Embolic agents used for uterine fibroid embolization

The Role of Nanomedicine in Benign Gynecologic Disorders

Nanomedicine has revolutionized drug delivery in the last two decades. Nanoparticles appear to be a promising drug delivery platform in the treatment of various gynecological disorders including uterine leiomyoma, endometriosis, polycystic ovarian syndrome (PCOS), and menopause. Nanoparticles are tiny (mean size < 1000 nm), biodegradable, biocompatible, non-toxic, safe, and relatively inexpensive materials commonly used in imaging and the drug delivery of various therapeutics, such as chemotherapeutics, small molecule inhibitors, immune mediators, protein peptides and non-coding RNA. We performed a literature review of published studies to examine the role of nanoparticles in treating uterine leiomyoma, endometriosis, PCOS, and menopause. In uterine leiomyoma, nanoparticles containing 2-methoxyestradiole and simvastatin, promising uterine fibroid treatments, have been effective in significantly inhibiting tumor growth compared to controls in in vivo mouse models with patient-derived leiomyoma xenografts. Nanoparticles have also shown efficacy in delivering magnetic hyperthermia to ablate endometriotic tissue. Moreover, nanoparticles can be used to deliver hormones and have shown efficacy as a mechanism for transdermal hormone replacement therapy in individuals with menopause. In this review, we aim to summarize research findings and report the efficacy of nanoparticles and nanotherapeutics in the treatment of various benign gynecologic conditions.

Comparison of polyvinyl alcohol particles and tris-acryl gelatin microspheres embolic agents used in uterine artery embolization: A systematic review and meta-analysis

Objective

To identify the preferred agent by comparing the therapeutic efficacy, degree of infarction, and side effects of polyvinyl alcohol particles (PVA) and tris-acryl gelatin embolization (TAGM) agents in uterine artery embolization.

Materials and Methods

We included available articles comparing PVA with TAGM embolization agents in the management of fibroids. The primary outcomes included the decrease in uterine volume (%), decrease in dominant tumor volume (%), fibroid infarction rate, complete infarction fibroid, complications, pain score after 24 h, procedure time (minutes), duration of hospital stay, fluoroscopy time (minutes), and the change in symptom severity score.

Results

Eight articles that met our inclusion criteria were included in this study. Our analysis yielded an overall superiority of PVA compared to TAGM regarding complete fibroid infarction rate at the first 24 h. However, TAGM was better than PVA concerning <90% infarction rate outcome. While both embolization techniques showed similar effects regarding the change in symptom severity score, the percentage of decrease in uterine volume, percentage of decrease of dominant tumor volume, 90-99% infarction rate, complete infarction rate when assessed after the first 24 h, pain score after the first 24 h, procedure time, fluoroscopy time, minor, and major complications.

Conclusion

Both PVA and TAGM embolization agents are effective and safe modalities in treating patients with fibroids, with no significant variation of both agents in most outcomes.

Evaluation of the safety and efficacy of transarterial sevelamer embolization in a rabbit liver cancer model: A challenge on the size rule for vascular occlusion

As the most efficient method to treat hepatocellular carcinoma in the immediate or advanced stage, transarterial chemoembolization (TACE) is coming into the era of microsphere (MP). Drug-eluting beads have shown their huge potential as an embolic agent and drug carrier for chemoembolization, but their sizes are strictly limited to be above 40 μm, which was considered to occlude vessels in a safe mode. microsphere smaller than 40 µm is easy to be washed out and transported to the normal liver lobe or other organs, causing severe adverse events and failed embolization. To determine whether sevelamer ultrafine particle (0.2-0.5 µm) is qualified as a safe and efficient embolic agent, we investigated the safety and therapeutic efficiency of transarterial sevelamer embolization (TASE) in the VX2 rabbit liver cancer model, aiming to challenge the "40 µm" rule on the selection criteria of the MP. In a four-arm study, blank bead (Callisphere, 100-300 µm), luminescent polystyrene microsphere (10, 100 µm), and sevelamer particle were transarterially administered to evaluate the threshold size of the MP size for intrahepatic or extrahepatic permeability. Another four-arm study was designed to clarify the safety and efficiency of preclinical transarterial sevelamer embolizationTASE tests over other techniques. Sham (saline), TASE, C-TACE, and D-TACE (n = 6) were compared in terms of serum chemistry, histopathology, and tumor necrosis ratio. In the first trials, the "40 µm" rule was detectable on the VX2 cancer model, but the regulation has no application to the new embolic agent as sevelamer ultrafine particles have not been found to leak out from the VX2 lesions, only found in the embolized vessels. Pathology proves that less viable tumor residue was found 2 weeks after the procedure, evidencing a better therapeutic outcome. No adverse events were found except for a short stress response. These results indicate that sevelamer is a safe and efficient embolic as an alternative to the current MP-based embolization therapy techniques.

