17 research outputs found

    Role of Excess Bi on the Properties and Performance of BiFeO<sub>3</sub> Thin-Film Photocathodes

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    BiFeO3 (BFO) has recently been identified as a promising photocathode material for photoelectrochemical (PEC) water splitting due to its light absorption and photoelectrochemical properties. The performance-limiting factors, in particular the impact of stoichiometry on the performance, still need to be understood. The effect of the ratio of Bi/Fe in the precursor solution for sol-gel synthesis on the properties and performance of BFO thin films is investigated in this study. Thin films with a stoichiometric Bi/Fe ratio and with a 10% excess of Bi are prepared on fluorine-doped tin-oxide substrates. While bulk characterization techniques show the formation of phase-pure BFO, surface characterization techniques indicate Bi enrichment on the surface. Light absorption and band gap do not change with excess Bi, whereas the current density is two times higher for Bi excess films compared to stoichiometric films at 0.6 V vs RHE. Electrochemical impedance spectroscopy attributes this improved performance of excess Bi thin films to a lower recombination rate and a lower charge transfer resistance. The lower recombination rate is attributed to fewer Bi and O vacancies, which can act as recombination centers. Therefore, adjusting the Bi/Fe ratio is an effective strategy to enhance the PEC performance of BFO photocathodes.</p

    Acute Endovascular Treatment of Patients With lschemic Stroke From Intracranial Large Vessel Occlusion and Extracranial Carotid Dissection

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    Introduction: Carotid artery dissection (CAD) and atherosclerotic carotid artery occlusion (ACAO) are major causes of a tandem occlusion in patients with intracranial large vessel occlusion (LVO). Presence of tandem occlusions may hamper intracranial access and potentially increases the risk of procedural complications of endovascular treatment (EVT). Our aim was to assess neurological, functional and technical outcome and complications of EVT for intracranial LVO in patients with CAD in comparison to patients with ACAO and to patients without CAD or ACAO. Methods: We analyzed data of the MR CLEAN trial intervention arm and MR CLEAN Registry, acquired in 16 Dutch EVT-centers. Primary outcome was the change in stroke severity by comparing the National Institute of Health Stroke Scale (NIHSS) score at 24-48 h after treatment vs. baseline. Secondary outcomes included reperfusion rate and symptomatic intracranial hemorrhage (sICH). We compared outcomes and complications between patients with CAD vs. patients with ACAO and patients without CAD or ACAO. Results: In total, we identified 74 (4.7%) patients with CAD, 92 (5.9%) patients with ACAO and 1398 (89.4%) patients without CAD or ACAO. Neurological improvement at short-term after EVT in patients with CAD was significantly better compared to ACAO (raw mean -5 vs. mean -1 NIHSS point; p = 0.03) and did not differ compared to patients without CAD or ACAO (-4 NIHSS points; p = 0.62). Rates of successful reperfusion in patients with CAD (47%) was comparable to patients with ACAO (47%; p = 1.00), but was less often achieved compared to patients without CAD or ACAO (58%; p = 0.08). Occurrence of sICH did not differ significantly between CAD patients (5%) and ACAO (11%; p = 0.33) or without CAD/ACAO (6%; p = 1.00). Conclusion: EVT in patients with intracranial LVO due to CAD results in neurological improvement comparable to patients without tandem occlusions. Therefore, carotid artery dissection by itself should not be a contraindication for endovascular treatment in stroke patients with intracranial large vessel occlusion. Although more challenging endovascular procedures are to be suspected in both patients with CAD or ACAO, accurate distinction between CAD and ACAO might influence clinical decision making as better clinical outcome can be expected in patients with CAD

    99mTc-labelled macroaggregated albumin (MAA) scintigraphy for planning treatment with 90Y microspheres

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    Y-90 microspheres are used for intra-arterial treatment of liver tumours. In the patient preparation, a hepatic angiogram is performed and all arteries that could transport microspheres from the targeted liver vasculature to extrahepatic organs are blocked. Tc-99m-labelled macroaggregated albumin (MAA) is injected intra-arterially to simulate the treatment and whole-body scintigraphy and single photon emission computed tomography (SPECT) of the abdomen are performed. Various aspects of lung shunt fraction (LSF) estimation were studied: interobserver and intrapatient variability, influence of scan quality and underlying disease. Secondly, the interobserver variability in reading the MAA SPECT of the abdomen was investigated. We reviewed 90 whole-body scans and 20 SPECT scans performed at our institution. Readers were blinded to each other's findings. Scoring the scan quality was based on the visualization of tracer degradation. The mean difference in LSF between the readers was 1%. In 1 of 23 patients who underwent repeated MAA injections a marked change in LSF was observed. No significant differences in LSF were recorded for primary versus secondary liver tumours. There was a correlation between scan quality and LSF, suggesting that low scan quality leads to overestimation of the LSF. Concordant results in ruling out the presence of extrahepatic tracer deposition were reached in 17 of 20 scans (85%). Interobserver and intrapatient variability in LSF calculation was limited. LSF was clearly dependent on scan quality. The underlying disease had no significant impact on the LSF. Interobserver variability for reading the MAA SPECT scans was acceptable

