Food and Drug Administration (FDA)–approved and commercially available radioactive microspheres and describe their differences
SIR-Spheres are nonbiodegradable resin spheres with a median size of 32 μm and are FDA approved for the treatment of unresectable colorectal liver metastases. TheraSphere therapy consists of nonbiodegradable glass spheres with a median size of 25 μm and is FDA approved for the treatment of unresectable HCC ( Figure 68-2 ). The activity per particle is higher with TheraSphere, which measures 2500 Bq as opposed to 50 Bq for SIR-Spheres. The number of particles delivered per treatment and the embolization effect with TheraSphere is less compared with SIR-Spheres.