Y90 Radioembolization (SIRT) — What is it?

Key Facts at a Glance

2-stage procedure: mapping (Day −14) then treatment (Day 0)
SPECT-CT dosimetry calculated before treatment

What is Y90 radioembolization?

Y90 radioembolization (also called SIRT — Selective Internal Radiation Therapy) uses tiny glass or resin microspheres loaded with the radioactive isotope yttrium-90 to deliver targeted radiation directly to liver tumours via their arterial blood supply.

Unlike external beam radiotherapy, Y90 delivers radiation from inside the tumour — sparing the surrounding liver parenchyma. It combines the effects of embolization (reducing blood supply) and brachytherapy (internal irradiation) in a single procedure. Two products are available: TheraSphere® (glass microspheres, Boston Scientific) and SIR-Spheres® (resin microspheres, Sirtex).

How does the procedure work?

2-stage procedure

Mapping procedure (Day −14)

Angiography + injection of macro-aggregated albumin labelled with Tc-99m (MAA) to simulate Y90 distribution. SPECT-CT 3D imaging calculates the lung shunt fraction and predicts dosimetry. Hepatic arterial anatomy is mapped and optimised.

Y90 treatment (Day 0)

Super-selective arterial catheterisation of tumour-feeding arteries under guidage scanner per-procédure guidance. Y90 microspheres injected. Procedure duration: 1–2 hours. Local anaesthesia. 2–4h post-procedure monitoring. Discharge same day or next morning.

→ Y90 at Cochin AP-HP → TACE → HCC treatment

🇫🇷 French version: y90-radioembolisation-definition.html

Why this page is trustworthy

Written by the Interventional Radiology team at Cochin Hospital AP-HP, Université Paris Cité. Medically reviewed by an interventional radiologist of the department. Last updated: August 2026.

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Y90 Radioembolization (SIRT) — Principles & Indications