Preliminary experience with precipitating hydrophobic injectable liquid in brain arteriovenous malformations

Liquid Embolic Agents for Endovascular Embolization: A Review

Endovascular embolization (EE) has been used for the treatment of blood vessel abnormalities, including aneurysms, AVMs, tumors, etc. The aim of this process is to occlude the affected vessel using biocompatible embolic agents. Two types of embolic agents, solid and liquid, are used for endovascular embolization. Liquid embolic agents are usually injectable and delivered into the vascular malformation sites using a catheter guided by X-ray imaging (i.e., angiography). After injection, the liquid embolic agent transforms into a solid implant in situ based on a variety of mechanisms, including polymerization, precipitation, and cross-linking, through ionic or thermal process. Until now, several polymers have been designed successfully for the development of liquid embolic agents. Both natural and synthetic polymers have been used for this purpose. In this review, we discuss embolization procedures with liquid embolic agents in different clinical applications, as well as in pre-clinical research studies.

Novel use of precipitating hydrophobic injectable liquid (PHIL) in pre-operative angioembolisation of a large posterior auricular arteriovenous malformation

BACKGROUND

Large arteriovenous malformations are often managed via endovascular embolisation followed by surgical resection. We describe the use of a new liquid embolic agent (LEA) - precipitating hydrophobic injectable liquid (PHIL) and its advantages over existing LEAs.

CASE

A 60-year-old male presented with a progressively enlarging right post-auricular arteriovenous malformation. He underwent successive angioembolisation with PHIL and subsequent surgical resection on post-embolisation day 1.

CONCLUSION

To our knowledge, this is the first reported case of PHIL being used in pre-operative embolization of a large extra-cranial head and neck AVM. Its excellent penetration into small calibre vessels, decreased glare artefact on imaging and decreased skin pigmentation render it a compelling alternative to existing LEAs.

Emerging Polymer Materials in Trackable Endovascular Embolization and Cell Delivery: From Hype to Hope

Minimally invasive endovascular embolization is a widely used clinical technique used for the occlusion of blood vessels to treat various diseases. Different occlusive agents ranging from gelatin foam to synthetic polymers such as poly(vinyl alcohol) (PVA) have been commercially used for embolization. However, these agents have some drawbacks, such as undesired toxicity and unintended and uncontrolled occlusion. To overcome these issues, several polymer-based embolic systems are under investigation including biocompatible and biodegradable microspheres, gelling liquid embolic with controlled occlusive features, and trackable microspheres with enhanced safety profiles. This review aims to summarize recent advances in current and emerging polymeric materials as embolization agents with varying material architectures. Furthermore, this review also explores the potential of combining injectable embolic agents and cell therapy to achieve more effective embolization with the promise of outstanding results in treating various devastating diseases. Finally, limitations and challenges in developing next-generation multifunctional embolic agents are discussed to promote advancement in this emerging field.

Embolic Materials: Understanding the Ocean of Choices

Embolization is a fundamental procedure that interventional radiologists perform on a daily basis to treat a variety of diseases. The disease processes for which embolization is considered a safe and effective treatment are continuously expanding, as are the embolization materials available for use. To achieve optimal clinical outcomes and minimize complications, it is imperative that the interventional radiologist understands the properties, strengths, and weaknesses of each class of embolic and specific embolic products. This is a continuous process as new materials are always becoming available. This article reviews the different classes of embolic materials, discusses strengths and weaknesses, and reviews areas of innovation.

The Common but Complicated Tool: Review of Embolic Materials for the Interventional Radiologist

Embolization is an important and widely utilized technique in interventional radiology. There are a variety of different categories and individual products which can be utilized to perform embolization. Understanding the different classes of embolic agents, the important features of each of these classes including strengths and limitations, and the variation in individual products within the classes is critical for interventional radiologist to practice safely and effectively. This article reviews the different kinds of embolics and relays some of the pertinent physical and chemical properties of individual products which should be considered when determining which embolic to select for a given purpose.

Glue, Onyx, Squid or PHIL? Liquid Embolic Agents for the Embolization of Cerebral Arteriovenous Malformations and Dural Arteriovenous Fistulas

Background

Endovascular embolization is an effective treatment option for cerebral arteriovenous malformations (AVMs) and dural arteriovenous fistulas (DAVFs). A variety of liquid embolic agents have been and are currently used for embolization of AVMs and DAVFs. Knowledge of the special properties of the agent which is used is crucial for an effective and safe embolization procedure.

Material and Methods

This article describes the properties and indications of the liquid embolic agents which are currently available: cyanoacrylates (also called glues), and the copolymers Onyx, Squid and PHIL, as well as their respective subtypes.

Results

Cyanoacrylates were the predominantly used agents in the 1980s and 1990s. They are currently still used in specific situations, for example for the occlusion of macro-shunts, for the pressure cooker technique or in cases in which microcatheters are used that are not compatible with dimethyl-sulfoxide. The first broadly used copolymer-based embolic agent Onyx benefits from a large amount of available experience and data, which demonstrated its safety and efficacy in the treatment of cerebral vascular malformations, while its drawbacks include temporary loss of visibility during longer injections and artifacts in cross-sectional imaging. The more recently introduced agents Squid and PHIL aim to overcome these shortcomings and to improve the success rate of endovascular embolization. Novelties of these newer agents with potential advantages include extra-low viscosity versions, more stable visibility, and a lower degree of imaging artifacts.

