Willis covered stent in the treatment of a recurrent blood blister-like aneurysm after pipeline implementation:A case report

Blood blister-like aneurysms(BBAs)are fragile and difficult to treat.However,the optimal treatment has yet to be determined.Pipeline embolization devices and Willis covered stent implementation are still controversial strategies for treating BBA.Herein,we report a case of recurrent BBA successfully treated with a Willis covered stent.A long-term follow-up angiography after the procedure indicated complete occlusion of the aneurysm.This case demonstrates the safety and efficacy of applying the Wills cover stent in the treatment of recurrent BBA after Pipeline implantation.

Efficacy of Willis covered stent of intracranial pseudoaneurysms in the internal carotid artery: A systematic review and meta-analysis

Objective:To evaluate the efficacy of a novel coated stent in the treatment of intracranial pseudoaneurysm.Methods:MEDLINE,EMBASE,and PubMed databases were searched for literature published between 1990 and April 2022 according to PRISMA guidelines.All studies with≥10 patients reporting successful implantation of Willis covered stent,therapeutic effect,complications,and postoperative follow-up were included.The combined incidence and corresponding 95%confidence intervals were assessed using a generalized linear mixed method and random effects model.Results:Five studies(116 patients with pseudoaneurysms)were included.The experimental groups in the selected studies showed a combined technical success rate of 81.03%(OR=18.31,95%CI=9.39-35.69,I^(2)=79%,P<0.001).Clinical follow-up showed that the complete cure rate was as high as 94.4%after the follow-up(OR=106.81,95%CI=39.08-291.88,I^(2)=0%,P=0.71).Conclusions:Willis covered stent is feasible,safe,and effective in the treatment of intracranial pseudoaneurysm.

Transjugular intrahepatic portosystemic shunt with covered stents for hepatocellular carcinoma with portal vein tumor thrombosis

AIM: To evaluate transjugular intrahepatic portosystemic shunt (TIPS) with covered stents for hepatocellular carcinoma (HCC) with main portal vein tumor thrombus (PVTT).

Drug-eluting fully covered self-expanding metal stent for dissolution of bile duct stones in vitro

BACKGROUND The treatment of difficult common bile duct stones(CBDS)remains a big challenge around the world.Biliary stenting is a widely accepted rescue method in patients with failed stone extraction under endoscopic retrograde cholangiopancreatography.Fully covered self-expanding metal stent(FCSEMS)has gained increasing attention in the management of difficult CBDS.AIM To manufacture a drug-eluting FCSEMS,which can achieve controlled release of stone-dissolving agents and speed up the dissolution of CBDS.METHODS Customized covered nitinol stents were adopted.Sodium cholate(SC)and disodium ethylene diamine tetraacetic acid(EDTA disodium,EDTA for short)were used as stone-dissolving agents.Three different types of drug-eluting stents were manufactured by dip coating(Stent I),coaxial electrospinning(Stent II),and dip coating combined with electrospinning(Stent III),respectively.The drugrelease behavior and stone-dissolving efficacy of these stents were evaluated in vitro to sort out the best manufacturing method.And the selected stonedissolving stents were further put into porcine CBD to evaluate their biosecurity.RESULTS Stent I and Stent II had obvious burst release of drugs in the first 5 d while Stent III presented controlled and sustainable drug release for 30 d.In still buffer,the final stone mass-loss rate of each group was 5.19%±0.69%for naked FCSEMS,20.37%±2.13%for Stent I,24.57%±1.45%for Stent II,and 33.72%±0.67%for Stent III.In flowing bile,the final stone mass-loss rate of each group was 5.87%±0.25%for naked FCSEMS,6.36%±0.48%for Stent I,6.38%±0.37%for Stent II,and 8.15%±0.27%for Stent III.Stent III caused the most stone mass-loss no matter in still buffer or in flowing bile,which was significantly higher than those of other groups(P<0.05).In vivo,Stent III made no difference from naked FCSEMS in serological analysis(P>0.05)and histopathological examination(P>0.05).CONCLUSION The novel SC and EDTA-eluting FCSEMS is efficient in diminishing CBDS in vitro.When conventional endoscopic techniques fail to remove difficult CBDS,SC and EDTA-eluting FCSEMS implantation may be considered a promising alternative.