Immunomodulatory Biomaterials for Tissue Repair

All implanted biomaterials are targets of the host's immune system. While the host inflammatory response was once considered a detrimental force to be blunted or avoided, in recent years, it has become a powerful force to be leveraged to augment biomaterial-tissue integration and tissue repair. In this review, we will discuss the major immune cells that mediate the inflammatory response to biomaterials, with a focus on how biomaterials can be designed to modulate immune cell behavior to promote biomaterial-tissue integration. In particular, the intentional activation of monocytes and macrophages with controlled timing, and modulation of their interactions with other cell types involved in wound healing, have emerged as key strategies to improve biomaterial efficacy. To this end, careful design of biomaterial structure and controlled release of immunomodulators can be employed to manipulate macrophage phenotype for the maximization of the wound healing response with enhanced tissue integration and repair, as opposed to a typical foreign body response characterized by fibrous encapsulation and implant isolation. We discuss current challenges in the clinical translation of immunomodulatory biomaterials, such as limitations in the use of in vitro studies and animal models to model the human immune response. Finally, we describe future directions and opportunities for understanding and controlling the biomaterial-immune system interface, including the application of new imaging tools, new animal models, the discovery of new cellular targets, and novel techniques for in situ immune cell reprogramming.

No staghorn calculi and none/mild hydronephrosis may be risk factors for severe bleeding complications after percutaneous nephrolithotomy

Background

To explore the risk factors for severe bleeding complications after percutaneous nephrolithotomy (PCNL) according to the modified Clavien scoring system.

Methods

We retrospectively analysed 2981 patients who received percutaneous nephrolithotomies from January 2014 to December 2020. Study inclusion criteria were PCNL and postoperative mild or severe renal haemorrhage in accordance with the modified Clavien scoring system. Mild bleeding complications included Clavien 2, while severe bleeding complications were greater than Clavien 3a. It has a good prognosis and is more likely to be underestimated and ignored in retrospective studies in bleeding complications classified by Clavien 1, so no analysis about these was conducted in this study. Clinical features, medical comorbidities and perioperative characteristics were analysed. Chi-square, independent t tests, Pearson’s correlation, Fisher exact tests, Mann–Whitney and multivariate logistic regression were used as appropriate.

Results

Of the 2981 patients 70 (2.3%), met study inclusion criteria, consisting of 51 men and 19 women, 48 patients had severe bleeding complications. The remaining 22 patients had mild bleeding. Patients with postoperative severe bleeding complications were more likely to have no or slight degree of hydronephrosis and have no staghorn calculi on univariate analysis (p < 0.05). Staghorn calculi (OR, 95% CI, p value 0.218, 0.068–0.700, 0.010) and hydronephrosis (OR, 95% CI, p value 0.271, 0.083–0.887, 0.031) were independent predictors for severe bleeding via multivariate logistic regression analysis. Other factors, such as history of PCNL, multiple kidney stones, site of puncture calyx and mean corrected intraoperative haemoglobin drop were not related to postoperative severe bleedings.

