Stent-assisted coiling of unruptured intracranial aneurysms: long-term follow-up in 164 patients with 183 aneurysms.

PURPOSE: Stent-assisted coiling (SAC) is increasingly used to treat complex unruptured intracranial aneurysms (UIA) including wide-necked and fusiform IA. However, few data are available over the long-term results of this technique. We report our 9-year-experience of SAC of UIA. METHODS: A retrospective review of our prospectively maintained database identified all patients treated by SAC for an UIA in 2 institutions. The clinical charts, procedural data and angiographic results were reviewed. RESULTS: Between 2004 and 2012, we identified 164 patients with 183 UIA. There were 115 women and 49 men with a mean age of 46 years. Embolization was successful in all patients. Procedural morbidity and mortality rates were 2.2% and 0% respectively. Immediate anatomical outcome included 54 complete occlusion (29.5%), 43 neck remnants (23.5%) and 86 incomplete occlusions (47%). Imaging follow-up was available in 137 patients (mean=26 months, range 3 to 99 months) and it showed 104 complete occlusions (75.9%), 23 neck remnants (16.8%) and 10 incomplete occlusions (7.3%). At follow-up, only 3 patients developed a significant intrastent stenosis, one of which was induced by radiosurgery. One of these patients had a symptomatic thrombo-embolic complication 3 years after stent placement. CONCLUSION: SAC of complex UIA is effective and associated with low complication rates. Even if immediate anatomical results are relatively unsatisfying, mid- and long-term follow-up show a major improvement with a high rate of adequate occlusion that is stable over time. Moreover, the long-term clinical and angiographic tolerance of intracranial stents is excellent.

Enhancing refinery heavy oil fractions analytical performance through real-time predicative modeling.

This study introduces a suite of robust models aimed to advance the determination of physiochemical properties in heavy oil refinery fractions. By integrating real-time analytical technique inside the refinery analysis, we have developed a single analyzer capable of employing six partial least square regression equations. These designed models enable to provide real-time prediction of critical petroleum properties, such as sulfur content, micro carbon residues (MCR), asphaltene content, heating value, and the concentrations of nickel and vanadium metals. Specifically tailored for heavy oil in refinery feeds with an American petroleum institute (API) gravity range of 3° to 32° and sulfur content of 2.8 to 5.5 wt%, the models streamline the analysis process within refinery operations, bridging the gap between catalytic and non-catalytic processes across refinery units. The accuracy of our physiochemical prediction models has been validated against American Society for Testing and Materials (ASTM) standards, demonstrating their capability to deliver precise real-time property values. This approach not only enhances the efficiency of refinery analysis but also sets a new standard for the monitoring and optimization of heavy oil processing in real-time approach.

Steam catalytic cracking and lump kinetics of naphtha to light olefins over nanocrystalline ZSM-5 zeolite.

This study investigates the reaction pathways and kinetics to comprehend the catalytic cracking of dodecane, a heavy naphtha model compound, over the nanocrystalline ZSM-5 catalyst in the presence and absence of steam with the aim of increasing olefin production. The nanocrystalline zeolite was characterized using XRD and BET, and the surface acidity was measured by NH3-TPD and Py-FTIR. The steam treated ZSM-5 contributed to an increase in pore volume with extra-framework alumina, resulting in highly catalytic active sites and hence higher olefin selectivity. The high conversion of dodecane (>90%) was achieved during catalytic cracking in the presence and absence of steam. In the presence of steam, the short pores of nano ZSM-5 led to an increase in the naphtha-to-olefin conversion with lesser dry gas and coke formation. The activation energies of primary cracking in the presence and absence of steam were slightly different. Lower activation energies through secondary cracking routes and higher reaction rate constants were obtained via assisted-steam catalytic cracking, promoted the selectivity towards light olefin products. Meanwhile the hydrogenation and alkylation reactions toward LPG and C5+ were favored in the absence of steam. Moreover, the ZSM-5 nano zeolite pores promoted more ß-scission reactions, resulting in higher selectivity towards ethylene and dry gas.