Conclusion

All the available liquid embolic agents feature specific potential advantages and disadvantages over each other. The choice of the most appropriate embolic agent must be made based on the specific material characteristics of the agent, related to the specific anatomical characteristics of the target pathology.

PHIL Migration to Internal Carotid Artery and Middle Cerebral Artery: Late Mechanical Retrieval with Solitaire AB Stent

Precipitating hydrophobic injecting liquid (PHIL) is a novel embolic agent used in the endovascular treatment of arteriovenous malformations (AVM) and arteriovenous fistulas. Complications can occur during embolization with migration of the liquid embolic material to normal vasculature. In these cases, use of a stent retriever is an option for removal of the plug. Herein, we present the case of a patient who presented with a right occipital hemorrhage due to a ruptured occipital AVM fed by the calcarine and parieto-occipital arteries with venous drainage to the straight sinus. Embolization via the anterior circulation through the right posterior communicating artery was attempted but PHIL migrated to right internal carotid artery and middle cerebral artery due to kinking and rupture of the microcatheter. The patient developed mild left hemiparesis. When this complication occurred, no stent retriever was available at our institution and 1 day later, the Solitaire AB stent was used to remove the plug of PHIL successfully, with good reperfusion of the proximal and distal vessels. The patient improved after the procedure and was discharged home without deficit. Mechanical stent retrievers can be used in cases of migration of liquid embolic agents to normal vasculature with good clinical and radiological results.

Simulation Model of Arteriovenous Malformation Embolization Using Onyx

Objective

Although Onyx has made effective embolization possible in the endovascular treatment of arteriovenous malformation (AVM), its infusion requires a high level of skill and experience. The purpose of this study is to create a simulation model that will help to solve this technical issue.

Model Presentation

Using data of 3D DSA images of a clinical case, an acrylonitrile-butadiene-styrene (ABS) resin model of the AVM was created with a 3D printer. Then, a hollow elastic model was created by applying silicone and eluting the ABS resin, which was finally connected to the human vascular model. Simulation of angiography and Onyx embolization using the model showed similar angiographic features and flow dynamics of contrast media and Onyx. During Onyx embolization, the plug and push technique could be performed as in a clinical case.

Conclusion

3D AVM model created with 3D printer enabled us to stimulate Onyx embolization of AVM.

Use of Phil Embolic Agent for Bleeding in Non-Neurological Interventions

Objective: To evaluate the safety and efficacy of the Phil liquid embolic agent in non-neurological embolization procedures. M&M: Thirty-five patients with a mean age of 62.5 years underwent percutaneous embolization using Phil for the treatment of visceral arterial bleedings in 20/35 patients (including three gluteal, one bladder, two superior mesenteric, three epigastric, one deep femoral, five internal iliac, four intercostal, and one lingual arteries), splanchnic pseudoaneurysms in 11/35 patients (including three hepatic, five splenic, and three renal arteries), pancreatic bleeding metastasis in 1/35 patient, and gastric bleeding varices in 3/35 patients. Phil is composed of a non-adhesive copolymer dissolved in DMSO (Anhydrous Dimethyl Sulfoxide) with different viscosity. Procedures were performed slowly under continuous fluoroscopic guidance to avoid embolization of non-target vessels. Results: Clinical success was obtained with a single intervention in 34 cases (97.15%), while a repeated procedure was required in one case (2.85%). No technical complications nor non-target embolization occurred. A case of post-embolic syndrome was noted (2.85%) in one patient. DMSO administration-related pain was successfully controlled by medical therapy. Conclusion: Phil can be considered a safe and effective embolic agent for the treatment of non-neurologic bleeding.

Long-term efficacy and safety of curative embolization of brain arteriovenous malformations using the dual microcatheter technique: A single-institution case series and literature review

OBJECTIVE

Brain arteriovenous malformations (bAVMs) are among the most common causes of cerebral hemorrhage in adolescents. For multiple-feeder bAVMs, complete exclusion of the nidus by endovascular embolization is challenging. This case series and literature review examined the long-term efficacy and safety of bAVM embolization using the dual microcatheter technique (DMCT).

METHODS

A total of 38 consecutive patients who underwent endovascular treatment for bAVMs with the DMCT along with all cases reported in the literature were retrospectively reviewed. Patient demographics, clinical presentation, bAVM angioarchitecture, treatment, complications, and long-term outcome were independently assessed.

