Va s c u l a r a n d I n t e r ve n t i o n a l R a d i o l o g y • R ev i ew Medsinge et al. Embolization Agents

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Vascular and Interventional Radiology Review

Avinash Medsinge1 Albert Zajko Philip Orons Nikhil Amesur Ernesto Santos Medsinge A, Zajko A, Orons P, Amesur N, Santos E

A Case-Based Approach to Common Embolization Agents Used in Vascular Interventional Radiology OBJECTIVE. The objective of this article is to familiarize the reader with the most commonly used embolic agents in interventional radiology and discuss an approach for selecting among the different embolic agents. This article reviews their properties and uses a casebased approach to explain how to select one. CONCLUSION. A wide variety of embolic agents are available. Familiarity with the available embolic agents and selection of the most appropriate embolic agent is critical in interventional radiology to achieve optimum therapeutic response and avoid undesired, potentially disastrous complications such as nontarget embolization.

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Keywords: bleeding, embolic agents, interventional radiology, occlusion DOI:10.2214/AJR.14.12480 Received December 29, 2013; accepted after revision April 21, 2014. 1

All authors: Department of Diagnostic Radiology, Division of Interventional Radiology, University of Pittsburgh Medical Center, 200 Lothrop St, Pittsburgh, PA 15213. Address correspondence to A. Medsinge ([email protected]).

This article is available for credit. AJR 2014; 203:699–708 0361–803X/14/2034–699 © American Roentgen Ray Society

ercutaneous transcatheter embolization is a well-established and commonly performed minimally invasive therapeutic option used for a variety of clinical conditions. The goal of embolization is to occlude or decrease blood or lymph flow in arteries, veins, or lymphatic ducts. Since the introduction of autologous blood clot use in the 1970s [1], many sophisticated embolic agents, in conjunction with advancements in imaging and catheter technology, have been developed and shown to be of value in interventional radiology. Each embolic agent has unique characteristics that make it desirable in certain clinical situations and less useful in others; no single embolic agent is suitable for all indications. A thorough knowledge of the properties of each embolic agent and training in its use is required to ensure safe, effective embolization and avoid potential complications. Embolization procedures should be performed only by a well-trained and experienced physician. Complications from nontarget vessel embolization can be disastrous, so attention to detail and selection of the proper agent are paramount [2]. This article describes the commonly used embolic agents in interventional radiology and uses a casebased approach to explain how to select one. Embolic agents can be classified on the basis of their physical state (solid vs liquid), mechanism of action (mechanical vs chemical), and origin (autologous vs biosynthetic or synthetic). In clinical practice, a more use-

ful way of classification is based on the duration of occlusion (Table 1). Temporary Embolic Agents The breakdown of temporary embolic agents leads to recanalization of the embolized vessels within hours (autologous blood clot) to weeks (gelatin sponge). Autologous blood clot—even when modified by adding thrombin and aminocaproic acid—has a rapid lysis time and is rarely used [1]. Gelatin Sponge Gelatin sponge (Gelfoam, Pharmacia & Upjohn), the most widely used temporary embolic agent, is an absorbable bioprosthetic material available as a block (sponge or sheet) or as a powder. Gelfoam provides vessel occlusion typically lasting 3–6 weeks. Gelfoam powder particles range from 10 to 100 μ. These very small particles produce occlusion at the arteriolar level and may lead to severe ischemia. Because of potential tissue infarction, Gelfoam powder is rarely used. Gelfoam sponge is relatively inexpensive, widely available, and easily modified to the size of the target artery. Gelfoam sheets can be cut into pledgets of desired size (usually 1–3 mm) and mixed with contrast material. A detailed description of how to prepare Gelfoam slurry for embolization has been previously reported [3]. For occlusion of large vessels, Gelfoam “torpedoes” can be prepared by tightly rolling small Gelfoam strips and loading them into a syringe nozzle [1]. These torpedoes can also

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Medsinge et al. TABLE 1: Classification of Embolic Agents Based on Duration of Action Duration of Action Temporary

Embolic Agents Gelatin sponge (Gelfoam, Pharmacia & Upjohn), oxidized cellulose, microfibrillar collagen

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Permanent Nonabsorbable microparticles

PVA, TAGMs

Mechanical agents

Coils (pushable, injectable, detachable), detachable plugs

Liquid agents Sclerosants

Ethanol, sodium tetradecyl sulfate

Polymers

NBCA glue, ethylene vinyl alcohol (Onyx, Micro Therapeutics)

Note—PVA = polyvinyl alcohol, TAGMs = tris-acryl gelatin microspheres, NBCA = N-butyl cyanoacrylate.

