Question

Why do you think isotopes of `N` are used in medicine as opposed to other elements with stable isotopes like boron, neon or sodium?

Answer 1

For the same reason that chemists use isotopes to label a particular compound for analysis.

Explanation:

Isotopes, `""^15N`, `""^13C`, are the same chemically as the isotope they replace. They are not the same spectroscopically. Mass spectroscopy would certainly differentiate between the isotopes. In addition, there might be additional spectroscopies that allows the isotope to be interrogated: `""^2H` `NMR` spectroscopy is an example.

The use of `""^10B` in drugs that target cancerous tissue allows neutron capture therapy. The idea is that a `""^10B` laced drug would label a tumour so that it could be selectively targeted by radiation.

So in answer to your question, maybe istopic labelling of boron, or neon, or sodium have not found a useful clinical application.