Conclusions

The absence of staghorn calculi and a no or mild hydronephrosis were related to an increased risk of post-percutaneous nephrolithotomy severe bleeding complications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12894-021-00866-9.

Creation of an ex-vivo bovine kidney flow model for testing embolic agents: work in progress

Objectives

To develop an ex- vivo perfusion flow model using a bovine kidney for future testing of embolic agents in an inexpensive and easy way.

Methods

Six bovine adult kidneys were used for this study. Kidneys were cannulated and perfused via a roller pump. Three embolic agents, coils, Gelfoam, and a glue mixture of Histoacryl + Lipiodol, were deployed by targeting three secondary segmental arteries per kidney via a 5Fr catheter under fluoroscopic guidance. Cannulation time, success rate of segmental artery selection and embolic agent deployment, total operational time, and fluoroscopy dose were recorded.

Results

Average kidney weight was 0.752 +/− 0.094 kg. All six bovine kidneys were successfully cannulated in 21.6 min +/− 3.0 min. Deployment of coils and glue was achieved in every case (12/12); however, Gelfoam injection was not successful in one instance (5/6, 83%). Coil deployment demonstrated no embolic effect while Gelfoam and glue injections demonstrated decreased distal contrast filling post-embolization. Mean dose area product was 12.9 ± 1.8 Gy·cm2, fluoroscopy time was 10 ± 4 min and operational time was 27 ± 8 min.

Conclusions

We describe the creation of an ex vivo bovine kidney flow model for the preclinical evaluation of different embolic materials. The flow model can be modified to provide extensive bench testing and it is a promising tool for hands -on training in basic and advanced embolization techniques .

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.

Endovascular Embolization by Transcatheter Delivery of Particles: Past, Present, and Future

Minimally invasive techniques to occlude flow within blood vessels, initially pioneered in the 1970s with autologous materials and subsequently advanced with increasingly sophisticated engineered biomaterials, are routinely performed for a variety of medical conditions. Contemporary interventional radiologists have at their disposal a wide armamentarium of occlusive agents to treat a range of disease processes through a small incision in the skin. In this review, we provide a historical perspective on endovascular embolization tools, summarize the current state-of-the-art, and highlight burgeoning technologies that promise to advance the field in the near future.

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.

Efficacies of uterine artery embolization for symptomatic uterine fibroids using gelatin sponge: a single-center experience and literature review

AIM

The aim of this study was to retrospectively analyze the efficacies of uterine artery embolization (UAE) using gelatin sponge for symptomatic uterine fibroids.

METHODS

A series of 60 consecutive premenopausal women underwent UAE using gelatin sponge particles or porous gelatin particles. Patients were routinely followed up at 1, 3, 6, and 12 months after the procedure and asked to report any procedure-related complications. At each follow-up, an original clinical questionnaire was completed by the patients to evaluate changes in fibroid-related symptoms. Pelvic magnetic resonance imaging was performed before and at 3 and 12 months after the procedure, and the changes in volume of the dominant fibroid were calculated.

RESULTS

Bilateral UAE was successfully performed in all the patients. Median age was 45 years (range 34-53 years), and median follow-up period was 25.2 months (range 1-116 months). At the 3- and 12-month follow-up, the dominant fibroid volumes were found to be significantly decreased by 33.4% (95% confidence interval [CI]: 24.9-41.1) and 48.4% (95% CI: 40.7-56.1) compared to baseline volumes, respectively. Excluding patients not having menorrhagia or bulk-related symptoms, at 12 months 49 of 50 (98%) women showed improvement in menorrhagia, and 45 of 47 (95.7%) women showed improvement in bulk-related symptoms. During the follow-up period, ten patients (16.7%) required further interventions including two patients who had undergone hysterectomy. No sequelae were experienced by any of the patients.

CONCLUSION

UAE using gelatin sponge was associated with a high clinical success rate and good fibroid volume reduction compared to UAE using other embolic agents.