be used through an existing sheath for embolizing needle or catheter tracts after procedures such as portal vein embolization or liver or lung biopsy in patients with a high risk of bleeding. For arterial occlusion, a Gelfoam slurry can be prepared by macerating the pledgets soaked in contrast material with two syringes and intervening stopcock. Gelfoam use is associated with a small risk of infection due to trapped air bubbles [2, 3]. Oxidized Cellulose and Microfibrillar Collagen Oxidized cellulose and microfibrillar collagen, the other two commercially available temporary embolic agents, are rarely used because they are more difficult to prepare and administer and offer no clinical advantage over Gelfoam. Temporary embolization using Gelfoam is desirable in patients with postpartum hemorrhage or in patients with traumatic pelvic fracture when there are multiple small bleeding sites from different internal iliac artery branches [4, 5]. Gelfoam can also be used if the bleeding iliac arterial branch cannot be selectively catheterized. Temporary embolization is also preferable for treating bleeding due to gastric or duodenal ulcerations that can be managed medically after embolization [6]. Permanent Embolic Agents Most modern embolic agents produce permanent vessel occlusion and can be classified as nonabsorbable microparticles (polyvinyl alcohol [PVA], tris-acryl gelatin microspheres), mechanical agents (coils, detachable plugs), and liquid agents (sclerosant, ethanol, polymers, N-butyl cyanoacrylate [NBCA] glue, ethylene vinyl alcohol [Onyx, Micro Therapeutics]). Nonabsorbable Microparticles Polyvinyl alcohol particles—PVA particles are derived from plastic sponge and are

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available in a wide range of diameters from 45 to 1200 µ. Microscopically the particles are irregular in shape and lodge in the smallest vessel into which they fit. They produce permanent occlusion by adhering to the vessel wall and causing an inflammatory reaction and vessel fibrosis [3]. The major disadvantage with PVA particles is their tendency to aggregate and clump together, which can occur in a vessel more proximal than intended; the catheter itself, leading to clogging of the catheter; and the catheter hub, which can lead to nontarget embolization while the catheter is being flushed [3]. Theoretically, clumping of PVA particles can be avoided by proper suspension, dilution, slow infusion, and resuspension just before injection. PVA particles are now also available as calibrated microspheres (Contour SE, Boston Scientific). Theoretically, calibrated microspheres should overcome the disadvantages of noncalibrated microspheres [4]. Bead Block (Terumo) is a biocompatible deformable PVA hydrogel tinted with reactive blue 4 [7]. It is deformable up to 30% of its original diameter [7]. PVA particles are predominately used for embolization in patients with tumors and uterine fibroids [1, 8] and in those with hemoptysis from chronic inflammatory disease [9]. Drug-eluting beads are capable of loading and releasing chemotherapeutic agents such as doxorubicin or irinotecan in a controlled manner to the tumor when used in transarterial chemoembolization (DC Bead, Biocompatibles UK). These embolic beads are made up of sulfonated PVA microspheres that are soaked with the chemotherapeutic agent before use. Drug-eluting beads loaded with doxorubicin have been used for transarterial chemoembolization of hepatocellular carcinoma for long-term local release of doxorubicin within the tumor [10, 11].

Tris-acryl gelatin microspheres—Trisacryl gelatin microspheres (TAGMs) (Embospheres, Biosphere Medical) are precisely calibrated spherical acrylic copolymer beads cross-linked with gelatin [12]. They are available in six sizes ranging from 40 to 1200 µ. Embospheres are packaged in a 20mL syringe with 1 or 2 mL of Embospheres in saline. An equal amount of undiluted contrast material—which will result in a solution composed of 50% Embospheres-saline mixture and 50% contrast material—is added before use. The hydrophilic nature of the Embospheres prevents aggregation and provides more predictable occlusion than PVA [13]. The size of the microspheres selected should generally be larger than PVA particles in any similar clinical situation [13] because TAGMs will not occlude vessels that are larger than their diameter given that they are less likely to clump within the vessel; hence, embolization may be stopped before stasis occurs in the feeding artery. In addition, the inherent elasticity of TAGMs allows temporary deformation during delivery through a catheter. The indications for microsphere use are the same as for PVA use. The potential drawbacks of TAGMs include the need for intermittent agitation to keep particles in suspension and allergic potential of porcine gelatin content. Embozene microspheres (CeloNova Biosciences) are made of a hydrogel core (polymethylmethacrylate) coated with a shell (Polyzene-F, Embozene, CeloNova Biosciences) [14]. The important feature of Embozene is the precise calibration of the particles, resulting in the tightest size distribution, as compared with a large range of particle sizes (typical range = 200 µ) for Embospheres. Embozene is being used in clinical trials for uterine fibroid embolization (at the time this article was written). Animal studies have shown that Embozene particles