Evaluation of fully covered self-expanding metal stents in benign biliary strictures and bile leaks

AIM: To investigate the use of fully covered metal stents in benign biliary strictures (BBS) and bile leaks. METHODS: We studied 17 patients, at Harbor-UCLA Medical center (Los Angeles), with BBS (n=12) and bile leaks (n=5) from July 2007 to February 2012 that had received placement of fully covered self-expanding metal stents (FCSEMs). Fourteen patients had endoscopic placement of VIABIL (Conmed, Utica, New York, United States) stents and three had Wallflex (Boston Scientific, Mass) stents. FCSEMS were 8 mm or 10 mm in diameter and 4 cm to 10 cm in length. Patients were followed at regular intervals to evaluate for symptoms and liver function tests. FCSEMS were removed after 4 or more weeks. Resolution of BBS and leak was documented cholangiographically following stent removal. Stent patency can be defined as adequate bile and contrast flow from the stent and into the ampulla during endoscopic retrograde cholangiopancreatography (ERCP) without clinical signs and/or symptoms of biliary obstruction. Criterion for bile leak resolution at ERCP is defined as absence of contrast extravasation from the common bile duct, cystic duct remanent, or gall blad-der fossa. Rate of complications such as migration, and instent occlusion were recorded. Failure of endoscopic therapy was defined as persistent biliary stenosis or continuous biliary leakage after 12 mo of stent placement. RESULTS: All 17 patients underwent successful FC- SEMS placement and removal. Etiologies of BBS included: cholecystectomies (n=8), cholelithiasis (n=2), hepatic artery compression (n=1), pancreatitis (n=2), and Whipple procedure (n=1). All bile leaks occurred following cholecystectomy. The anatomic location of BBS varied: distal common bile duct (n=7), common hepatic duct (n=1), hepaticojejunal anastomosis (n=2), right intrahepatic duct (n=1), and choledochoduo-denal anastomatic junction (n=1). All bile leaks were found to be at the cystic duct. Twelve of 17 patients had failed prior stent placement or exchange. Resolution of the biliary strictures and bile leaks was achieved in 16 of 17 patients (94%). The overall median stent time was 63 d (range 27-251 d). The median stent time for the BBS group and bile leak group was 62 ± 58 d (range 27-199 d) and 92 ± 81 d (range 48-251 d), respectively. All 17 patients underwent successful FCSEMS removal. Long term follow-up was obtained for a median of 575 d (range 28-1435 d). Complications occurred in 5 of 17 patients (29%) and included: migration (n=2), stent clogging (n=1), cholangitis (n=1), and sepsis with hepatic abscess (n=1). CONCLUSION: Placement of fully covered self-expanding metal stents may be used in the management of benign biliary strictures and bile leaks with a low rate of complications.

Fully covered metal biliary stents: A review of the literature

Fully covered self-expandable metal stents(FCSEMS)represent the latest advancement of metal biliary stents used to endoscopically treat a variety of obstructive biliary pathology.A large stent diameter and synthetic covering over the tubular mesh prolong stent patency and reduce risk for tissue hyperplasia and tumor ingrowth.Additionally,FCSEMS can be easily removed.All these features address issues faced by plastic and uncovered metal stents.The purpose of this paper is to comprehensively review the application of FCSEMS in benign and malignant biliary strictures,biliary leak,and post-sphincterotomy bleeding.

Fully covered self-expandable metal stents for treatment of malignant and benign biliary strictures

AIM:To present a series of covered self-expandable metal stents(CSEMS) placed for different indications and to evaluate the effectiveness,complications and extractability of these devices.METHODS:We therefore retrospectively reviewed the courses of patients who received CSEMS due to malignant as well as benign biliary strictures and postsphincterotomy bleeding in our endoscopic unit between January 2010 and October 2011.RESULTS:Twenty-six patients received 28 stents due to different indications(20 stents due to malignant biliary strictures,six stents due to benign biliary strictures and two stents due to post-sphincterotomy bleeding).Biliary obstruction was relieved in all cases,regardless of the underlying cause.Hemostasis could be achieved in the two patients who received the stents for this purpose.Complications occurred in five patients(18%).Two patients(7%) developed cholecystitis,stents dislocated/migrated in other two patients(7%),and in one patient(3.6%) stent occlusion was documented during the study period.Seven stents were extracted endoscopically.Removal of stents was easily possible in all cases in which it was desired using standard forceps.Twelve patients underwent surgery with pylorus preserving duodenopancreatectomy.In all patients stents could be removed during the operation without difficulties.CONCLUSION:Despite the higher costs of these devices,fully covered self-expanding metal stents may be suitable to relief biliary obstruction due to bile duct stenosis,regardless of the underlying cause.CSEMS may also represent an effective treatment strategy of severe post-sphincterotomy bleeding,not controlled by other measures.