Uterine Artery Embolization for Symptomatic Myomata

Fibroid disease is common and causes significant health problems in women of childbearing age. Over the past several years, uterine artery embolization (UAE) has emerged as a minimally invasive treatment for symptomatic uterine myomata. Embolotherapy is effective in relieving myoma-related symptoms in 80% to 90% of patients. It requires shorter hospitalizations than traditional surgical therapies for myoma disease and is associated with faster recovery and lower complication risks than surgery. Patient selection, the UAE procedure, and post-UAE management are reviewed.

Feasibility, Safety, and Efficacy of Flow-Diverting Stent-Assisted Microsphere Embolization of Fusiform and Sidewall Aneurysms

BACKGROUND

Treatment of wide-necked internal carotid artery aneurysms is frequently associated with incomplete occlusion and high recurrence rates. Furthermore, platinum coils cause strong beam-hardening artifacts, hampering subsequent image analyses.

OBJECTIVE

To assess the feasibility, safety, and efficacy of flow-diverting, stent-assisted microsphere embolization of fusiform and sidewall aneurysms in vitro and in vivo.

METHODS

Using a recirculating pulsatile in vitro flow model, 5 different aneurysm geometries (inner/outer curve, narrow/wide neck, and fusiform) were treated (each n = 1) by flow-diverting stent (FDS) implantation and subsequent embolization through a jailed microcatheter using calibrated microspheres (500-900 μm) larger than the pores of the FDS mesh. Treatment effects were analyzed angiographically and by micro computed tomography. The fluid of the in vitro model was filtered to ensure that no microspheres evaded the aneurysm. The experiment was repeated once in vivo.

RESULTS

In vitro, all 5 aneurysms were safely and completely occluded by FDS-assisted microsphere embolization. Virtually complete aneurysm occlusion was confirmed by angiography and micro computed tomography. No microspheres escaped into the circulation. The experiment was successfully repeated in 1 pig with a sidewall aneurysm generated by vessel occlusion. An embolic protection system placed distally of the FDS in vitro and in vivo (each n = 1) contained no microspheres after the embolization. Thus, no microspheres were lost in the circulation, and the use of an embolic protection system seems feasible to provide additional safety.

CONCLUSION

FDS-assisted microsphere embolization of fusiform and sidewall aneurysms is feasible and yields virtually complete aneurysm occlusion while avoiding coil-associated beam-hardening artifacts.

A multicentre retrospective study of transcatheter angiographic embolization in the treatment of delayed haemorrhage after percutaneous nephrolithotomy

OBJECTIVE

The objective is to determine the timing and indications of transcatheter angiographic embolization (TAE) for delayed haemorrhage after percutaneous nephrolithotomy (PCNL).

METHODS

The medical records of 144 patients who underwent arteriography and TAE for delayed post-PCNL haemorrhage at five university hospitals between January 2005 and December 2012 were reviewed retrospectively.

RESULTS

The mean time to the onset of post-PCNL haemorrhage was 10.5 days (2 - 30 days). Clinical presentation included sudden onset bleeding in 51 patients (35.4 %), intermittent bleeding in 67 patients (46. 5 %), and continuous slow bleeding in 26 patients (18.1 %). Hemodynamic instability occurred in 32 patients (22.2 %). The mean haemoglobin decrease from the first post-PCNL day to the day of TAE was 49.5 g/L (31.0 - 79.0 g/L). Renal arteriography showed pseudoaneurysms in 69 (47.9 %) patients, arteriovenous fistulas in 28 (19.4 %) patients, mixed arterial and arteriovenous lesions in 17 (11.8 %) patients, arterial lacerations in 23 (16.0 %) patients, and negative angiographic finding in seven (4.9 %) patients. TAE was successful in stopping bleeding in all 137 patients with vascular lesions. There were no major complications associated with TAE.

CONCLUSIONS

TAE should be the recommended treatment for delayed post-PCNL haemorrhage in patients with hemodynamic instability and/or corrected haemoglobin decrease >30 g/L following conservative management.