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Embolization Agents have substantial and variable deformation in tissues, which results in a more distal embolization compared to Embospheres [14]. Imageable beads are under investigation and are being tested in animals. For example, PVA hydrogel microspheres loaded with ethiodized oil (Ethiodol, Guerbet) to make them visible at fluoroscopy or on CT are being studied. The use of imageable beads during a transcatheter embolization procedure could allow the operator to see the true spatial distribution of embolic material inside the tissues [15]. Yttrium-90, a pure beta emitter, is a 20- to 60-µ microsphere used in radioembolization of hepatocellular carcinoma and metastatic liver disease. Yttrium-90 is either directly bound to the resin (SIR-Spheres, Sirtex Medical) or an integral part of the glass (TheraSphere, MDS Nordian). The embolization achieved with these microspheres, also carriers of 90Y, results in microvascular occlusion in the tumor [16, 17]. Mechanical Embolic Agents Embolization coils are manufactured in many configurations and sizes and produce permanent vessel occlusion similar to surgical ligation. Coils are generally made from either stainless steel or platinum. Steel coils are less expensive and have greater radial force, which makes them less likely to spontaneously migrate in high-flow situations. Platinum coils are more malleable and are highly radiopaque but are expensive. The most commonly used coil profile includes 0.035- or 0.038-inch and 0.018-inch microcoils. Coils are available in lengths from 1 to 300 mm and diameters from 1 to 27 mm. Coils can be straight, helical, spiral, and complex 3D shapes. Bare metal coils may cause incomplete vessel occlusion because they rely solely on mechanical obstruction. Coils are made more thrombogenic by coating them with polyester fibers (Dacron, DuPont), nylon fibers, or silk fibers (Fig. 1A). Effective vascular occlusion by coils depends on the patient’s ability to form thrombus; therefore, coagulopathic states can hamper effective embolization. Selecting the correct size of coil is critical to form a tightly packed nest and cause crosssectional occlusion. Coils should, in general, be 20–30% larger than the target vessel. However, too much oversizing may result in the coil not being able to form completely in the vessel, resulting in catheter displacement and incomplete vascular occlusion with

a subsequent decrease in coil effectiveness. Undersized coils may be prone to distal migration or nontarget vessel embolization. Embolization coils can be delivered to the desired site by pushing, using a saline flush, or using dedicated detachment systems or coil pushers. Pushable coils and injectable coils— These coils are the most commonly used coils in interventional radiology. They are user-friendly, quickly deployed, and relatively inexpensive. The major disadvantage is their inability to be quickly retrieved once they are extruded from the catheter tip. The coils are loaded into the catheter and delivered to the desired site either by a coil pusher wire or by saline flush using a 1- to 3-mL syringe. Although injecting coils into position with a forceful flush is expedient, coils can be placed more accurately and predictably with a coil pusher. It is recommended that the size of the coil pusher closely match the inner diameter of the catheter to prevent the possibility of wedging the pusher between the coil and the catheter lumen. In addition, when coils are being placed for the treatment of bleeding, a forceful saline flush to deploy a coil could potentially dislodge thrombus formed around a bleeding site. Liquid coils (Berenstein Liquid Coils, Boston Scientific) are a special form of pushable coil. These coils are extremely soft, nonfibered platinum coils (diameter = 0.008–0.016 inch) that can negotiate tight bends and tortuous vessels and conform to the space into which they are injected. These coils can be cut and customized to the anatomy of the patient and can be retrieved by suction with a 20-mL syringe before complete delivery. These coils produce tight compaction and can be delivered distal to the catheter tip if desired [18]. Detachable coils—Detachable coils can be recaptured and repositioned several times before release, which allows more precise placement. These coils are most useful in intracranial interventions or when high vascular flow increases the risk of coil migration and are generally not necessary for peripheral interventions [2, 19, 20]. A variety of controlled release mechanisms exist including mechanical, hydrostatic, or electrolytic. The major disadvantages of detachable coils are their longer procedure time and higher cost. Hydrogel coils are a special type of platinum coils coated with expandable polymer that causes the coil to swell to 9 times its original diameter when exposed to physiologic condi-

tions [21]. Hydrogel coils are available as detachable as well as pushable ones. Care must be taken to ensure these coils do not become lodged within the catheter. Amplatzer vascular plugs—The Amplatzer Vascular Plug (AVP) (St. Jude Medical) is a permanent mechanical embolic device constructed of self-expanding nitinol mesh (Fig. 1B). AVPs are safe and effective embolization devices that are especially suited for precise deployment in high-flow relatively straight vessels when there is possibility of coil migration [22, 23]. The Amplatzer Vascular Plug II (St. Jude Medical) is available in diameters of 3–22 cm and lengths of 6–18 cm. Like detachable coils, AVPs can be recaptured and repositioned for precise deployment. AVPs need to be oversized by 30–50% of the vessel diameter and may require distal placement of a 5- to 8-French guiding catheter, which may be technically challenging in tortuous vessels [24]. The newer smallerprofile Amplatzer Vascular Plug 4 (St. Jude Medical) devices can be deployed through a 0.038-inch 5- to 6-French diagnostic catheter but are currently available only in diameters of 4–8 mm. AVPs are relatively expensive but can significantly reduce procedure time [24]. However, AVPs are nonfibered, and successful embolization with AVPs depends on the patient’s ability to form thrombus for complete occlusion, which can be a limitation in patients with severe coagulopathy. It may take up to 15 minutes for complete thrombosis to occur [24]. AVPs have been used in pulmonary arteriovenous malformations (AVMs), the splenic artery, the portal vein, and persistent varices after transjugular intrahepatic portosystemic shunt (TIPS) placement and for the occlusion of the internal iliac artery before aortoiliac stent-grafting [24]. Liquid Embolic Agents Interest in using liquid embolic agents in peripheral interventions is growing. However, during administration, liquid embolic agents are difficult to control; hence, the administration of these agents demands more experienced operators. Liquid embolic agents do not depend on the patient’s coagulation system for complete occlusion and thus can be effective even in patients with severe coagulopathy. Also, when a bleeding site cannot be reached with a catheter, liquid agents can provide embolization distal to the catheter tip. Absolute alcohol (ethanol) —Ethanol is the most commonly used sclerosant and