RESULTS

Patients with bAVM (24 male and 14 female, mean age: 33.87 ± 13.70 years) treated at our institution were followed up for 97.76 ± 14.51 months. Angiographic obliteration was achieved in a single embolization session in 27/38 (71.05 %) cases; 4/38 (10.53 %) required multiple sessions, and 7/38 (18.42 %) underwent embolization combined with microsurgery or radiotherapy. Neurologic improvement at 90 days was observed in 29/38 patients (76.32 %). At the final follow-up, 34/38 patients (89.47 %) had a favorable clinical outcome. Two patients experienced recurrence during the follow-up period. In total, 55 patients were ultimately analyzed in our literature review. Complete exclusion of bAVMs was achieved in 35 patients (63.63 %), including in 54.54 % after a single endovascular treatment session. One patient died of hemorrhagic complication after endovascular treatment for an overall mortality rate of 1.82 %.

CONCLUSIONS

DMCT is safe for bAVM embolization and shows long-term efficacy, especially for multiple-feeder bAVMs.

Embolization of peripheral arteriovenous malformations and fistulas with precipitating hydrophobic injectable liquid (PHIL®)

PURPOSE

This paper reports on the preliminary experience of a single center in the embolization of peripheral AVMs and fistulas with precipitating hydrophobic injectable liquid (PHIL^®), focusing on technical aspects and short-term clinical outcomes.

MATERIALS AND METHODS

Seven males and five females were included in this study, mean age 42.16 years. For ten of them, it was the first embolization treatment; two had been previously treated with Onyx^® embolization. PHIL^® was injected with a transarterial approach without other embolics during the same procedure. Lesions were localized in small bowel (1), colon (1), head face (5), forefoot (1), uterus (1) and thorax (3); all were symptomatic. After 30-day clinical follow-up, a contrast-enhanced CT or MR was acquired at 3 months from intervention to detect eventual lesion residual.

RESULTS

After a single embolization procedure, complete technical success was obtained in 50%, while clinical improvement without additional therapies was appreciable in all patients. No technical failure occurred; in two cases, a small amount of PHIL^® proximally refluxed in nontarget vessels without clinical effects. No tattooing effects of superficial lesions neither artifacts at CT and cone-beam CT controls were evident.

CONCLUSIONS

PHIL^® seems to be a safe and effective liquid embolic agent for the treatment of peripheral AVMs and fistulas; although a direct comparison between PHIL and Onyx was not performed, PHIL might present the advantages of reduced artifacts at postprocedural CT scan and no need for shaking time preparation, but it is more expensive due to lower volume of product for each package and slightly less radiopaque at fluoroscopy.

Embolic Agents and Microcatheters for Endovascular Treatment of Cerebral Arteriovenous Malformations

Endovascular embolization of cerebral arteriovenous malformations (AVMs) originally entailed delivery of N-butyl cyanoacrylate glue to the nidus via a flow-directed microcatheter. Within the past decade, several new liquid embolic agents and novel microcatheter technologies have become available that have improved the ease of use and efficacy of endovascular therapies for AVMs. Nonadhesive copolymers, such as Onyx and Precipitating Hydrophobic Injectable Liquid, have largely replaced N-butyl cyanoacrylate given a lower risk of catheter entrapment. The emergence of balloon microcatheters has allowed for improved protection of the normal cerebral vasculature and has improved the penetration of liquid embolics into large AVMs, ultimately reducing procedure times and radiation exposure. Finally, several detachable tip microcatheters have been developed to facilitate removal of the catheter from hardened liquid embolic cast, preventing the morbidity associated with distal catheter entrapment. This article reviews the embolic agents and microcatheters currently available for the treatment of cerebral AVMs in the United States as well as the data demonstrating the safety and efficacy of these devices.

Transarterial embolization of the external carotid artery in the treatment of life-threatening haemorrhage following blunt maxillofacial trauma

Background

Severe bleeding after blunt maxillofacial trauma is a rare but life-threatening event. Non-responders to conventional treatment options with surgically inaccessible bleeding points can be treated by transarterial embolization (TAE) of the external carotid artery (ECA) or its branches. Case series on such embolizations are small; considering the relatively high incidence of maxillofacial trauma, the ECA TAE procedure has been hypothesized either underused or underreported. In addition, the literature on the ECA TAE using novel non-adhesive liquid embolization agents is remarkably scarce.

Patients and methods

PubMed review was performed to identify the ECA TAE literature in the context of blunt maxillofacial trauma. If available, the location of the ECA injury, the location of embolization, the chosen embolization agent, and efficacy and safety of the TAE were noted for each case. Survival prognostic factors were also reviewed. Additionally, we present an illustrative TAE case using a precipitating hydrophobic injectable liquid (PHIL) to safely and effectively control a massive bleeding originating bilaterally in the ECA territories.

Results and conclusions

Based on a review of 205 cases, the efficacy of TAE was 79.4–100%, while the rate of major complications was about 2–4%. Successful TAE haemostasis, Glasgow Coma Scale score ≥ 8 at presentation, injury severity score ≤ 32, shock index ≤ 1.1 before TAE and ≤ 0.8 after TAE were significantly correlated with higher survival rate. PHIL allowed for fast yet punctilious application, thus saving invaluable time in life-threatening situations while simultaneously diminishing the possibility of inadvertent injection into the ECA-internal carotid artery (ICA) anastomoses.