KEY POINTS

• Delayed haemorrhage after percutaneous nephrolithotomy occurs more than 24 hours postoperatively. • Angio-embolization is a safe and effective treatment for delayed post-PCNL haemorrhage. • Angio-embolization can treat hemodynamic instability and/or corrected haemoglobin decrease >30 g/L.

Clinical and periprocedural pain management for uterine artery embolization

Uterine artery embolization has Level A data supporting excellent safety and efficacy in treating symptomatic uterine leiomyomata. However, there is a perception that either postprocedural pain is severe or poorly managed by the physician performing these procedures. This has led some primary care physicians to omit this procedure from the patients' options or to steer patients away from this procedure. A few simple techniques (pruning of the vascular tree and embolizing to 5-10 beat stasis) and fastidious pre-, intra-, and post-procedural management can nearly eliminate significant pain associated with embolization. Specifically, early implementation of long-acting low-dose narcotics, antiemetics and anti-inflammatory medications is critical. Finally, the use of a superior hypogastric nerve block, which takes minutes to perform and carries a very low risk, significantly reduces pain and diminishes the need for narcotics; when this technique was used in a prospective study, all patients were able to be discharged the day of the procedure. In the authors' experience, patients treated in this manner largely recover completely within 5 days and have a far less traumatic experience than patients traditionally treated with only midazolam (Versed) and fentanyl citrate (fentanyl) intraprocedurally, and narcotics and nonsteroidal antiinflammatory drugs postprocedurally.

Novel use of contrast-enhanced sonography in the diagnosis of central uterine necrosis following embolization for postpartum hemorrhage

Since 2007, we have identified 2 cases of central uterine necrosis after uterine arterial embolization for postpartum hemorrhage. Contrast-enhanced sonography showed an absence of enhancement of the internal myometrium. Magnetic resonance imaging with gadolinium confirmed the diagnosis. The images obtained for the first case were corroborated by histologic analysis from a hysterectomy done for sepsis. For the second case, contrast-enhanced sonography performed during a follow-up period of conservative treatment revealed a reduction of necrosis. Our study shows that contrast-enhanced sonography seems to be a useful examination as an adjunct to grayscale and power Doppler imaging in the diagnosis and follow-up of uterine necrosis.

Transcatheter arterial embolisation for the management of obstetric haemorrhage associated with placental abnormality in 40 cases

OBJECTIVE

To evaluate pelvic artery embolisation (PAE) in the emergency management of intractable postpartum haemorrhage (PPH) associated with placenta accreta (PA).

METHODS

Forty such patients (PAE for PPH/PA) were retrospectively reviewed. Medical records were reviewed regarding the delivery and PAE procedure. Follow-up gynaecological outcomes after PAE were obtained by telephone interviews.

RESULTS

Technical success was achieved in all women (100 %). The initial clinical success rate was 82.5 % (33/40). Three patients with PA underwent hysterectomy after PAE failed to stop the bleeding within 24 h after the embolisation. The other three patients underwent re-embolisation (two patients underwent re-embolisation on the next day and one patient had undergone re-embolisation 6 h after the first embolisation), and bleeding had stopped eventually. The clinical success rate was 92.5 %. There were four cases of immediate complications, such as, pelvic pain, nausea and urticaria. There were three late minor complications, temporary menopause, but no late major complications. After the procedure, 35 patients resumed normal menstruation, including two uncomplicated pregnancies. One patient expired owing to disseminated intravascular coagulopathy and intracerebral haemorrhage, despite successful embolisation.

CONCLUSION

PAE can be performed safely and effectively for patients with PPH and PA and can preserve the uterus in many patients.

Caesarean Scar Pregnancy: Treatment with Bilateral Uterine Artery Chemoembolization Combined with Dilation and Curettage

Objective:

This study investigated bilateral uterine artery chemo -embolization (BUACE) combined with dilation and curettage (D&C) in caesarean scar pregnancy (CSP).