Catalytic conversion of heavy naphtha to reformate over the phosphorus-ZSM-5 catalyst at a lower reforming temperature.

Naphtha reforming to aromatics, naphthenes, and iso-paraffins is an essential process to increase the octane number of gasoline through the utilization of middle naphtha (whole). A ZSM-5 zeolite catalyst with modified medium pores was developed to comprehend the existing limitation of catalytic reforming to the unutilized refinery feedstock of heavy naphtha. The study applied a lower reforming conversion temperature (350 °C) than a conventional reformer without noble metal addition in an effort to lower the carbon footprint of the process and catalyst cost. The modified zeolite catalyst was impregnated with phosphorus oxide and spray-dried, followed by a hydrothermal treatment with steam. The parent and modified catalysts were characterized by NH3-TPD, SEM, XRD, NMR, FTIR, and N2 physisorption. Steam treatment was conducted to reduce the original zeolite acidity, mainly in the form of Brønsted acid sites, which resulted in the formation of phosphorus-aluminum species in the framework. The modified catalyst consisting of 40% ZSM-5 and 60% binder delivered high conversion of dodecane, and the reforming reaction selectivity favored the formation of carbonium ions through ß-scission. Therefore, monomolecular cracking took place, resulting in the production of olefins and paraffin alongside iso-paraffins, aromatics, and naphthenes, which are associated with the bimolecular pathway. The reforming of heavy naphtha was different; the free radicals from ß-scission were affected by the surrounding molecules of feedstock, and the bimolecular reactions were more dominant through zeolite pores. The study demonstrated that the addition of 10% steam during the reaction of heavy naphtha suppressed coke formation. Furthermore, high conversion and steady selectivity were maintained during the reaction, which resulted in gasoline reformate with a high research octane number (RON).

Follow-up of intracranial aneurysms treated by a WEB flow disrupter: a comparative study of DSA and contrast-enhanced MR angiography.

OBJECTIVE: To compare contrast-enhanced MR angiography (CE-MRA) and DSA for the follow-up of intracranial aneurysms (IAs) treated with the Woven EndoBridge embolization system DL (WEB DL; Sequent Medical, Aliso Viejo, California, USA). MATERIALS AND METHODS: We retrospectively identified all patients treated with a WEB DL between November 2010 and February 2013 in 2 hospitals. The IA occlusion was graded on follow-up CE-MRA and DSA by 4 independent readers and by 2 readers reaching a consensus, respectively. Interobserver agreement for MRA and intertechnique agreement was evaluated by calculating linear weighted κ. RESULTS: Fifteen patients with 16 IAs were included. Mean delay between MRA and DSA was 2 months (range 0-16 months). Interobserver agreement for MRA was substantial to almost perfect (κ=0.686-0.921; mean κ=0.809). Intertechnique agreement was moderate to substantial (κ=0.579-0.724; mean κ=0.669). Only three out of five inadequately occluded IAs were detected by MRA. CONCLUSIONS: CE-MRA is a useful tool for the follow-up of IAs treated with a WEB DL. However, early follow-up with DSA remains mandatory to detect inadequately occluded IAs.

[Pathology of small cerebral arteries demonstrated by MRI: a marker of aging?]. / Pathologie des petites artères cérébrales mise en évidence par l'IRM: un marqueur du vieillissement ?

Brain magnetic resonance imaging frequently identifies signal abnormalities in the white matter and cerebral cortex in the elderly. They are related to a degenerative disease of the small vessels that may be of ischemic (leukoaraiosis, lacunae and infarct) or hemorrhagic (microbleeds and hematomas) origin. These lesions are part of the aging process, and compounded by vascular risk factors. They increase the occurrence frequency and severity of ischemic or hemorrhagic stroke. Their importance is also associated with the presence of cognitive and/or affective symptoms, and their impact on the occurrence and evolution of dementia remains to be evaluated. The visible consequences of this microangiopathy on MRI probably represent the focal mark of a widespread cerebrovascular disease in the brain parenchyma.