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Medsinge et al. causes protein denaturation, which leads to endothelial damage and permanent vascular occlusion [1, 3]. Inadvertent introduction of alcohol into a normal vascular territory can result in serious complications. Latex occlusion balloon catheters are often used to control the flow of ethanol, prevent reflux of ethanol, and keep ethanol in place for a few minutes, allowing the ethanol to interact with the endothelium. Peripheral indications for ethanol use include renal tumor ablation [25] and portal vein embolization before partial hepatectomy [26]. Sodium tetradecyl sulfate—Sodium tetradecyl sulfate, another sclerosant, is an ionic detergent that is used in the treatment of pelvic congestion syndrome [27], varicocele [28], and venous malformations [29]. N-butyl-2-cyanoacrylate—N-butyl-2-cyanoacrylate (NBCA), also commonly known as “glue,” is a clear free-flowing radiolucent liquid. It polymerizes rapidly on contact with ionic solutions such as blood or normal saline and forms a cast of the vessel. Therefore, before the injection of NBCA, the catheter must be flushed with a nonionic solution of 5% dextrose in water. After NBCA is injected, the catheter must be retracted immediately to avoid adherence to the vessel wall. Because the catheter is removed after each injection, a coaxial system is required. Polymerization can be retarded by adding ethiodized oil (Ethiodol) in proportion of 1:1–1:4 depending on the rate of blood flow in the vessel being treated. Ethiodol also contributes to the radiopacity of the mixture. The exact volume required to achieve adequate occlusion is calculated by the initial contrast injection. When using NBCA, it is critical to avoid reflux and nontarget embolization. NBCA can destroy polycarbonate, so special polypropylene syringes are used. Although NBCA is used primarily for the treatment of high-flow AVMs, its use for other applications is growing rapidly [30]. Ethylene vinyl alcohol copolymer—Ethylene vinyl alcohol copolymer (Onyx) is a biocompatible nonadhesive liquid embolic agent with prolonged polymerization time. It is used in patients with peripheral vascular malformations and in those with pseudoaneurysms [31]. Algorithm for Selection of an Embolic Agent Selection of a particular embolic agent [32, 33] depends on the following factors: vessel size, the duration of occlusion desired, the need for tissue viability, and the patient’s clinical condition.

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TABLE 2: Basic Differences Between Proximal and Distal Splenic Artery ­Embolization (SAE) Difference

Proximal SAE

Distal or Superselective SAE

Complications (splenic infarcts, abscess)

Fewer

More

Procedure time

Short

Relatively longer

Radiation exposure

Less

More

Vessel Size Large vessels, such as the feeding artery in a pulmonary AVM or a splenic artery, typically require large coils or AVPs for permanent occlusion. For embolization of small vessels for indications such as bleeding from gastric erosions when the bleeding artery is not angiographically visualized or tumors, particulate embolic agents are most suitable. Duration of Occlusion Desired Temporary occlusion of vessels that lasts for days to weeks is desired in situations such as diffuse posttraumatic pelvic bleeding. Gelfoam is the most popular and widely used temporary embolic agent. Most other embolic agents are permanent. Tissue Viability With the exception of tumor or solid organ ablation, maintenance of issue viability is usually desired. Most organs have some degree of dual vascular or collateral supply that allows safe embolization with permanent devices such as coils, AVPs, or large particles (≥ 300 µ). Tissue infarction is generally desired in tumor embolization. The use of small particles (< 300 µ) results in occlusion distal to potential collateral pathways and may lead to tissue death. Sclerosants and liquid adhesive embolic agents can also be used if tissue necrosis is desired. Patient’s Clinical Condition A patient with pelvic hemorrhage from multiple sources and hemodynamic instability may need a rapid, lifesaving nonselective embolization procedure such as Gelfoam embolization of the internal iliac artery. In a hemodynamically stable patient, more time-consuming superselective coil embolization can be performed [1]. Before surgical splenectomy or in trauma patients with multiple intrasplenic pseudoaneurysms, proximal splenic embolization is safe and effective and can be achieved with coils or AVPs [34]. Contrary to this circumstance, splenic tissue infarction using particles is desired in hypersplenism and thrombocytopenia [1].

Case 1 Description A 42-year-old man presented with increasing abdominal pain after trauma. An interventional radiologist was consulted after CT and arteriography were performed (Fig. 2A). How will you proceed with embolization? Explanation Splenic arteriograms showed multiple small pseudoaneurysms (Fig. 2B). In consultation with the clinical service, the decision was made to proceed with proximal splenic artery embolization (SAE), which was performed using multiple 0.038-inch platinum coils (Fig. 2B). SAE decreases arterial pressure in the splenic artery, which facilitates pseudo­ aneurysm thrombosis [34, 35]. SAE can be performed proximally or superselectively. The main differences between the two techniques are listed in Table 2. Proximal SAE is indicated in patients with multiple intraparenchymal pseudoaneurysms or multiple active bleeding sites, whereas distal or superselective SAE is indicated in patients with isolated splenic lesions. Case 2 Description The interventional radiology department was consulted about treatment options for acute variceal bleeding in a 75-year-old man with cirrhosis after the initial medical measures had failed. TIPS was performed and follow-up portal venography (Fig. 3A) showed persistent filling of large gastric varices from the left and short gastric veins and portal vein thrombus. What options are available? Explanation Embolization of gastric varices may be required despite adequate portal decompression by TIPS [36]. These large-caliber vessels require permanent occlusion. Embolization of the two coronary veins using 10- and 12-mm AVP II was performed (Fig. 3B). Other alternatives include coils and liquid embolic agents. Also note that

