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SIR-Spheres® Y-90 resin microspheres

About SIRT

Selective internal radiation therapy (SIRT), also known as radioembolization, is a liver-directed therapy and is typically a two-stage process – the work-up and the treatment.

It requires the involvement of a multidisciplinary team consisting of representatives from most, if not all, of the following specialties: Medical Oncology, Surgical Oncology, Gastroenterology / Hepatology, Nuclear Medicine, Interventional Radiology/Oncology, and Radiation Safety.

SIRT targets liver tumors directly with locally applied radiation, while sparing healthy liver tissue, by using the special tumor's blood supply.

Healthy liver tissue derives about two-thirds of its blood from the portal vein, with one-fifth to one-third of the blood coming from the hepatic artery.1

In contrast, liver tumors derive up to 90% of their blood from the hepatic artery, since they need a profuse supply of highly oxygenated blood. The hepatic artery therefore provides an ideal channel for a targeted tumor treatment.

Treatment Goals

  • Increase the time to progression.
  • Extend overall survival.
  • Potentially downsize or downstage tumors for liver resection, ablation or transplantation.
  • Provide palliation of symptoms.


SIR-Spheres® Y-90 resin microspheres are administered under local anesthesia by a specially trained healthcare professional who​:

  • makes a small incision, either into the femoral artery near the groin (A) or the radial artery (A')​.
  • guides a microcatheter to the pre-specified site in the hepatic artery (B) (as identified during the pre-treatment planning).
  • administers SIR-Spheres through this catheter.
SIRT Treatment

1. Lautt WW. Hepatic Circulation: Physiology and Pathophysiology. Morgan & Claypool Life Sciences; 2009.