Initiation behavior of covered explosive subjected to reactive fragment

Reactive fragment enhances lethality by incorporating the defeat mechanisms of kinetic energy and chemical energy into a unitary damage unit. Combined studies on the behavior of reactive fragment initiating covered explosive are performed theoretically and experimentally. The results in- dicate that the response of the covered explosive subjected to reactive fragment is not consistent with the classical shock initiation model. When impacting and penetrating into the covered explosive, the reactive fragment releases great amounts of thermo-chemical energy up to 5. 68 times of its kinetic energy into the explosive due to violent chemical reactions. This impact-induced chemical energy re- lease behavior of the reactive fragment significantly enhances the initiation capability and damage effects on the covered explosive.

Endovascular treatment of blood blister-like aneurysms in the internal carotid artery using a Willis covered stent

Background Despite the current availability of flow diverter devices(FDD), problems remains regarding optimal endovascular treatment(EVT) for blood blister-like aneurysms(BBAs) of the internal carotid artery(ICA). Objective To evaluate the safety and efficacy of EVT of BBAs in the ICA with a Willis covered stent. Methods 20 consecutive patients(5 men and 15 women) with ruptured BBAs underwent EVT using a Willis covered stent in two institutions from March 2013 to March 2018. Clinical observations, angiographic characteristics, and procedural and follow-up outcomes were retrospectively evaluated. Results 20 consecutive patients(5 men and 15 women) with ruptured BBAs underwent EVT using a Willis covered stent in two institutions from March 2013 to March 2018. Clinical observations, angiographic characteristics, and procedural and follow-up outcomes were retrospectively evaluated. Conclusion Our initial results demonstrate that reconstructive EVT using a Willis covered stent provides a viable approach to treat ICA BBAs. However, an expanded clinical evaluation and larger cohort are needed to confirm the results.

Use of fully covered self-expanding metal stents in benign biliary diseases

Biliary fully covered self-expanding metal stents (FCSEMS) are now being used to treat several benign biliary conditions. Advantages include small predeployment and large postexpansion diameters in addition to an easy insertion technique. Lack of imbedding of the metal into the bile duct wall enables removability. In benign biliary strictures that usually require multiple procedures, despite the substantially higher cost of FCSEMS compared with plastic stents, the use of FCSEMS is offset by the reduced number of endoscopic retrograde cholangiopancreatography interventions required to achieve stricture resolution. In the same way, FCSEMS have also been employed to treat complex bile leaks, perforation and bleeding after endoscopic biliary sphincterotomy and as an aid to maintain permanent drainage tracts obtained by means of Endoscopic Ultrasound-guided biliary drainage. Good success rates have been achieved in all these conditions with an acceptable number of complications. FCSEMS were successfully removed in all patients. Comparative studies of FCSEMS and plastic stents are needed to demonstrate efficacy and cost-effectiveness

Soil and Vegetation Spectral Coupling Difference (SVSCD) for Minerals Extraction from Hyperion Data in Vegetation Covered Area

