Which of the following is not a common embolic agent used in TACE/SIRT?

Transarterial chemoembolization (TACE) and selective internal radiation therapy (SIRT) are interventional procedures used primarily for treatment of liver tumors, where embolic agents are introduced to block blood flow to the tumor while delivering chemotherapy or radioactive substances.

The use of polyvinyl alcohol (PVA) particles, coils, and microspheres is well established in these procedures. PVA particles serve as embolic agents due to their ability to occlude small blood vessels effectively while allowing for drug delivery. Coils are frequently used as a method of occlusion in various vascular interventions, including TACE. Microspheres are specifically designed for liver-directed therapies, either for delivering chemotherapy or as a carrier for radioactive isotopes in SIRT.

In contrast, metal fragments are not typically used as embolic agents in these procedures. While they could theoretically obstruct vessels, their unpredictable nature can lead to complications such as fragment migration or uncontrolled embolization, making them unsuitable for controlled embolic therapy. Thus, the absence of metal fragments in routine TACE or SIRT procedures confirms that they are not a common embolic agent used in these treatments.