Transarterial radioembolization (TARE), which delivers radioactive microspheres directly into liver tumors through their blood supply, depends on a carefully controlled vascular pathway to work safely and effectively. Before the radioactive treatment itself is ever administered, interventional radiologists frequently perform a preparatory mapping and embolization procedure specifically to redistribute hepatic blood flow — closing off vessels that could carry treatment particles to unintended locations. This flow redistribution step, using plugs and coils, is a critical safety layer underlying successful TARE.
Why Is Flow Redistribution Necessary Before TARE?
The liver's arterial supply is not a simple, isolated system — small branch vessels can connect the hepatic arterial tree to nearby organs such as the stomach, duodenum, pancreas, and gallbladder, or to the lungs through microscopic shunting within the liver itself. If radioactive microspheres intended for a liver tumor were to travel through one of these connections during TARE, they could deposit radiation in non-target tissue, with potential for injury to organs never intended to receive treatment. Flow redistribution embolization is performed in advance specifically to close off these problematic vessels before the radioembolization treatment is administered.
What Vessels Are Typically Targeted During This Mapping Procedure?
During the preparatory angiography and mapping procedure, the interventional radiologist identifies extrahepatic vessels — branches that normally supply non-liver structures but that arise near or from the hepatic arterial tree — which could inadvertently carry treatment particles away from the liver. Common vessels addressed in this step include the gastroduodenal artery and the right gastric artery, among others depending on individual anatomy. Coils or, in some cases, vascular plugs are used to permanently occlude these vessels, redirecting blood flow more exclusively toward the liver and, specifically, toward the tumor-bearing segments intended for treatment.
How Do Plugs and Coils Each Contribute to This Goal?
Coils are frequently used for this application because the vessels being targeted for redistribution — such as the gastroduodenal artery — are often of a size and length well suited to coil packing, and the precision offered by detachable coil systems supports accurate placement in close proximity to other important branch vessels. Vascular plugs may be selected in some cases where a single-device, defined-length occlusion is preferred for a particular vessel segment. The combination of devices used depends on the specific anatomy mapped during the preparatory procedure.
How Does This Preparatory Step Relate to Dosimetry Planning?
Flow redistribution is typically performed in the same session as, or in close coordination with, a diagnostic step involving a small test dose of a radioactive tracer, which helps the treating team calculate an estimate of lung shunting and plan the therapeutic radioembolization dose. Ensuring that extrahepatic vessels are properly occluded before this mapping step helps make the resulting flow pattern more representative of what will occur during the actual treatment, supporting more accurate planning.
What Happens if Flow Redistribution Is Incomplete or a Vessel Reopens?
In some cases, a vessel that was believed to be adequately occluded during the mapping procedure may recanalize or a previously unidentified branch may become apparent by the time of actual treatment delivery, which is why many treating teams repeat angiographic assessment immediately before administering the radioembolization dose itself, even after a prior mapping and embolization session. This layered, verification-based approach reflects the priority placed on non-target protection throughout the TARE preparation process.
Devices Supporting TARE Preparation
Flow redistribution embolization requires devices capable of durable, precise occlusion of variable-sized extrahepatic branch vessels during TARE preparation. INVAMED manufactures the MultiBEAM Embolization Plug, with manufacturer-reported indications that include TARE preparation, alongside coil-based options for vessels better suited to packed occlusion. Further details are available on the MultiBEAM Embolization Plug product page. Availability and indications vary by country, and the Instructions for Use (IFU) should always be consulted.
Device availability and regulatory status vary by country. Please contact INVAMED or your authorized local distributor for current regulatory information applicable to your region.