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Embolization Agents

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a 12 × 60 mm uncovered stent (Wallstent, Boston Scientific) was placed for portal vein thrombus (Fig. 3B). Case 3 Description An 80-year-old woman was hypotensive after massive lower gastrointestinal tract bleeding. Selective superior mesenteric artery (SMA) and superselective right colic branch arteriograms are shown (Figs. 4A and 4B). Which embolic agent can be used? Explanation Selective SMA and superselective right colic branch arteriograms show active bleeding from a marginal branch (Figs. 4A and 4B). Superselective microcatheter embolization is recommended to preserve collateral flow and avoid bowel wall necrosis [37]. Microcoils are highly radiopaque, safe, and effective in superselective embolization of lower gastrointestinal tract bleeding [38, 39]. In coagulopathic patients, embolization using coils may require consolidation with PVA particles or gelatin sponge [37]. Arteriography performed after deployment of the microcoils shows control of bleeding (Fig. 4C). Case 4 Description A 48-year-old man with stage IV sarcoidosis and left upper lobe mycetoma presented with recurrent hemoptysis. Emergent bedside bronchoscopy showed blood coming from the left upper lobe bronchus. If you are consulted for emergent arteriography, how should you proceed? Explanation In more than 90% of cases of massive hemoptysis, the bronchial artery is the source [9, 40]. Bronchial arterial anatomy has many variations. Thoracic aortography is often performed for localizing bronchial arteries and determining their number and branching patterns and evaluating for nonbronchial systemic collaterals, which can be a potential cause of recurrent bleeding or therapy failure [9]. Selective bronchial arteriography often shows a hypertrophied and tortuous bronchial artery with diffuse distal hypervascularity, as seen in the present case (Fig. 5A). Always evaluate for spinal cord branches that course toward midline or may have hairpin turns (artery of Adamkiewicz) because inadvertent emboli-

zation of these branches can cause devastating spinal injury. Given that most cases of hemoptysis are caused by chronic lung disease or progressive neoplasm, embolization is usually performed using particles [40]. Because of the potential for intrapulmonary collaterals, the use of proximal coils may be ineffective and will also permanently “close the door” for future bronchial artery access and intervention. The use of particles larger than 325 µ theoretically reduces the risk of bronchopulmonary shunting [9]. Successful bronchial artery embolization is indicated by stasis (Fig. 5B). The use of liquid embolic agents has been reported, but these agents are not ideal because of the risk of tissue necrosis [40]. Case 5 Description A 43-year-old woman with an enlarging 7-cm right upper pole exophytic renal angiomyolipoma (Fig. 6A) was referred to interventional radiology for treatment. What are the treatment options? Explanation Angiomyolipoma is a benign hamartoma but can be complicated by bleeding that can quickly become life-threatening. The indications for embolization include bleeding, hemodynamic instability, or angiomyolipoma larger than 4 cm [41]. Transarterial embolization is a parenchyma-sparing technique that is effective in preventing hemorrhage and is the standard of care [42, 43]. Aortography is performed to evaluate for any accessory renal arteries and possible parasitized vessels. Selective renal arteriography is then performed in multiple projections to fully evaluate the vascular supply. Renal arteriography in this case showed an upper pole hypervascular tumor (Fig. 6A). Because tissue death of the angiomyolipoma is desired, a permanent embolic agent that can occlude at the capillary level—that is, ethanol mixed with Ethiodol in an approximately 2:1 ratio for radiopacity—is used for selective embolization [43] (Figs. 6B and 6C). Case 6 Description An 83-year-old woman developed right chylothorax (output = 1100 mL/d) after surgery for a mediastinal abscess. If you are consulted for thoracic duct embolization, how should you proceed?

