Editing Embolization (section)

==Agents==
[[Liquid embolic agents]] – Used for AVM, these agents can flow through complex vascular structures so the surgeon does not need to target the catheter to every single vessel.
* [[Butyl cyanoacrylate]] (NBCA) – This material is approved by FDA in 2000 for embolisation of cerebral arteriovenous malformation. When exposed to an environment containing [[anion]]s such as blood or water, it polymerises quickly. Catheters should be flushed with dextrose 5% to prevent premature polymerisation within the catheter. NBCA completely occludes vessels and is permanent. However, the polymerisation can spread distally or proximally of the intended location.<ref>{{cite journal | vauthors = Vaidya S, Tozer KR, Chen J | title = An overview of embolic agents | journal = Seminars in Interventional Radiology | volume = 25 | issue = 3 | pages = 204–215 | date = September 2008 | pmid = 21326511 | pmc = 3036437 | doi = 10.1055/s-0028-1085930 }}</ref>
* [[ethiodol]] – Made from [[iodine]] and [[poppyseed]] oil, this is a highly viscous agent. It is usually used for chemoembolizations, especially for hepatomas, since these tumors absorb iodine. The half life is five days, so it only temporarily embolizes vessels.
* [[EVOH|Ethylene Vinyl Alcohol Copolymer]], soluted in [[Dimethyl sulfoxide|Dimethyl-Sulfoxide]] (DMSO) under the trade name [[Onyx (interventional radiology)|Onyx.]] Depending on the desired character of the liquid, the concentration can be varied: For example, 6% EVOH (trade name Onyx 18) or 8% EVOH (trade name Onyx 34). Micronized [[tantalum]] powder is added in order to maintain [[Radiopacity]].
[[Sclerosing agents]] – These will harden the endothelial lining of vessels. They require more time to react than the liquid embolic agents. Therefore, they cannot be used for large or high-flow vessels.
* [[ethanol]] – This permanent agent is very good for treating AVM. The alcohol does need some time to denature proteins of the endothelium and activate the coagulation system to cause a blood clot. Therefore, some surgeons will use a balloon occlusion catheter to stop the blood flow and allow time for ethanol to work. Ethanol is toxic to the system in large quantities and may cause compartment syndrome. In addition, the injections are painful.
* [[ethanolamine oleate]] – This permanent agent is used for sclerosing [[esophageal varices]]. It contains 2% benzyl alcohol, so it is less painful than ethanol. However it does cause hemolysis and kidney failure in large doses.
* [[sotradecol]] – This agent is used for superficial lower extremity varicose veins. It has been around for a very long time and is a proven remedy. However, it does cause hyperpigmentation of the region in 30% of patients. It is less painful than ethanol.
[[Particulate embolic agents]] – These are only used for precapillary arterioles or small arteries. These are also very good for AVM deep within the body. The disadvantage is that they are not easily targeted in the vessel. None of these are radioopaque, so they are difficult to view with radiologic imaging unless they are soaked in contrast prior to injection.
* ''{{Visible anchor|Gelfoam}} hemostasis'' – It is made of animal-derived gelatin and is shaped into a sponge-like form. It can be made into a paste applied over a surface or made into small particles that can be injected via syringe.<ref name="pmid27936887">{{cite journal |vauthors=Heller HT, Walker BS, Sadow CA, Frates MC |title=Imaging appearance of topical haemostatic agents: pictorial review |journal=The British Journal of Radiology |volume=90 |issue=1070 |pages=20160664 |date=February 2017 |pmid=27936887 |pmc=5685128 |doi=10.1259/bjr.20160664 |url=}}</ref> Gelfoam sheets can be cut into 1–3&nbsp;mm pledgets, mixed with contrast materials for embolization. Gelfoam temporarily occludes blood vessels for 3 to 6 weeks. Each particle sized from 10 to 100 micrometers.<ref name="pmid25247933">{{cite journal |vauthors=Medsinge A, Zajko A, Orons P, Amesur N, Santos E |title=A case-based approach to common embolization agents used in vascular interventional radiology |journal=AJR. American Journal of Roentgenology |volume=203 |issue=4 |pages=699–708 |date=October 2014 |pmid=25247933 |doi=10.2214/AJR.14.12480 |url=}}</ref> Gelfoam use is associated with small risk of infection due to trapped air bubbles.<ref name="pmid25247933"/>
* [[polyvinyl alcohol]] (PVA) – These are permanent agents. They are tiny balls 50–1200&nbsp;um in size. The particles are not meant to mechanically occlude a vessel. Instead they cause an inflammatory reaction. Unfortunately, they have a tendency to clump together since the balls are not perfectly round. The clump can separate a few days later, failing as an embolic agent.
* [[Embolization microspheres]] – These are superior permanent or resorbable particulate embolic agents available in different well-calibrated size ranges for precise occlusion. Embolization microspheres may comprise additional functionality such as [[Targeted drug delivery|drug loading and elution]] capability, specific mechanical properties, [[Medical imaging|imageability]] or [[TheraSphere|radioactivity]]
[[Mechanical occlusion devices]] – These fit in all vessels. They also have the advantage of accuracy of location; they are deployed exactly where the catheter ends.
* coils – These are used for AVF, aneurysms, or [[Physical trauma|trauma]]. They are very good for fast-flowing vessels because they immediately clot the vessel. They are made from [[platinum]] or [[stainless steel]]. They induce clots due to the [[Dacron]] wool tails around the wire. The coil itself will not cause mechanical occlusion. Since it is made of metal, it is easily seen in radiographic images. The disadvantage is that large coils can disrupt the radiographic image. The coil may also lose its shape if the catheter is kinked. Also, there is a small risk of dislodging from the deployed location.
* [[detachable balloon]] – Treats AVF and aneurysms. These balloons are simply implanted in a target vessel, then filled with saline through a one-way valve. The blood stops and endothelium grows around the balloon until the vessel fibroses. The balloon may be hypertonic relative to blood and hence rupture and fail, or it may be hypotonic and shrink, migrating to a new location.