About SIR-Spheres microspheres

SIR-Spheres microspheres are a medical device used in Selective Internal Radiation Therapy (SIRT) for liver tumours. SIR-Spheres microspheres are a permanent implant and for single use only. The biocompatible resin microspheres containing yttrium-90 have a median diameter of 32.5 microns (range between 20 and 60 microns). Yttrium-90 is a high-energy beta-emitting isotope with no primary gamma emission. The maximum energy of the beta particles is 2.27MeV with a mean of 0.93MeV. The maximum range of emissions in tissue is 11mm with a mean of 2.5mm. The half-life is 64.1 hours. Following administration, 94% of the radiation is delivered in 11 days. These properties of the SIR-Spheres microspheres mean that the microspheres lodge preferentially in the microvasculature surrounding the tumour, maximising tumourcidal effects and minimising the effects on healthy liver parenchyma .