Explanation Postoperative chylothorax and chylous ascites are uncommon complications but require prompt and aggressive management [44]. Lymphangiography alone (performed via either a conventional bipedal route or an accessing groin node) might be useful for the treatment of refractory chylous leaks [45]. Thoracic duct embolization or disruption after lymphangiography is an important alternative and is the firstline treatment of patients with traumatic and nontraumatic chylous leaks; no mortality, minimal morbidity, and a high success rate have been reported with this intervention [46, 47]. After imaging-guided percutaneous access of the thoracic duct has been achieved, coils are placed to provide a matrix for glue polymerization [46]. In this case, lymphangiography showed the cisterna chyli and thoracic duct with contrast extravasation (Ethiodol) along the right-sided surgical drain (Figs. 7A and 7B). The thoracic duct and cisterna chyli were accessed percutaneously and embolized below the level of the leak using 0.018-inch coils and a mixture of NBCA and Ethiodol (Fig. 7C). Case 7 Description A 65-year-old female pedestrian was hit by a car. CT showed pelvic fractures and active bleeding in the left gluteal region. Initial and delayed angiographic images are shown (Figs. 8A and 8B). What are the treatment options? Explanation Pelvic fractures with uncontrolled bleeding are associated with significant mortality and require aggressive treatment [48]. Transcatheter arterial embolization is a rapid and effective way to control hemorrhage associated with pelvic fractures [49]. Posttraumatic bleeding typically involves previously healthy vessels that undergo acute traumatic insult. Temporizing measures may be the only intervention that is required to give the vessel time to heal and stabilize the patient [50]. In this case, active bleeding noted from the posterior division of the internal iliac artery branches is extremely peripheral and the precise small branch cannot be identified or accessed. In scenarios like this one, particulate embolic agents such as Gelfoam can be used. An internal iliac arteriogram ob-

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Medsinge et al. tained after Gelfoam embolization shows no further bleeding (Fig. 8C). If the bleeding artery can be selected superselectively in a patient with an intact coagulation system, the use of microcoils is another effective option in the treatment of hemorrhage secondary to pelvic fracture. Conclusion A spectrum of embolic agents is available for use in vascular and nonvascular embolizations. Having a comprehensive understanding and practical knowledge of these agents is essential for optimal and safe use in different scenarios. A thorough knowledge of their mechanisms of action and adequate training in their use are important to minimize side effects and avoid potential catastrophic complications such as nontarget embolization. References 1. Binkert CA. Embolization tools and techniques. Appl Radiol 2002; 31(suppl 8):55–64 2. Greenfield AJ. Transcatheter vessel occlusion: selection of methods and materials. Cardiovasc Intervent Radiol 1980; 3:222–228 3. Vaidya S, Tozer KR, Chen J. An overview of embolic agents. Semin Intervent Radiol 2008; 25:204–215 4. Lopera JE. Embolization in trauma: principles and techniques. Semin Intervent Radiol 2010; 27:14–28 5. Kirby JM, Kachura JR, Rajan DK, et al. Arterial embolization for primary postpartum hemorrhage. J Vasc Interv Radiol 2009; 20:1036–1045 6. Lang EK. Transcatheter embolization in management of hemorrhage from duodenal ulcer: longterm results and complications. Radiology 1992; 182:703–707 7. Chrisman HB, Dhand S, Rajeswaran S, et al. Prospective evaluation of the embolic agent Bead Block in the treatment of uterine leiomyomas with uterine artery embolization: a phase II study. J Vasc Interv Radiol 2010; 21:484–489 8. Goodwin SC, Spies JB. Uterine fibroid embolization. N Engl J Med 2009; 361:690–697 9. Sopko DR, Smith TP. Bronchial artery embolization for hemoptysis. Semin Intervent Radiol 2011; 28:48–62 10. Lewis AL, Gonzalez MV, Lloyd AW, et al. DC bead: in vitro characterization of a drug-delivery device for transarterial chemoembolization. J Vasc Interv Radiol 2006; 17:335–342 11. Varela M, Real MI, Burrel M, et al. Chemoembolization of hepatocellular carcinoma with drug eluting beads: efficacy and doxorubicin pharmacokinetics. J Hepatol 2007; 46:474–481

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12. Laurent A, Beaujeux R, Wassef M, Rüfenacht D, Boschetti E, Merland J. Trisacryl gelatin microspheres for therapeutic embolization. I. Development and in vitro evaluation. AJNR 1996; 17:533–540 13. Beaujeux R, Laurent A, Wassef M, et al. Trisacryl gelatin microspheres for therapeutic embolization. II. Preliminary clinical evaluation in tumors and arteriovenous malformations. AJNR 1996; 17:541–548 14. Verret V, Ghegediban SH, Wassef M, Pelage JP, Golzarian J, Laurent A. The arterial distribution of Embozene and Embosphere microspheres in sheep kidney and uterus embolization models. J Vasc Interv Radiol 2011; 22:220–228 15. Sharma KV, Dreher MR, Tang Y, et al. Development of image-able beads for transcatheter embolotherapy. J Vasc Interv Radiol 2010; 21:865–876 16. Lewandowski RJ, Salem R. Yttrium-90 radioembolization of hepatocellular carcinoma and metastatic disease to the liver. Semin Intervent Radiol 2006; 23:64–72 17. Atassi B, Bangash AK, Bahrani A, et al. Multimodality imaging following 90Y radioembolization: a comprehensive review and pictorial essay. RadioGraphics 2008; 28:81–99 18. Ha-Kawa SK, Kariya H, Murata T, Tanaka Y. Successful transcatheter embolotherapy with a new platinum microcoil: the Berenstein liquid coil. Cardiovasc Intervent Radiol 1998; 21:297–299 19. Osuga K, Mikami K, Higashihara H. Principles and techniques of transcatheter embolotherapy for peripheral vascular lesions. Radiat Med 2006; 24:309–314 20. Van Ha TG. Use of the interlock fibered IDC occlusion system in clinical practice. Semin Intervent Radiol 2008; 25:3–10 21. Kallmes DF, Fujiwara NH. New expandable hydrogel-platinum coil hybrid device for aneurysm embolization. AJNR 2002; 23:1580–1588 22. Tuite DJ, Kessel DO, Nicholson AA, et al. Initial clinical experience using the Amplatzer vascular plug. Cardiovasc Intervent Radiol 2007; 30:650–654 23. Abdel Aal AK, Hamed MF, Biosca RF, Saddekni S, Raghuram K. Occlusion time for Amplatzer Vascular Plug in the management of pulmonary arteriovenous malformations. AJR 2009; 192:793–799 24. Wang W, Li H, Tam MD, Zhou D, Wang DX, Spain J. The Amplatzer Vascular Plug: a review of the device and its clinical applications. Cardiovasc Intervent Radiol 2012; 35:725–740 25. Maxwell NJ, Amer NS, Kiely ERD, Sweeney P, Brady AP. Renal artery embolisation in the palliative treatment of renal carcinoma. Br J Radiol 2007; 80:96–102 26. Sakuhara Y, Abo D, Hasegawa Y, et al. Preopera-