Methods:

Nineteen women with CSP were referred for interventional radiology. In 13 patients, BUACE was performed before D&C, following a diagnosis of CSP. A further six patients received BUACE for massive vaginal bleeding after D&C for inevitable miscarriage; the diagnosis of CSP was subsequently confirmed ultrasonographically. BUACE of the uterine arteries was performed using gelfoam particles following intra-arterial infusion of 100 mg/m2 methotrexate.

Results:

BUACE was technically successful and immediate haemostasis was achieved in all patients. Blood loss was significantly greater during D&C undertaken before BUACE compared with D&C after BUACE, but this bleeding was controlled by BUACE. No patient required further surgical intervention and there were no severe complications. The gestational sac and placenta could no longer be detected ultrasonographically and the menstrual cycle returned to normal 2 - 3 months after treatment in all patients.

Conclusions:

BUACE followed by D&C seems to be a safe and effective treatment for CSP and should be considered as a treatment of choice.

Comparison of clinical outcomes of tris-acryl microspheres versus polyvinyl alcohol microspheres for uterine artery embolization for leiomyomas: results of a randomized trial

PURPOSE

To compare tris-acryl microspheres and polyvinyl alcohol (PVA) microspheres as embolic agents in uterine artery embolization (UAE) for uterine leiomyomas in terms of clinical outcome, inflammatory response, and adverse reactions.

MATERIALS AND METHODS

A double-blinded randomized controlled trial was performed, with 27 patients in the tris-acryl microsphere group and 29 in the PVA microsphere group. The primary endpoint was clinical success, defined as a 2-year freedom from subsequent surgery as a result of persistent or deteriorated symptoms. Secondary endpoints included (i) posttreatment leiomyoma enlargement, (ii) leiomyoma volume reduction at 3 and 9 months, (iii) significant residual intratumoral perfusion, (iv) increase in inflammatory and stress markers, (v) incidence of complications, and (vi) duration of hospital stay.

RESULTS

There was no statistically significant difference between the two groups in patient demographics, clinical presentation, initial tumor findings, change in inflammatory and stress markers after treatment, incidence of complications, and duration of hospital stay. Tris-acryl microspheres were associated with a higher rate of clinical success than PVA microspheres (96.3% [26 of 27] vs 69% [20 of 29]; P = .012), a lower incidence of posttreatment leiomyoma enlargement (P = .030), and a lower incidence of significant residual intratumoral perfusion (P = .030).

CONCLUSIONS

In the treatment of uterine leiomyomas, UAE with tris-acryl microspheres was associated with a higher clinical success rate, a lower incidence of tumor enlargement, and no significant differences in adverse reactions and inflammatory response compared with the use of PVA microspheres. Tris-acryl microspheres therefore represent the preferred agent for UAE of uterine leiomyomas.

Uterine artery embolization: a safe and effective, minimally invasive, uterine-sparing treatment option for symptomatic fibroids

Leiomyomas (or fibroids) are exceedingly common lesions. The indications to initiate treatment are based on the symptoms that can arise from their presence. In general, medical therapy should be considered the first line of treatment. Currently, the treatment of fibroids is in evolution. Since uterine artery embolization (UAE) was first described by Ravina et al in 1995, it has been shown to be a safe, efficacious, and cost-effective alternative to traditional surgical options, with data from long-term studies now available. Appropriate patient evaluation and selection are vital; the ideal candidate is one who is premenopausal, has symptomatic fibroids resistant to medical therapy, no longer desires fertility, and wishes to maintain her uterus. Uterine artery embolization is primarily an angiographic procedure, but periprocedural clinical management is critical for patient satisfaction. This article discusses the various embolic materials that are commonly used and available for UAE; understanding the technical nuances is critical for long-term success.

