Material selection is a foundational part of embolization coil design, directly influencing how a coil performs under fluoroscopy, how it packs within a vessel, and how the body responds to it long term. INVAMED's Spider coil platform uses a platinum-tungsten (92/8%) alloy, a composition chosen deliberately to balance several competing design priorities. This article explores the rationale behind platinum-tungsten coil design for clinicians evaluating embolic coil options.
Why Platinum as a Base Material?
Platinum has been used in vascular implants for decades due to a well-established biocompatibility profile and a high atomic number, which gives it strong inherent radiopacity. In embolization coils, radiopacity is critical: the physician must be able to see the coil clearly on fluoroscopic imaging throughout the entire deployment process, from initial placement to final packing density assessment.
Pure platinum, however, is a relatively soft metal. In coil applications, softness can affect how well a coil holds its designed secondary shape (the coil-within-a-coil configuration that helps it conform to irregular vessel or aneurysm geometry) once deployed.
Why Add Tungsten to the Alloy?
Tungsten is alloyed with platinum specifically to increase stiffness and mechanical strength without significantly compromising radiopacity. The 92/8% platinum-tungsten ratio used in Spider coils is intended to strike a balance:
- Sufficient softness to allow the coil to conform to vessel or aneurysm wall irregularities
- Sufficient stiffness to help the coil hold its designed shape and resist unwanted straightening under blood flow pressure
- Maintained radiopacity so the alloy remains clearly visible under standard fluoroscopic imaging despite the addition of tungsten
This engineered balance is a key reason platinum-tungsten alloys are widely used across coil embolization platforms in interventional radiology and neurointervention.
How Does Alloy Composition Affect Packing Density?
Coil packing density—the proportion of a vessel or aneurysm volume filled by coil material—is influenced in part by how predictably a coil holds its shape once deployed. A coil that reliably assumes its intended secondary configuration is generally easier for physicians to pack in a controlled, layered fashion, which supports achieving adequate packing density with a reasonable number of coils. Unpredictable coil behavior, by contrast, can complicate packing and may require additional coils or repositioning.
What Other Design Elements Complement the Alloy?
Beyond the base alloy, coil systems like Spider often incorporate synthetic fibers to enhance thrombogenicity, and are engineered with varying softness along their length (sometimes called complex or soft coils) to support different phases of packing, from initial framing coils to final finishing coils. Coil diameter selection—Spider coils range from approximately 2–30 mm—is determined by the treating physician based on vessel or aneurysm sizing from pre-procedural imaging.
Frequently Asked Questions
Why is radiopacity so important in coil material selection?
Radiopacity allows the physician to visualize the coil in real time under fluoroscopy, which is essential for confirming accurate placement and monitoring packing density throughout the procedure.
Does adding tungsten reduce coil biocompatibility?
Platinum-tungsten alloys used in vascular coils are engineered and manufactured to maintain established biocompatibility standards for implantable devices; specific biocompatibility data is detailed in the official IFU.
What is the platinum-tungsten ratio used in Spider coils?
Spider coils use a 92/8% platinum-tungsten alloy composition, balancing radiopacity, biocompatibility, and mechanical strength.
Related INVAMED Resources
- Embolization Products — INVAMED's full embolization device portfolio
- Spider Peripheral Coil System Overview — full system design and application concepts
- Contact INVAMED — request the IFU or technical specifications
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.