Remote sensing data have been widely applied to extract minerals in geologic exploration, however, in areas covered by vegetation, extracted mineral information has mostly been small targets bearing little information. In this paper, we present a new method for mineral extraction aimed at solving the difficulty of mineral identification in vegetation covered areas. The method selected six sets of spectral difference coupling between soil and plant(SVSCD). These sets have the same vegetation spectra reflectance and a maximum different reflectance of soil and mineral spectra from Hyperion image based on spectral reflectance characteristics of measured spectra. The central wavelengths of the six, selected band pairs were 2314 and 701 nm, 1699 and 721 nm, 1336 and 742 nm, 2203 and 681 nm, 2183 and 671 nm, and 2072 and 548 nm. Each data set's reflectance was used to calculate the difference value. After band difference calculation, vegetation information was suppressed and mineral abnormal information was enhanced compared to the scatter plot of original band. Six spectral difference couplings, after vegetation inhibition, were arranged in a new data set that requires two components that have the largest eigenvalue difference from principal component analysis(PCA). The spatial geometric structure features of PC1 and PC2 was used to identify altered minerals by spectral feature fitting(SFF). The collecting rocks from the 10 points that were selected in the concentration of mineral extraction were analyzed under a high-resolution microscope to identify metal minerals and nonmetallic minerals. Results indicated that the extracted minerals were well matched with the verified samples, especially with the sample 2, 4, 5 and 8. It demonstrated that the method can effectively detect altered minerals in vegetation covered area in Hyperion image.

Double-layered covered stent for the treatment of malignant oesophageal obstructions: Systematic review and meta-analysis

AIM To investigate the efficacy of double-layered covered stent in the treatment of malignant oesophageal obstructions.METHODS A systematic review and meta-analysis was performed following the PRISMA process. Pub Med(Medline),EMBASE(Excerpta Medical Database),AMED(Allied and Complementary medicine Database),Scopus and online content,were searched for studies reporting on the Ni Ti-S polyurethane-covered double oesophageal stent for the treatment of malignant dysphagia. Weighted pooled outcomes were synthesized with a random effects model to account for clinical heterogeneity. All studies reporting the outcome of palliative management of dysphagia due to histologically confirmed malignant oesophageal obstruction using double-layered covered nitinol stent were included. The level of statistical significance was set at α = 0.05.RESULTS Six clinical studies comprising 250 patients in total were identified. Pooled technical success of stent insertion was 97.2%(95%CI: 94.8%-98.9%; I2 = 5.8%). Pooled complication rate was 27.6%(95%CI: 20.7%-35.2%; I2 = 41.9%). Weighted improvement of dysphagia on a scale of 0-5 scoring system was-2.00 [95%CI:-2.29%-(-1.72%); I2 = 87%]. Distal stent migration was documented in 10 out of the 250 cases examined.Pooled stent migration rate was 4.7%(95%CI: 2.5%-7.7%; I2 = 0%). Finally,tumour overgrowth was reported in 34 out of the 250 cases with pooled rate of tumour overgrowth of 11.2%(95%CI: 3.7%-22.1%; I2 = 82.2%). No funnel plot asymmetry to suggest publication bias(bias = 0.39,P = 0.78). In the sensitivity analysis all results were largely similar between the fixed and random effects models.CONCLUSION The double-layered nitinol stent provides immediate relief of malignant dysphagia with low rates of stent migration and tumour

Successful embolization assisted by covered stents for a pseudoaneurysm following pancreatic surgery

Delayed intra-abdominal hemorrhage after pancreatic surgery is a potentially lethal complication.Transarterial coil embolization and/or the placing of an endovascular stent are minimally invasive and effective procedures.An artery that is extensively eroded and rendered friable due to operative skeletonization or postoperative inflammation sometimes contributes to delayed intra-abdominal hemorrhage or rebleeding after coil embolization.This report presents a case of successful management of postoperative hemorrhage in a-74-year-old Japanese male.He experienced bleeding from a pseudoaneurysm of the brittle hepatic artery following total pancreatectomy.Initially the pseudoaneurysm was successfully treated with covered coronary stent-grafts,but rebleeding occurred 1 mo later due to the brittleness of the artery.Rebleeding was definitively managed by the complete packing of the stent by coil embolization.He remains stable at 18 mo following the f inal embolization.A stent graft can be used for protecting a brittle artery to avoid injury by coil embolization.