Intermixed Dimethyl-Sulfoxide-Based Nonadhesive Liquid Embolic Agents Delivered Serially via the Same Microcatheter for Cerebral AVM Treatment

BACKGROUND AND PURPOSE

Conventional nonadhesive liquid embolic agents currently are the criterion standard for endovascular embolization of cerebral AVMs. However, inadequate distal penetration into the nidus and unstable proximal plug formation are the major limitations of this approach and of the currently available embolic materials. The aim of this study was to evaluate the hypothetic efficacy of combining liquid embolic agents with different properties and viscosities for use in endovascular embolization of cerebral AVMs.

MATERIALS AND METHODS

From March 2018 to March 2019, sixteen patients with cerebral AVMs (12 women, 4 men; age range, 33-61 years) underwent endovascular embolization with combined liquid embolic agents delivered serially via a single microcatheter. The procedure consists of initial embolization with PHIL 30%, followed by Menox 18 through the same microcatheter. According to the Spetzler-Martin scale, 11 (68.75%) AVMs were grades I-II, 4 (25%) were grade III, and 1 (6.25%) was grade IV. Angiographic, technical, and clinical outcomes were analyzed independently.

RESULTS

Combined PHIL and Menox embolization through the same microcatheter via 21 pedicles was performed in these 16 patients. Once the length of the reflux reached approximately 2 cm, PHIL 30% was switched to Menox 18. Antegrade flow and distal penetration of the serially applied liquid embolic agents were observed in all 16 cases. The ability to completely control the flow of the materials and avoid any dangerous proximal reflux was noted in all performed embolizations. The estimated average size reduction of the treated AVMs was 85%, ranging from 50% to 100%. Complete embolization was achieved in 10/16 or 62.5% of the cases. There was no procedure-related complication during or after the embolization. No mortality or postprocedural clinical worsening was seen. Clinical success and complete obliteration were confirmed with at least 1 follow-up angiography in 10/16 patients.

CONCLUSIONS

Serial delivery of nonadhesive liquid embolic agents via the same microcatheter was safe and effective in our study and may be a potential technique for routine AVM treatment. However, further investigations are required to validate the safety and the efficacy of the method.

Advancements in the development on new liquid embolic agents for use in therapeutic embolisation

This review covers the current state-of-the-art in the development of liquid embolics for therapeutic embolisation.

Endovascular embolization of canine hepatic arteriovenous malformations using precipitating hydrophobic injectable liquid (PHIL) liquid embolic agent: a proof of concept study

Background

Hepatic arteriovenous malformations (HAVMs) are rare congenital lesions consisting of multiple high-pressure arteries feeding into low-pressure veins via a central nidus. Massive haemorrhage, portal hypertension and hepatic insufficiency can ensue. Endovascular embolization is increasingly a first line treatment method although there is no general consensus or guidelines on the most effective embolic agent or approach. We describe the novel treatment of two dogs with congenital hepatic AVMs using a modified version of the ‘pressure cooker’ technique often utilised in neurointervention with the DMSO-based PHIL embolic agent delivered via the DMSO compatible Scepter-XC dual lumen balloon catheter.

Case presentation

Two paediatric dogs were diagnosed with hepatic AVMs. Both dogs presented with ascites and abnormal liver function tests. CT angiograms revealed hepatic arterio-portal malformations arising from an enlarged celiac artery. Selective catheterisation of the artery supplying the AVM was achieved via a femoral artery approach. A Scepter XC dual-lumen compliant balloon microcatheter and Traxcess 0.014 guidewire combination was advanced to the nidus via through the 5Fr guide catheter towards the nidus. Inflation of the balloon occluded arterial inflow and PHIL was injected under continuous fluoroscopic screening until the PHIL embolic agent penetrated into the draining portal vein beyond the nidus.

In patient 1, normal portal venous waveform was restored with reversal of severe hepatic insufficiency. Whilst there was initial improvement post-operatively in patient 2 with normalisation of portal vein pressures and flow, opening of collateral nidus vessels re-established the high-pressure communication, and euthanasia was elected by the owner.

Conclusions

The ‘pressure cooker’ technique is a safe and efficacious approach to the treatment of canine HAVMs. The novel use of PHIL and the Scepter XC balloon catheter has several advantages over conventional endovascular approaches. Translational application to human paediatric interventions for similar conditions where embolic and contrast agent volume constraints are similar can be considered.

Advances in Biomaterials and Technologies for Vascular Embolization

Minimally invasive transcatheter embolization is a common nonsurgical procedure in interventional radiology used for the deliberate occlusion of blood vessels for the treatment of diseased or injured vasculature. A wide variety of embolic agents including metallic coils, calibrated microspheres, and liquids are available for clinical practice. Additionally, advances in biomaterials, such as shape-memory foams, biodegradable polymers, and in situ gelling solutions have led to the development of novel preclinical embolic agents. The aim here is to provide a comprehensive overview of current and emerging technologies in endovascular embolization with respect to devices, materials, mechanisms, and design guidelines. Limitations and challenges in embolic materials are also discussed to promote advancement in the field.