Uterine artery embolization for the treatment of adenomyosis: a review

During the past 10 years, uterine artery embolization (UAE) has been investigated as a possible therapy for adenomyosis. All publications available from 1999 through 2010 are included in this report. Levels of evidence and trial classifications were evaluated according to the guidelines developed by the United States Preventive Services Task Force. Long-term data are available from 511 affected women from 15 studies. Improvements were reported by 387 patients (75.7%). The median follow-up was 26.9 months. UAE as treatment for adenomyosis shows significant clinical and symptomatic improvements on a short- and long-term basis.

Midterm results of uterine artery embolization using narrow-size calibrated embozene microspheres

PURPOSE

To evaluate safety and efficacy of uterine artery embolization using narrow-size-range polyphosphazene-coated hydrogel microspheres (Embozene, CeloNova Biosciences, Newnan, GA).

METHODS

Between May 2006 and September 2008, a total of 121 consecutive patients (mean ± SD age 42.1 ± 5.4 years, range 30.5-51.5 years) were enrolled onto this single-center study. The primary study endpoint was safety as assessed by the society of interventional radiology (SIR) classification. The secondary endpoint was efficacy, which was based on a 1-year magnetic resonance imaging study and relief of symptoms documented by the Medical Outcomes Study 36-Item Short-Form Health Survey questionnaire over a 2-year interval.

RESULTS

The mean ± SD diameter of the dominant fibroid was 6.4 ± 2.6 (range, 2.9-13.9) cm and the mean volume 137.2 ± 245.1 (range, 5.3-1184) ml. Most patients had multiple fibroids with 11% more than 10. A total of 240 of 242 interventions were completed as planned, a technical success rate of 99.2%. According to the SIR classification, one type A, eight type C, and one type D complication occurred. Total devascularization was noted in 96% (116 of 121) of dominant fibroids. Volume decrease was 4% at 2 weeks, 52% (P < 0.001) at 3 months, 78% (P < 0.001) at 6 months, and 91% at 12 months (P < 0.001). The latter difference was statistically significant (P = 0.007). A total of 92% had improved hypermenorrhea at 1 year and 94% at 2 years. Dysmenorrhea was improved in 96% at 1 year and in 95% at 2 years. The overall health status score was 60.4 ± 26.2 points at baseline and 96.9 ± 3.8 after 1 year (P = 0.0019).

CONCLUSION

Uterine artery embolization with Embozene microspheres is a safe procedure. Its efficacy is demonstrated by high fibroid devascularization and volume reduction rates and significant improvements of clinical symptoms and quality-of-life scores during follow-up.

Observation of intravascular changes of superabsorbent polymer microsphere (SAP-MS) with monochromatic X-ray imaging

This study was designed to evaluate the intravascular transformation behavior of superabsorbent polymer microsphere (SAP-MS) in vivo macroscopically by using monochromatic X-ray imaging and to quantitatively compare the expansion rate of SAP-MS among different kinds of mixtures. Fifteen rabbits were used for our study and transcatheter arterial embolization (TAE) was performed for their auricular arteries using monochromatic X-ray imaging. We used three kinds of SAP-MS (particle diameter 100-150 mum) mixture as embolic spherical particles: SAP-MS(H) absorbed with sodium meglumine ioxaglate (Hexabrix 320), SAP-MS(V) absorbed with isosmolar contrast medium (Visipaque 270), and SAP-MS(S) absorbed with 0.9% sodium saline. The initial volume of SAP-MS particles just after TAE and its final volume 10 minutes after TAE in the vessel were measured to calculate the expansion rate (ER) (n = 30). Intravascular behavior of SAP-MS particles was clearly observed in real time at monochromatic X-ray imaging. Averaged initial volumes of SAP-MS (H) (1.24 x 10(7) microm(3)) were significantly smaller (p < 0.001) than those of SAP-MS (V) (5.99 x 10(7) microm(3)) and SAP-MS (S) (5.85 x 10(7) microm(3)). Averaged final volumes of SAP-MS (H) were significantly larger than averaged initial volumes (4.41 x 10(7) microm(3) vs. 1.24 x 10(7) microm(3); p < 0.0001, ER = 3.55). There were no significant difference between averaged final volumes and averaged initial volumes of SAP-MS (V) and SAP-MS (S). SAP-MS (H), which first travels distally, reaches to small arteries, and then expands to adapt to the vessel lumen, is an effective particle as an embolic agent, causing effective embolization.