Reconstructive treatment of symptomatic vertebral artery dissecting aneurysms with Willis covered stent: Initial experience

Background:Symptomatic vertebral artery dissecting aneurysm(VADA)is a challenging disease with controversy on treatment strategy due to anatomic configuration and their nature.Moreover,the outcomes of reconstructive treatment have not been well established.Objective:To evaluate the safety and efficacy of reconstructive endovascular treatment(EVT)for symptomatic VADAs with Willis covered stent.Methods:We evaluated retrospectively 13 patients with symptomatic VADAs who treated with Willis covered stent,compared with stent-assisted coiling(SAC)on the characteristics,posttreatment course,angiographic and clinical follow-up outcomes at an average of 14.4 months(range,3-48 months).Results:A total of 33 patients with symptomatic VADAs were reviewed,23 of these patients with ruptured VADAs.The technical successful rate is 100%respectively in Willis covered stent(Group A)and SAC(Group B,n=20).The initial complete occlusion rate was significant higher in group A(100%)than group B(30%)(p<0.01).Major procedure-related complications were not significant different in the two groups.Serial follow-up angiograms revealed 5 recurrent VADAs in group B and no recurrence in group A(p>0.05).No obvious in-stent stenosis and no re-hemorrhage and delayed ischemic symptoms during the follow-up period.The final angiograms of all survived patients demonstrated the complete occlusion rate was higher in group A(100%)than group B(80%),but no significant statistical difference(p>0.05).Clinical outcomes were favorable in 31(93.9%),severe disability occurred in one in group B,and only one death in group A.The final clinical outcomes were also not significant difference in the two groups(p>0.05).Conclusions:Our initial result demonstrated reconstructive EVT with Willis covered stent provides a viable approach for selected symptomatic VADAs involving the intracranial and extracranial segments,which is similar to favorable results with SAC.However,an expanded clinical experiences and larger cohort studies are needed.

Using electrogeochemical approach to explore buried gold deposits in an alpine meadow-covered area

Exploration for buried gold ores and other deeply buried ores, especially in high altitude localities, is one of the tough challenges facing the geological world today.Fast and efficient ore prospecting methods are badly needed to deal with the situation. This paper documents a test that, for the first time, uses an electrogeochemical approach to prospect ores in the alpine meadow-covered Bangzhuoma area and its periphery in Qinghai–Tibet Plateau.The results were compared with conventional soil measurements from a 2 D prospection, and an ideal model of electrogeochemical anomaly formation in the area was established based on the comparison in order to provide theoretical guidance to buried ore prospecting in areas with similar conditions. The research shows that:(1) For exploration of deeply-buried mineral deposits, an electrogeochemical approach is better than soil measurements in terms of correspondence between element content values and anomaly forms and spatial distribution of known deposits in sections. Anomalies of high to low temperature element associations(Bi–Mo; Au–Ag–As–Bi and Au–Ag)and clear zonation were also observed along vertical vein runs in the sections. Based on integration of the observation with geological characteristics of the sections, we propose to use Au, Ag and As as the electrogeochemical indicators and Bi and Mo as the electrogeochemical tracing elementsto guide further analysis.(2) Judging from element statistics and the scale, intensity, and range of anomalies in plan maps, we found that an electrogeochemical approach is less affected by topography and secondary actions. The plan maps also show that elemental differentiation coefficients of the study area are in an ascending order of Ag(0.67) \ Mo(0.85) \ Bi(0.97) \ Au(1.51) \ As(2.35),better representing the element distribution in the area and yielding more striking and concentrated anomalies for known deposits than that of the soil measurements. Apart from that, electrogeochemical anomalies were observed in the south of lines 002 and 003 and the central of lines 008 and 009. We suggest the existence of deeply-buried mineral deposits based on analyses of element combinations and gold grade variations in samples taken from exploratory trenches in the area.(3) A three-stage(referring to the ore body dissolution, the mineralogenetic particle migration, and the mineralogenetic particle unloading) electrogeochemical ideal model was established for the study area, which takes into account moderate rainfall, high altitude, low air pressure, well-developed vegetation and roots, and an Upper Triassic Nieru Formation carbonaceous sandy slate as overburden.

Placement of a fully covered self-expandable metal stent in a young patient with chronic pancreatitis

Plastic stent insertion is a treatment option for pancreatic duct stricture with chronic pancreatitis.However, recurrent stricture is a limitation after removing the plastic stent.Self-expandable metal stents have long diameters and patency.A metal stent has become an established management option for pancreatic duct stricture caused by malignancy but its use in benign stricture is still controversial.We introduce a young patient who had chronic pancreatitis and underwent several plastic stent insertions due to recurrent pancreatic duct stricture.His symptoms improved after using a fully covered self-expandable metal covered stent and there was no recurrence found at follow-up at the outpatient department.