Precipitating hydrophobic injectable liquid (PHIL) embolic for the treatment of a uterine arteriovenous malformation: a technical report

OBJECTIVE

Uterine arteriovenous malformations (AVM) are unusual causes of vaginal bleeding. Although hysterectomy is the definitive treatment; uterine artery embolization (UAE) provides an alternative therapeutic option. This case presents a technical report of a uterine AVM treated successfully with transcatheter UAE using precipitating hydrophobic injectable liquid (PHIL) embolic agent.

CASE REPORT

A 41-year-old female, gravida 6, para 4, miscarriage 2, including a molar pregnancy 15 years prior, presented with massive per vaginal bleeding. Pelvic ultrasound demonstrated an acquired AVM as the underlying aetiology for her presentation. The patient underwent bilateral uterine arterial embolization. Four weeks later, there was nearly complete resolution of the AVM and the patient's menstrual cycle was restored 8 weeks after the procedure.

CONCLUSION

Uterine AVM can be treated safely and effectively with UAE using PHIL.

Liquid Embolic Agents in Spectral X-Ray Photon-Counting Computed Tomography using Tantalum K-Edge Imaging

The aim was to evaluate the potential of Spectral Photon-Counting Computed Tomography (SPCCT) to differentiate between liquid embolic agents and iodinated contrast medium by using tantalum-characteristic K-edge imaging. Tubes with a concentration series of tantalum and inserts with different concentrations of iodine were scanned with a preclinical SPCCT system. Tantalum density maps (TDM) and iodine density maps (IDM) were generated from a SPCCT acquisition. Furthermore, region-of-interest (ROI) analysis was performed within the tubes in the conventional CT, the TDM and IDM. TDM and IDM enable clear differentiation between both substances. Quantitative measurements of different tantalum concentrations match well with those of actually diluted mixtures. SPCCT allows for differentiation between tantalum and iodine and may enable for an improved follow-up diagnosis in patients after vascular occlusion therapy.

Single-stage planning for total cure of grade III-V brain arteriovenous malformations by embolization alone or in combination with microsurgical resection

PURPOSE

There are no established guidelines for treatment of Spetzler-Martin grade III-V brain arteriovenous malformations (bAVMs). The purpose of this study is to report our institutional experience in total obliteration/eradication of grade III-V bAVMs by single-stage planning of embolization combined with microsurgical resection when necessary.

METHODS

All patients harboring Spetzler-Martin (S-M) grade III-V bAVMs treated with single-stage planning between January 2006 and January 2018 were retrospectively reviewed. This treatment paradigm is applicable only to surgically accessible bAVMs and does not include deep-seated bAVMs. Indications for treatment, clinical presentation, imaging characteristics, and treatment outcomes were analyzed. Outcomes were assessed based on modified Rankin Scale.

RESULTS

A total of 31 patients were identified. Seventeen patients (54.8%) presented with hemorrhage, 10 (32.3%) with seizures, 3 (9.7%) with headaches, and 1 (3.2%) with progressive neurological deficit. Based on S-M grading system, 25 patients (80.6%) harbored grade III bAVM, 5 patients had grade IV bAVMs (16.1%), and 1 patient (3.2%) had a grade V bAVM. There were no treatment-related complications in 24/31 (77.4%) patients. Of the total of seven patients with complications, four patients had clinical deterioration. The long-term (> 6-month), non-disabling morbidity (mRS ≤ 2) rate was 6.5%. The long-term, disabling morbidity rate was 3.2% with a mortality of 3.2%. Complete angiographic obliteration was achieved in 30/31 (96.8%) patients.

CONCLUSION

Single-stage treatment strategy can be considered as an alternative to multistage embolization prior to surgery in grade III-V bAVMs. In this study, a high rate of total obliteration with relatively low rates of permanent morbidity and mortality was achieved.

Precipitating hydrophobic injectable liquid embolization of intracranial vascular shunts: initial experience and technical note

Precipitating hydrophobic injectable liquid is a new liquid embolic agent used mainly for intracranial neurointervention. The agent is ready to use (no shaking is required), since iodine, the radiopaque material, is covalently bonded into the compound. Additionally, due to the absence of tantalum, minimal artifacts are seen on postprocedure follow-up CT scans, and the agent penetrates into vessels smaller than 10 µm. The authors report their initial experience with the use of this agent in neurovascular intervention.

Initial experience with precipitating hydrophobic injectable liquid in cerebral arteriovenous malformations

BACKGROUND

Precipitating hydrophobic injectable liquid is a newly introduced liquid embolic agent for endovascular embolization with some technical advantages over other liquid embolic agents. We present our initial experience with precipitating hydrophobic injectable liquid in the endovascular treatment of cerebral arteriovenous malformations.

METHODS

From October 2015 to January 2018, 27 patients harboring cerebral arteriovenous malformations underwent endovascular embolization with precipitating hydrophobic injectable liquid 25. Clinical features, angiographic results, procedural details, complications, and follow-up details were retrospectively analyzed.

