, and then the mass number (A), i.e. "element-A". When abbreviated, the element's symbol is used, prefixed by a superscripted mass number, above a subscripted atomic number. In everyday practice, the atomic number can usually be omitted, as it is the same for all the isotopes of any one element. 

However, we have decided on Radiopaedia to deviate from standard scientific practice for reasons of simplicity and to not use superscripts for this purpose. 

Instead, we ask that for an isotope of element unobtainium (symbol Un), which has x neutrons, one writes unobtainium-x, and thereafter abbreviate it as Un-x. We ask for the sake of uniformity across the site that you do not write xUn.

Correct usage:

  • fluorine-18, e.g. fluorine-18 FDG PET-CT
  • F-18 e.g. F-18 FDG PET-CT

NB: preferred style for hybrid imaging on Radiopaedia is joining the two modalities by a hyphen "-", not using a "/", a space, or running the two modalities together.

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