    Intra-arterial treatment with 90Y microspheres for hepatocellular carcinoma: 4 years experience at the Ghent University Hospital

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    Purpose We report on our experience in terms of eligibility, safety, response and survival for treatment of hepatocellular carcinoma (HCC) with (90)Y microspheres. Secondly, we investigated the urinary excretion of (90)Y following treatment. Methods We retrospectively reviewed all HCC patients referred to our department for (90)Y microsphere treatment. We recorded reasons for not proceeding to actual treatment. In case treatment was performed, we assessed the tolerance (Common Terminology Criteria for Adverse Events v3.0, CTCAE v3.0), the response [modified Response Evaluation Criteria in Solid Tumors (mRECIST) criteria] and long-term survival (Kaplan-Meier). The urinary excretion was estimated by 12-h urine collections post-injection for analysis in a gamma counter. Results Forty-three HCC patients were referred for radio-embolization. Fourteen patients were excluded, mainly due to unfavourable (99m)Tc-macroaggregated albumin (MAA) distribution. Twenty-nine patients were treated with (90)Y microspheres (TheraSphere, mean activity 2.17 GBq). In four patients severe clinical adverse events were encountered, however only in one case clearly related to the therapy. Twenty patients were assessable by mRECIST: complete response in 15%, partial response in 35%, stable disease in 30% and progression in 20% were observed. A median survival of 12.3 months (95% confidence interval 9.4-15.2) was estimated. Concerning the substudy on urinary excretion, only 0.0025% of the administered activity was excreted in the urine within the first 12 h following TheraSphere. Conclusion Following a strict workup before admitting patients to radioembolization with TheraSphere, we found good clinical tolerance in the vast majority of patients. Radiological response assessment yielded an overall response rate of 50%, when evaluated early following treatment. Urine analysis showed consistently only low activities of (90)Y excreted in the urine

    Transsinusoidal portal vein embolization with ethylene vinyl alcohol copolymer (Onyx): a feasibility study in pigs

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    Portal vein embolization is performed to increase the future liver remnant before liver surgery in patients with liver malignancies. This study assesses the feasibility of a transsinusoidal approach for portal vein embolization (PVE) with the ethylene vinyl alcohol copolymer, Onyx. Indirect portography through contrast injection in the cranial mesenteric artery was performed in eight healthy pigs. Onyx was slowly injected through a microcatheter from a wedged position in the hepatic vein and advanced through the liver lobules into the portal system. The progression of Onyx was followed under fluoroscopy, and the extent of embolization was monitored by indirect portography. The pigs were euthanized immediately (n = 2), at 7 days (n = 4), or at 21 days postprocedure (n = 2). All pigs underwent necropsy and the ex vivo livers were grossly and histopathologically analyzed. Transsinusoidal PVE was successfully performed in five of eight pigs (63%). In 14 of 21 injections (67%), a segmental portal vein could be filled completely. A mean of 1.6 liver lobes per pig was embolized (range 1-2 lobes). There were no periprocedural adverse events. Focal capsular scarring was visible on the surface of two resected livers, yet the capsules remained intact. Histopathological examination showed no signs of recanalization or abscess formation. Mild inflammatory reaction to Onyx was observed in the perivascular parenchyma. The porcine portal vein can be embolized through injection of Onyx from a wedged position in the hepatic vein. Possible complications of transsinusoidal PVE and the effect on contralateral hypertrophy need further study

    Safety and Outcome of Endovascular Treatment for Minor Ischemic Stroke: Results From the Multicenter Clinical Registry of Endovascular Treatment of Acute Ischemic Stroke in the Netherlands

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    Goal: Insufficient data is available about safety and efficacy of endovascular treatment (EVT) in patients with minor stroke symptoms because these patients were excluded from most randomized trials. We aimed to compare characteristics, functional outcome, and complications in patients with minor ischemic stroke National Institutes of Health Stroke Scale score ≤5 (NIHSS score ≤5) and moderate to severe ischemic stroke (NIHSS score ≥6) due to intracranial proximal artery occlusion of the anterior circulation who underwent EVT. Materials and Methods: We report patients with an anterior circulation occlusion who were included between March 2014 and June 2016 in the multicenter randomized clinical trial of EVT of acute ischemic stroke in the Netherlands Registry, a prospective, multicenter, observational study for stroke centers that perform EVT in the Netherlands. Minor ischemic stroke was defined as baseline NIHSS score of 5 or less. Primary outcome is the modified Rankin Scale (mRS) score at 90 days. Secondary outcomes include symptomatic intracranial hemorrhage (sICH) and mortality. Findings: Seventy-one (5.5%) patients had a NIHSS score of 5 or less. Functional independence (mRS 0-2 at 90 days) was reached in 75% of these patients, compared to 40% of patients with NIHSS score of 6 or more. sICH occurred in 4% of patients, of which 1% occurred peri-interventionally. Death occurred in 6% of patients. Conclusions: Patients with minor ischemic stroke with an intracranial proximal arterial occlusion of the anterior circulation who underwent EVT have a high chance of favorable outcome and appear to have low occurrence of treatment-related sICH. Therefore, our results encourage the use of EVT for minor ischemic stroke in the absence of effect estimates from controlled studies
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