Embolic particles and microspheres are tiny, calibrated materials that physicians can inject through a catheter to block blood flow in a targeted blood vessel. They represent one of several categories of embolic material used in embolization procedures, alongside coils, plugs, and liquid embolic agents. This guide explains what these particles are and how physicians generally use them.
What Exactly Are Embolic Particles?
Embolic particles are small, solid or semi-solid materials manufactured in specific, calibrated size ranges—often measured in micrometers (µm). They are suspended in a liquid carrier and injected through a catheter into the blood vessel supplying a target area, such as a tumor or an area of abnormal bleeding.
Once injected, the particles travel with blood flow until they reach vessels too small for them to pass through, where they lodge and physically block blood flow. Depending on the material, particles may also trigger a localized biological reaction that adds to the occlusion over time.
What Materials Are Embolic Particles Made From?
Several materials are used to manufacture embolic particles and microspheres, including:
- Polyvinyl alcohol (PVA) particles: irregularly shaped particles used in a range of embolization procedures.
- Calibrated microspheres: spherical particles manufactured in precise size ranges, allowing for more predictable vessel-level targeting.
- Drug-eluting or specialty microspheres: particles designed for specific clinical applications where a physician wants embolization confined to a particular size range of vessel.
The specific particle type, size range, and injection technique are all determined by the treating physician based on the target anatomy and clinical objective.
When Are Embolic Particles Used?
Particles are used across a range of embolization procedures, and the specific application always depends on physician evaluation. Broad categories where particles are discussed in interventional practice include:
- Reducing blood flow to fibroids, as in uterine fibroid embolization
- Devascularizing hypervascular tumors before surgery
- Managing certain types of abnormal bleeding
- Selective embolization in organ-specific procedures where distal, small-vessel occlusion is the goal
How Do Particles Differ From Other Embolic Materials?
Compared to coils, which are pre-shaped devices deployed at a specific point, particles are designed to travel further downstream and lodge in smaller vessels, allowing for more distributed, distal occlusion across a vascular bed. Compared to liquid embolic agents, particles are discrete units rather than a continuous flowable cast, which can influence how completely and evenly a target vascular bed is occluded.
The choice between particles, liquid embolics, coils, or a combination is a clinical decision made by the treating physician after reviewing diagnostic imaging.
Frequently Asked Questions
Are embolic particles permanent?
Depending on the material, embolic particles may create a durable, long-lasting vessel occlusion. Whether the effect is intended to be permanent or temporary depends on the specific particle type and clinical goal, and this should be discussed with the treating physician.
Do embolic particles hurt during the procedure?
Embolization procedures are typically performed with sedation or anesthesia as determined by the medical team, and patients may experience some discomfort during or after the procedure. Physicians can discuss what to expect based on the specific procedure being planned.
How do physicians decide on particle size?
Particle size selection depends on the target vessel caliber and the clinical goal—for example, whether the physician wants to occlude larger feeding vessels or achieve more distal, small-vessel embolization. This decision is made by the treating physician based on imaging and procedural planning.
Related INVAMED Resources
- Embolization Products at INVAMED
- LIBRO Non-Adhesive Embolization Agent
- Request Information from INVAMED
Medical Disclaimer: This article is provided for general informational and educational purposes only and does not constitute medical advice, diagnosis, or treatment recommendation. It is not a substitute for consultation with a qualified healthcare professional. Product indications, availability, and regulatory status vary by country. Always refer to the official Instructions for Use (IFU) and consult a licensed physician for guidance specific to your situation. INVAMED devices are intended for use by trained healthcare professionals.