Preparation and Characterization of Graphite Powder Covered with CeO_2

In order to improve the wetting properties of graphite with Al melt and reduce the oxidation of the graphite, by which the segregation of components during the liquid-stir-casting process could be prevented. In this paper, a uniform thin nano-film of CeO2, about 20 nm thick, was successfully prepared onto graphite powder surface by heterogeneous nu-cleation process. The results show that an obvious chemical reaction did exit between CeO2 film and graphite with the formation of Ce-O-C bond, leading to a shift of the binding energy of C and Ce. The cover with CeO2 film illustrates a distinct change of surface state of graphite with a decrease of angle of contact.

Endovascular retrieval of a prematurely deployed covered stent

Several techniques have been reported to address different endovascular device failures. We report the case of a premature deployment of a covered balloon mounted stent during endovascular repair of a posttraumatic carotid-cavernous fistula(CCF). A 50-year-old male suffered a fall resulting in loss of consciousness and multiple facial fractures. Five weeks later, he developed decreased left visual acuity, proptosis, chemosis, limited eye movements and cranial/orbit bruit. Cerebral angiography demonstrated a direct left CCF and endovascular repair with a 5.0 mm × 19 mm covered stent was planned. Once in the lacerum segment, increased resistance was encountered and the stent was withdrawn resulting in premature deployment. A 3 mm × 9 mm balloon was advanced over an exchange length microwire and through the stent lumen. Once distal to the stent, the balloon was inflated and slowly pulled back in contact with the stent. All devices were successfully withdrawn as a unit. The use of a balloon to retrieve a prematurely deployed balloon mounted stent is a potential rescue option if leaving the stent in situ carries risks.

Endoleak management and postoperative surveillance following endovascular repair of internal carotid artery vascular diseases using Willis covered stent

Background:To report the clinical results and experiences of endoleak management and postoperative surveillance following endovascular repair of internal carotid artery vascular diseases(ICAVDs)using Willis covered stents.METHODS:Seventy-three patients with ICAVD who received Willis covered stent implantation between November 2013 and September 2018 were retrospectively reviewed.The clinical data of endoleak management and postoperative surveillance were analyzed.RESULTS:Seventy-three cases with ICAVD,including 57 aneurysms,11 carotid-cavernous sinus fistulas(CCF),and 5 surgical injuries,were all successfully installed with covered stents.Total isolation of ICAVDs was achieved in 59 patients(80.8%),and endoleaks were observed in 14 patients(19.2%).Of the 14 patients with endoleaks,12 had type I endoleaks and 2 had type II;13 had aneurysms and one had CCF.10 patients with type I endoleaks received balloon dilatation,and 7 of them underwent a second stent-graft implantation after then.One patient with type II endoleak received embolization of the branch artery,and another one received follow-up observation.Endoleaks resolved in 6 patients and were minimal in 5 patients after balloon dilatation or the second stent implantation.During the follow-up period,minor endoleaks spontaneously resolved in 4 patients and minimal endoleaks were still demonstrated in 4 patients without enlargement of residual lumen and rupture.CONCLUSIONS:Endoleaks are the major complication after endovascular repair of ICAVDs and represent one of the limitations of this procedure.Improving the understanding and management of endoleaks can be beneficial in the clinical setting,including the popularization and application of this technique.

Estimating Hydrogeological Parameters in Covered Carbonate Rocks Using a Discrete-State Compartment Model and Environmental Tritium

Nowadays, isotope environmental technique tends to be used as a reconnaissance tool , both qualitative and quantitative, to calculate the aquifer parameters particularly in carbonate rock aquifers. But, the heterogeneous flow is still problematic when Lumped parameter Models are usually used to calculate the residence times and hydraulic parameters. However, Discrete State Compartment Model can provide a powerful model to heterogeneous medium. One such study was carried on in Dazha valley, where the environmental tritium was used as a tracer for determining hydrogeological parameters based on a discrete state compartment model