Embolization
Embolization refers to the passage and lodging of an embolus within the bloodstream. It may be of natural origin (pathological), in which sense it is also called embolism, for example a pulmonary embolism; or it may be artificially induced (therapeutic), as a hemostatic treatment for bleeding or as a treatment for some types of cancer by deliberately blocking blood vessels to starve the tumor cells. In the cancer management application, the embolus, besides blocking the blood supply to the tumor, also often includes an ingredient to attack the tumor chemically or with irradiation. When it bears a chemotherapy drug , the process is called chemoembolization. Transcatheter arterial chemoembolization (TACE) is the usual form. When the embolus bears a radiopharmaceutical for unsealed source radiotherapy, the process is called radioembolization or selective internal radiation therapy (SIRT). Uses. Embolization involves the selective occlusion of blood vessels by purposely introducing emboli, in other words deliberately blocking a blood vessel. Embolization is used to treat a wide variety of conditions affecting different organs of the human body. Bleeding. The treatment is used to occlude: Growths. The treatment is used to slow or stop blood supply thus reducing the size of the tumour: Malignant hypertension. It  could be useful for managing malignant hypertension due to end stage kidney failure. Technique. First developed by Sadek Hilal in 1968, embolization is a minimally invasive surgical technique. The purpose is to prevent blood flow to an area of the body, which can effectively shrink a tumor or block an aneurysm. The procedure is carried out as an endovascular procedure by an interventional radiologist in an interventional suite. It is common for most patients to have the treatment carried out with little or no sedation, although this depends largely on the organ to be embolized. Patients who undergo cerebral embolization  or portal vein embolization are usually given a general anesthetic. Access to the organ in question is acquired by means of a guidewire and catheter(s). Depending on the organ this can be very difficult and time-consuming. The position of the correct artery or vein supplying the pathology in question is located by digital subtraction angiography (DSA). These images are then used as a map for the radiologist to gain access to the correct vessel by selecting an appropriate catheter and or wire, depending on the 'shape' of the surrounding anatomy. Once in place, the treatment can begin. The artificial  embolus used is usually one of the following: Once the artificial emboli have been successfully introduced, another set of DSA images are taken to confirm a successful deployment. Agents. Liquid embolic agents - Used for AVM, these agents can flow through complex vascular structures so the surgeon does not need to target his catheter to every single vessel. Onyx is an example for a liquid embolic agent. 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. 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. 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.