SIR-Spheres® Y-90 resin microspheres are a medical device used in Selective Internal Radiation Therapy (SIRT). The microspheres are extremely small resin beads (about one-third the diameter of a hair) which contain radioactive yttrium-90 (Y-90).
The radioactive microspheres are injected into the main artery that supplies liver tumours, and because of their small size and weight, are taken by the blood flow to the small blood vessels surrounding the tumour where they lodge.
Radioactivity is then delivered directly to the tumour cells in order to destroy them.