Arterial distribution characteristics of Embozene particles and comparison with other spherical embolic agents in the porcine acute embolization model

PURPOSE

To determine the arterial distribution pattern of the embolic agent Embozene within the porcine kidney and compare it with those of other spherical embolic agents.

MATERIALS AND METHODS

Embozene, Embosphere, Bead Block, and Contour SE in size classes of 100-300 microm, 500-700 microm, and 700-900 microm and Embozene and Embosphere in the size class of 40-120 microm were used for total arterial occlusion in minipig kidneys. Organs were evaluated microscopically regarding vascular distribution of the different embolic agents and particle sizes.

RESULTS

The following variations of arterial distribution were identified. In the 40-120-microm size class, Embosphere particles penetrated significantly deeper compared with Embozene (P = .04). In the 100-300-microm size class, Bead Block showed a significantly deeper distribution as microscopy identified particles in arteries much smaller than their nominal size. In the 500-700-microm size class, Embosphere and Contour SE showed a deeper distribution. The most uniform arterial distribution was observed in the 700-900 microm size class,. However, few Embosphere and Contour SE particles were found in arcuate arteries, also indicating a distal distribution.

CONCLUSIONS

Throughout the four most-used size classes, from very small (40-120 microm) to large (700-900 microm), the distribution characteristics of the four tested materials vary substantially. Particularly, small Embosphere particles and small Bead Block particles showed a more distal distribution, as did medium-sized Embosphere and Contour SE particles. In the largest investigated size class, the distribution was more uniform. In general, the Embozene particles are very uniform in size, and they seem to reach vessels closely corresponding to their nominal size.

Analysis of nontarget embolization mechanisms during embolization and chemoembolization procedures

Complications of embolization and chemoembolization remain a problem even with the development of low-profile catheter material and the introduction of new embolization agents. In recent years many new embolization materials have become available for clinical use, so the possibilities and limitations of these new materials must be understood to allow safe and effective embolization. Although up to now some scientific work has been published reporting the basic risk of embolization procedures, the underlying pathomechanism remains the object of speculation. Besides complications like drug toxicity, allergic reactions, and bleeding of the puncture site, the characteristics of embolization materials must be known to understand the potential complications of nontarget embolization and reflux of embolization material. This article gives an overview of established and new embolization materials, their potential risks, and the underlying pathophysiology.

Rabbit VX2 tumors as an animal model of uterine fibroids and for uterine artery embolization

PURPOSE

To determine the suitability of the rabbit VX2 tumor animal model for uterine fibroids and uterine artery embolization (UAE).

MATERIALS AND METHODS

The authors implanted and grew one uterine VX2 tumor per rabbit in six rabbits. UAE was performed by using 100-300 microm embolic particles and confirmed with x-ray digital subtraction angiography, magnetic resonance (MR) imaging, and necropsy. Unenhanced and contrast medium-enhanced MR images of VX2 tumors were obtained before and after UAE. Relative MR signal-to noise-ratio (SNR) was measured in the uterine VX2 tumor and in normal uterine tissue before and after UAE and compared by using a paired t-test (P = .05).

RESULTS

VX2 uterine tumors were successfully grown, and both VX2 tumor presence in the uterus and UAE were seen angiographically and confirmed with necropsy in all six rabbits. Statistically significant reductions in relative SNRs were measured in tumors (SNR before UAE, 15.3 +/- 5.15; SNR after UAE, 3.84 +/- 3.94; P < .0001). No statistically significant decrease in SNR was measured in normal uterine tissue before and after UAE (P = .63 for the right uterine horn and P = .93 for the left uterine horn).

CONCLUSION

Rabbit VX2 uterine tumors may be a suitable animal model of uterine fibroids and UAE.