RESULTS

Twenty-seven patients with cerebral arteriovenous malformations were included. Total obliteration in one endovascular session was confirmed for 14/27 (52%) patients. Partial embolization was attained in 13 patients (48%) in whom staged treatment with following radiosurgery or surgery was planned. No mortality was recorded in this series. Complications during or after the embolization occurred in six of 27 (22.2%) patients.

CONCLUSION

In our initial experience, precipitating hydrophobic injectable liquid has acceptable clinical outcome comparable to other liquid embolic agents. Although this is the largest reported study in arteriovenous malformation treatment with precipitating hydrophobic injectable liquid, further studies are needed to validate its safety and efficacy.

Investigation of a New Version of the Liquid Embolic Agent PHIL with Extra-Low-Viscosity in an Endovascular Embolization Model

BACKGROUND AND PURPOSE

The type and composition of an embolic agent have a relevant influence on the performance of endovascular embolization. The aim of this study was to investigate a new version of the liquid embolic agent precipitating hydrophobic injectable liquid (PHIL) with extra-low-viscosity in an in vivo embolization model.

MATERIALS AND METHODS

Twenty-four embolization procedures were performed in the porcine rete mirabile. Eight embolizations were performed with PHIL 25% low viscosity, Squid 12, and standard PHIL 25%, respectively. Procedure time, required volume of embolic agent, visibility of the embolic agent, embolization control, embolization extent (ie, penetration of the rete mirabile), amount of reflux, and degree of embolization distal to the rete mirabile were assessed.

RESULTS

All embolic agents were adequately visible. The embolization extent was not significantly different among the 3 investigated agents; however, there was a tendency toward a higher embolization extent for PHIL 25% low viscosity (median embolization extent: 88% [PHIL 25% low viscosity]; 65% [Squid 12]; 60% [PHIL 25%]; P = .146). The amount of reflux was significantly lower for the extra-low-viscosity agents PHIL 25% low viscosity and Squid 12 compared with the standard PHIL 25% (median reflux distance: 8 mm [PHIL 25% low viscosity]; 6 mm [Squid 12]; 17 mm [PHIL 25%]; P = .011). All other embolization features did not differ among agents.

CONCLUSIONS

PHIL 25% low viscosity is a promising liquid embolic agent for endovascular embolization, featuring effective distal penetration, adequate visibility, a low amount of reflux, and good flow control.

Imaging artifacts of Onyx and PHIL on conventional CT, cone-beam CT and MRI in an animal model

BACKGROUND AND PURPOSE

A frequently reported drawback of ethylene vinyl alcohol copolymer-based liquid embolic agents is the production of artifacts in diagnostic imaging. New embolic agents, such as Precipitating hydrophobic injectable liquid (PHIL; MicroVention, Tustin, CA, USA), are supposed to induce significantly fewer artifacts. The purpose of this study is to assess the degree of artifacts induced by the liquid embolic agents Onyx (Medtronic Neurovascular, Irvine, CA, USA) and PHIL in conventional computed tomography (CT), cone-beam CT and magnetic resonance imaging (MRI) in an experimental in vivo model.

MATERIALS AND METHODS

In 10 pigs the rete mirabile was embolized with Onyx ( n = 5) or PHIL ( n = 5). After embolization, conventional CT, cone-beam CT and MRI were performed. The degree of artifacts was graded qualitatively (five-point scale; for CT and MRI) and quantitatively (HUs of well-defined regions of interest (ROIs); for CT only).

RESULTS

Artifacts were significantly more severe for Onyx both in the qualitative (e.g. conventional CT: 2 versus 5 (medians); p = 0.008) and in the quantitative image analysis (e.g. cone-beam CT: standard deviation of a ROI near to the embolic agent cast, 94 HU versus 38 HU (medians); p = 0.008). Neither Onyx nor PHIL produced any apparent artifacts in MRI.

CONCLUSION

PHIL produces fewer artifacts than Onyx in conventional CT and cone-beam CT in an experimental in vivo model.

Quantification of tantalum sedimentation rates in liquid embolic agents

Background Endovascular treatment (EVT) of brain arteriovenous malformations has evolved from cyanoacrylate derivatives such as N-butyl cyanoacrylate, an adhesive glue, to ethylene vinyl copolymer-based liquid embolics such as Onyx® and SQUID® dissolved in dimethyl sulfoxide. Although these agents offer several advantages, their rapidly decreasing radiopacity, as a result of the sedimentation of tantalum powder, compromises visual control during EVT. This study aims to quantify and compare tantalum sedimentation rates of several liquid embolic agents, and determine their effects on radiopacity. Methods The rate of sedimentation of liquid embolics Onyx 18®, SQUID 12®, and SQUID 18® was measured after preparation by single x-ray exposures for a period of 30 minutes. The signal-to-noise ratios (SNRs) of the suspension of each liquid embolic was calculated at various time points as tantalum settled out of the suspension. Precipitating Hydrophobic Injectable Liquid (PHIL®) was imaged as a control. Results Onyx 18® demonstrated the fastest sedimentation rate of the liquid embolics analyzed and demonstrated a threefold faster drop in SNR compared to SQUID 18® over 30 minutes. Onyx 18® demonstrated a one and a half times faster drop in SNR compared to SQUID 12®. Although PHIL 25® maintained constant SNR over the same time, it was lower at baseline immediately after preparation compared to tantalum-based liquids. Conclusion Caution during long injections using tantalum-based agents is advised. Onyx 18® has a significantly faster drop in radiopacity compared to SQUID 12® and SQUID 18®. Covalently bonded iodine-based embolics like PHIL® demonstrate constant radiopacity over time.