tive percutaneous transhepatic portal vein embolization with ethanol injection. AJR 2012; 198:914–922 27. Bittles MA, Hoffer EK. Gonadal vein embolization: treatment of varicocele and pelvic congestion syndrome. Semin Intervent Radiol 2008; 25:261–270 28. Gandini R, Konda D, Reale CA. Male varicocele: transcatheter foam sclerotherapy with sodium tetradecyl sulfate—outcome in 244 patients. Radiology 2008; 246:612–618 29. Tan KT, Kirby J, Rajan DK, Hayeems E, Beecroft JR, Simons ME. Percutaneous sodium tetradecyl sulfate sclerotherapy for peripheral venous vascular malformations: a single-center experience. J Vasc Interv Radiol 2007; 18:343–351 30. Rosen RJ, Contractor S. The use of cyanoacrylate adhesives in the management of congenital vascular malformations. Semin Intervent Radiol 2004; 21:59–66 31. Vanninen RL, Manninen I. Onyx, a new liquid embolic material for peripheral interventions: preliminary experience in aneurysm, pseudoaneurysm, and pulmonary arteriovenous malformation embolization. Cardiovasc Intervent Radiol 2007; 30:196–200 32. Lubarsky M, Ray CE, Funaki B. Embolization agents: which one should be used when? Part 1. Large-vessel embolization. Semin Intervent Radiol 2009; 26:352–357 33. Lubarsky M, Ray CE, Funaki B. Embolization agents: which one should be used when? Part 2. Small-vessel embolization. Semin Intervent Radiol 2010; 27:99–104 34. Raikhlin A, Baerlocher MO, Asch MR, Myers A. Imaging and transcatheter arterial embolization for traumatic splenic injuries: review of the literature. Can J Surg 2008; 51:464–472 35. Imbrogno BF, Ray CE. Splenic artery embolization in blunt trauma. Semin Intervent Radiol 2012; 29:147–149 36. Boyer TD, Haskal ZJ; American Association for the Study of Liver Diseases. The role of transjugular intrahepatic portosystemic shunt in the management of portal hypertension. Hepatology 2005; 41:386–400 37. Kickuth R, Rattunde H, Gschossmann J, Inderbitzin D, Ludwig K, Triller J. Acute lower gastrointestinal hemorrhage: minimally invasive management with microcatheter embolization. J Vasc Interv Radiol 2008; 19:1289–1296 38. Funaki B. Microcatheter embolization of lower gastrointestinal hemorrhage: an old idea whose time has come. Cardiovasc Intervent Radiol 2004; 27:591–599 39. Kuo WT, Lee DE, Saad WEA, Patel N, Sahler LG, Waldman DL. Superselective microcoil embolization for the treatment of lower gastrointesti-

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Downloaded from www.ajronline.org by 37.44.207.78 on 01/20/17 from IP address 37.44.207.78. Copyright ARRS. For personal use only; all rights reserved

Embolization Agents nal hemorrhage. J Vasc Interv Radiol 2003; 14:1503–1509 40. Lorenz J, Sheth D, Patel J. Bronchial artery embolization. Semin Intervent Radiol 2012; 29:155–160 41. Bishay VL, Crino PB, Wein AJ, et al. Embolization of giant renal angiomyolipomas: technique and results. J Vasc Interv Radiol 2010; 21:67–72 42. Kothary N, Soulen MC, Clark TW, et al. Renal angiomyolipoma: long-term results after arterial embolization. J Vasc Interv Radiol 2005; 16:45–50 43. Davis C, Boyett T, Caridi J. Renal artery embolization: application and success in patients with renal cell carcinoma and angiomyolipoma. Semin

Intervent Radiol 2007; 24:111–116 44. Kawasaki R, Sugimoto K, Fujii M, et al. Therapeutic effectiveness of diagnostic lymphangiography for refractory postoperative chylothorax and chylous ascites: correlation with radiologic findings and medical treatment. AJR 2013; 201:659–666 45. Chen E, Itkin M. Thoracic duct embolization for chylous leak. Semin Intervent Radiol 2011; 28:63–74 46. Cope C. Management of chylothorax via percutaneous embolization. Curr Opin Pulm Med 2004; 10:311–314 47. Hoffer EK, Bloch RD, Mulligan MS, Borsa JJ,

