Selective Internal Radiation Therapy using SIR-Spheres® Y-90 resin microspheres enables radiation, which is often used to treat cancer, to be delivered directly into the liver tumors by using the tumor’s own blood supply. Once injected, the microspheres are carried to the small blood vessels of the tumor where they lodge and emit radiation to kill the tumor cells.

SIR-Spheres Y-90 resin microspheres Delivered Using Liver's Unique Blood Supply

The liver is unique by being fed by two blood supplies consisting of the hepatic artery and portal vein.

Normal liver tissues get most of their blood supply from a large blood vessel called the portal vein.

Portal vein
Liver with highlighted portal vein (main blood supply to healthy liver tissue)

Liver tumors however get almost all of their blood supply from the hepatic artery.

Hepatic artery
Liver with highlighted hepatic artery (tumor feeding blood vessel)

Due to the unique blood supply to the liver, the SIR-Spheres Y-90 resin microspheres are injected directly into the hepatic artery so exposure to the remaining healthy liver tissue is minimized.

Spheres injected
SIR-Spheres Y-90 resin microspheres are released into the hepatic artery

SIR-Spheres Y-90 resin microspheres Carried by Blood Flow to Tumor 

Spheres entering tumor
SIR-Spheres Y-90 resin microspheres are delivered in and around the tumor

Once injected, the microspheres are small (1/3 width of a human hair) and light enough to be carried by the blood flow directly within and around the liver tumor.

Human hair comparison
SIR-Spheres Y-90 resin microspheres are 1/3 width of a human hair

Spheres carried by blood flow
SIR-Spheres Y-90 resin microspheres are carried by blood flow

The microspheres, however, are too large to pass through the small blood vessels within the tumor and become permanently trapped within and around the tumor.

SIR-Spheres Y-90 resin microspheres Emit Tumor Killing Radiation

Zoom in on spheres
SIR-Spheres Y-90 resin microspheres emit radiation to kill the tumor

When lodged in the tumor, the microspheres emit radiation that only kills the tumor cells while causing minimal damage to the surrounding tissue.

After the administration of the microspheres to the tumor is complete, the radiation emitted from the microspheres decreases over a two week timeframe and has decayed after one month. The decayed microspheres remain in the liver but are harmless.

Necrosed tumor
SIR-Spheres Y-90 resin microspheres can shrink tumors

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How are SIR-Spheres Y-90 resin microspheres administered?

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