Conventional digital subtractional vs non-invasive MR angiography in the assessment of brain arteriovenous malformation

OBJECTIVES

Digital subtractional angiography (DSA) is the standard method for diagnosis, assessment and management of arteriovenous malformation in the brain. Conventional DSA (cDSA) is an invasive imaging modality that is often indicated before interventional treatments (embolization, open surgery, gamma knife). Here, we aimed to compare this technique with a non-invasive MR angiography (MRI DSA) for brain arteriovenous malformation (bAVM).

PATIENTS AND METHODS

Fourteen patients with ruptured brain AVM underwent embolization treatment pre-operation. Imaging was performed for all patients using MRI (1.5 T). After injecting contrast Gadolinium, dynamic MRI was performed with 40 phases, each phase of a duration of 1.2 s and having 70 images. The MRI results were independently assessed by experienced radiologist blinded to the cDSA.

RESULTS

The AVM nidus was depicted in all patients using cDSA and MRI DSA; there was an excellent correlation between these techniques in terms of the maximum diameter and Spetzler Martin grading. Of the fourteen patients, the drainage vein was depicted in 13 by both cDSA and MRI DSA showing excellent correlation between the techniques used.

CONCLUSION

MRI DSA is a non-invasive imaging modality that can give the images in dynamic view. It can be considered as an adjunctive method with cDSA to plan the strategy treatment for bAVM.

Extra-small dual-lumen micro-balloon catheters can improve endovascular embolization: an experimental in vivo and in vitro study

BACKGROUND

The embolization technique can have significant impact on the success of endovascular embolization.

OBJECTIVE

To evaluate the feasibility, embolization characteristics, and embolization extent with a newly developed extra-small micro-balloon catheter in an in vivo and in an in vitro embolization model in comparison with standard microcatheter embolizations.

MATERIALS AND METHODS

Twenty-eight embolization procedures were performed in the porcine rete mirabile (RM) and in an in vitro embolization model, using either an extra-small (distal outer diameter 1.6 F) dual-lumen micro-balloon catheter or a standard microcatheter. Precipitating hydrophobic injectable liquid (PHIL) was used as embolic agent. Procedure times, number of injections, required volume of embolic agent, and embolization extent (percentage of embolized RM in postinterventional X-ray scans or number of filled sections of the in vitro model) were assessed. Histopathological analyses were performed.

RESULTS

Total procedure time was significantly shorter (in vivo: 123 s vs 615 s (medians), P=0.001; in vitro: 180 s vs 496 s (medians), P=0.001), number of reflux events was significantly lower (in vivo: 0 vs 9 (medians), P=0.001; in vitro: 0 vs 3 (medians), P=0.001), and embolization extent was significantly higher (in vivo: 96.9% vs 65.6% (medians), P=0.011; in vitro: 26 vs 18 filled sections (medians); P=0.041) for the micro-balloon catheter groups. There was antegrade movement of the PHIL cast after balloon deflation in one in vitro embolization procedure and spontaneous balloon deflation with subsequent reflux in one in vivo embolization procedure.

CONCLUSION

Extra-small dual-lumen micro-balloon catheters can improve endovascular embolization in comparison with standard microcatheter embolization.

Eyelid arteriovenous malformation treated with pre-surgical embolization: A case report

Background Arteriovenous malformations are potentially serious vascular anomalies that are rarely encountered in the eyelid and require a multidisciplinary approach. Objectives We would like to describe the technical and clinical aspects related to the treatment of palpebral arteriovenous malformation with selective embolization, followed by surgical resection. Methods A 40-year-old patient presented with an isolated high-flow palpebral arteriovenous malformation. Transarterial embolization, using a liquid embolic agent (PHIL™), was performed in this patient. Results Angiographic and clinical follow-up revealed good results with clinical regression of the mass. Conclusion Although endovascular treatment of palpebral arteriovenous malformations is technically challenging, good functional and cosmetic result was achieved. Arteriovenous malformation embolization using PHIL™ seems to be very effective and makes subsequent surgical procedure safe and feasible. Level IV Evidence obtained from multiple time series with or without the intervention, such as case studies. Dramatic results in uncontrolled trials might also be regarded as this type of evidence.

Evaluation of a novel liquid embolic agent (precipitating hydrophobic injectable liquid (PHIL)) in an animal endovascular embolization model

BACKGROUND

The choice of the embolic agent and the embolization technique can have a significant impact on the success of endovascular embolization.