Fontaine AB. Treatment of chylothorax: percutaneous catheterization and embolization of the thoracic duct. AJR 2001; 176:1040–1042 48. Broadwell SR, Ray CE. Transcatheter embolization in pelvic trauma. Semin Intervent Radiol 2004; 21:23–35 49. Agolini SF, Shah K, Jaffe J, Newcomb J, Rhodes M, Reed JF 3rd. Arterial embolization is a rapid and effective technique for controlling pelvic fracture hemorrhage. J Trauma 1997; 43:395–399 50. Bauer JR, Ray CE. Transcatheter arterial embolization in the trauma patient: a review. Semin Intervent Radiol 2004; 21:11–22

Fig. 1—Permanent embolic devices. A, Magnified image shows Tornado microcoil (Cook Medical). Fibers attached to microcoil make it more thrombogenic. (Permission for use granted by Cook Medical Incorporated, Bloomington, Indiana) B, Image shows Amplatzer Vascular Plug II (St. Jude Medical), which is constructed from nitinol mesh, in fully expanded and opened state. (AMPLATZER and St. Jude Medical are trademarks of St. Jude Medical, Inc., or its related companies. Reprinted with permission of St. Jude Medical. © 2014 All rights reserved)

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Fig. 2—42-year-old man who presented with increasing abdominal pain after motor vehicular trauma. A, Splenic arteriogram with 5-French cobra catheter (with Waltman loop) shows multiple small contrast collections (circles) in spleen representative of multiple pseudoaneurysms. Also, perisplenic hematoma is indicated by medial displacement of spleen (arrow). B, Postembolization celiac arteriogram shows 0.038inch embolization coils (arrow) in proximal splenic artery. Distal splenic artery fills via collaterals, maintaining splenic viability.

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Medsinge et al. Fig. 3—75-year-old man with cirrhosis who presented with variceal bleed after failed medical management underwent placement of transjugular intrahepatic portosystemic shunt (TIPS). A, Portal venogram obtained after TIPS shows persistent filling of large gastric varices from left and short gastric veins (dashed arrows). Also note presence of portal vein thrombus (solid arrows). B, Portal venogram obtained after embolization of two gastric veins using 10- and 12-mm-diameter Amplatzer Vascular Plug II (St. Jude Medical) devices (dashed arrows) shows no further filling of varices. Stent (asterisk) was placed for thrombus in portal vein.

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Fig. 4—80-year-old woman who presented with hypotension and massive lower gastrointestinal tract bleeding. A, Selective superior mesenteric artery (SMA) arteriogram obtained using 5-French C2 catheter (Cobra) shows active bleeding from right colic artery branch (circle). B, Superselective right colic branch arteriogram obtained using microcatheter shows catheter tip at bleeding site (circle). C, Postembolization SMA arteriogram shows microcoils in place (circle) with no further bleeding.

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Fig. 5—48-year-old man with stage IV pulmonary sarcoidosis who presented with recurrent hemoptysis; bronchoscopy findings suggest left upper lobe is source. A, Selective left bronchial arteriogram shows hypertrophied and tortuous bronchial artery with diffuse distal hypervascularity. B, Left bronchial arteriogram obtained after embolization with 300- to 500-μ particles shows stasis.

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Embolization Agents

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Fig. 6—43-year-old woman who presented with enlarging 7-cm right upper pole exophytic angiomyolipoma. A, Right renal arteriogram shows hypervascular superior pole mass (circle) consistent with known angiomyolipoma. B, Arteriogram obtained after selective embolization of angiomyolipoma with mixture of alcohol and ethiodized oil (Ethiodol, Guerbet) shows cast of small blood vessels and markedly diminished vascularity. C, Postembolization renal arteriogram shows devascularized tumor and preserved flow to normal renal parenchyma.

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Fig. 7—83-year-old woman who presented with right chylothorax (output = 1100 mL/d) that developed after surgery for mediastinal abscess. A, Lymphangiogram obtained after accessing right groin node percutaneously (under ultrasound guidance) shows ethiodized oil (Ethiodol, Guerbet) within lymphatics (dashed arrow). B, Delayed fluoroscopic image over chest shows contrast extravasation along course of right-sided drainage catheter (dashed arrow) after traversing cisterna chyli and thoracic duct (solid arrow). C, Postembolization image obtained after fluoroscopy-guided percutaneous access of thoracic duct shows microcoils and glue mixed with Ethiodol within thoracic duct and cisterna chyli (dashed arrow).

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Medsinge et al.

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Fig. 8—65-year-old woman who sustained traumatic pelvic fracture. CT showed active bleeding in left gluteal region. A, Initial arterial phase left internal iliac arteriogram shows active bleeding from peripheral branch (circle). B, Delayed phase image shows more bleeding and additional focus of active bleeding (circles). Note peripheral location of bleeding. C, Left internal iliac arteriogram obtained after embolization using gelatin sponge (Gelfoam, Pharmacia & Upjohn) shows no bleeding.

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