Last revised by Dr Raymond Chieng on 16 Jun 2022

Yttrium-90 (90Y) is a radioisotope; derived from the decay of 90Sr.

Yttrium-90 decays due to the emission of β- particles, with a half-life of 2.67 days 5. It can be used for metabolic radiopharmaceutical therapy, for example: non-Hodgkin B-cell lymphoma radioimmunotherapy (radiopharmaceutical therapy and immunotherapy). The radiopharmaceutical used is 90Y-ibritumomab tiuxetan; it is a murine monoclonal antibody (mAb) directed at human CD20. Radioactive yttrium is bound to the mAb through the tiuxetan, a bifunctional chelator.


Colloidal yttrium-90 citrate is the radiopharmaceutical used in radiosynoviorthesis (RSO), the radionuclide therapy for the treatment of joint inflammation 4.

Chemical-physical characteristics

Yttrium belongs to the group of transition metals; it has atomic number (Z) 39 and atomic weight 88.90585

Its electronic configuration is: [Kr] 4d1 5s2

The maximum energy of the emitted particles is 2.28 MeV with an average path in the human tissuses of approximately 5.8 mm. It decays in the non-radioactive isotope 90Zr.

History and etymology

Yttrium was discovered in 1794 by Johan Gadolin, a Finnish chemist, in a sample of mineral originating from Ytterby (Sweden).

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