OBJECTIVE

To evaluate a novel iodinated copolymer-based liquid embolic agent (precipitating hydrophobic injectable liquid (PHIL)) in the porcine rete mirabile (RM), serving as an endovascular embolization model. Onyx, as an established liquid embolic agent, served as comparator.

MATERIALS AND METHODS

Sixteen embolization procedures were performed using PHIL (n=8) or Onyx (n=8) as liquid embolic agent. Waiting time between injections was set to 30 or 60 s (n=4 per study group). Survival time after intervention was 2 hours or 7 days. Embolization characteristics (eg, procedure times, number of injections and volume of embolic agent) and embolization extent (percentage of embolized RM in post-interventional x-ray) were assessed. Post-interventional CT and histopathological analyses were performed.

RESULTS

Embolization characteristics and embolization extent were not significantly different for PHIL and Onyx, including subgroups (eg, embolization extent 44% vs 69% (medians); p=0.101). For PHIL, extension of the waiting time from 30 to 60 s led to a significantly higher embolization extent (24% vs 72% (medians); p=0.035). Moderate disintegration and mild inflammation of the embolized blood vessels were present for both embolic agents.

CONCLUSION

PHIL is feasible for transarterial embolization in an acute and subacute endovascular embolization model. In this preliminary experimental in vivo study, embolization characteristics, embolization extent, and biocompatibility seem to be similar to those of Onyx.

Liquid Embolic Agents for Endovascular Embolization: Evaluation of an Established (Onyx) and a Novel (PHIL) Embolic Agent in an In Vitro AVM Model

BACKGROUND AND PURPOSE

Embolization plays a key role in the treatment of arteriovenous malformations. The aim of this study was to evaluate an established (Onyx) and a novel (precipitating hydrophobic injectable liquid [PHIL]) liquid embolic agent in an in vitro AVM model.

MATERIALS AND METHODS

An AVM model was integrated into a circuit system. The artificial nidus (subdivided into 28 honeycomb-like sections) was embolized with Onyx 18 (group Onyx; n = 8) or PHIL 25 (group PHIL; n = 8) with different pause times between the injections (30 and 60 seconds, n = 4 per study group) by using a 1.3F microcatheter. Procedure times, number of injections, embolization success (defined as the number of filled sections of the artificial nidus), volume of embolic agent, and frequency and extent of reflux and draining vein embolization were assessed.

RESULTS

Embolization success was comparable between Onyx and PHIL. Shorter pause times resulted in a significantly higher embolization success for PHIL (median embolization score, 28 versus 18; P = .011). Compared with Onyx, lower volumes of PHIL were required for the same extent of embolization (median volume per section of the artificial nidus, 15.5 versus 3.6 μL; P < .001).

CONCLUSIONS

While the embolization success was comparable for Onyx and PHIL, pause time had a considerable effect on the embolization success in an in vitro AVM model. Compared with Onyx, lower volumes of PHIL were required for the same extent of embolization.

Polymeric materials for embolic and chemoembolic applications

Percutaneous transcatheter embolization procedures involve the selective occlusion of blood vessels. Occlusive agents, referred to as embolics, vary in material characteristics including chemical composition, mechanical properties, and the ability to concurrently deliver drugs. Commercially available polymeric embolics range from gelatin foam to synthetic polymers such as poly(vinyl alcohol). Current systems under investigation include tunable, bioresorbable microspheres composed of chitosan or poly(ethylene glycol) derivatives, in situ gelling liquid embolics with improved safety profiles, and radiopaque embolics that are trackable in vivo. This article reviews commercially available materials used for embolization as well as polymeric materials that are under investigation.

Absence of skin discoloration after transarterial embolization of a subcutaneous auricular arteriovenous malformation with PHIL

BACKGROUND AND OBJECTIVE

One of the treatment options for arteriovenous malformations consists of embolization, with a choice of various embolic agents, with or without subsequent surgical excision. If embolization is offered without subsequent surgery, the embolic material will stay in situ, in which case the consistency and color become important in superficial lesions. The purpose of this case report is to describe if the use of a novel liquid embolic agent (PHIL) is well suited for treatment of superficial AVMs without subsequent surgery.

CASE DESCRIPTION

A 30-year-old male presented with a painful reddish, pulsatile swelling of the left ear that had been present for more than 10 years. Angiography confirmed an arteriovenous malformation supplied by the superficial temporal artery and the posterior auricular artery. The lesion was successfully treated by embolization with PHIL, through the superficial temporal artery. A minute residual shunt, from the posterior auricular artery, was accepted. Immediate disappearance of pulsatile tinnitus was reported. Moreover, return of normal skin color was observed without discomfort from the embolic deposits. This result has been stable throughout one year of clinical follow-up.

CONCLUSION

To our knowledge, this is the first case report describing PHIL embolization as a treatment option for superficial arteriovenous malformations without the necessity for subsequent surgery. The white color and rubbery consistency are beneficial characteristics of PHIL in treatment of subcutaneous lesions, especially in cosmetically relevant locations.