Flow Field Analysis Inside and at the Outlet of the Abrasive Head

This paper focuses on the investigation of a multiphase flow of water, air, and abrasive particles inside and at the outlet of the abrasive head with the help of computational fluid dynamics calculations and measurements. A standard abrasive head with a water nozzle hole diameter of 0.33 mm (0.013”) and an abrasive nozzle cylindrical hole diameter of 1.02 mm (0.04”) were used for numerical modelling and practical testing. The computed tomography provided an exact 3D geometrical model of the cutting head that was used for the creation of the model. Velocity fields of abrasive particles at the outlet of the abrasive head were measured and analysed using particle tracking velocimetry and, consequently, compared with the calculated results. The calculation model took the distribution of the abrasive particle diameters with the help of the Rosin-Rammler function in intervals of diameters from 150 to 400 mm. In the present study, four levels of water pressure (105, 194, 302, 406 MPa) and four levels of abrasive mass flow rate (100, 200, 300, 400 kg/min) were combined. The values of water pressures and hydraulic powers measured at the abrasive head inlet were used as boundary conditions for numerical modelling. The hydraulic characteristics of the water jet were created from the measured and calculated data. The calculated pressure distribution in the cylindrical part of the abrasive nozzle was compared with studies by other authors. The details of the experiments and calculations are presented in this paper

Mechanical thrombectomy performed in thrombosed fusiform aneurysm after surgery for craniopharyngioma in adult

Introduction. Fusiform dilatation of the internal carotid artery (ICA) is reported as a possible complication of craniopharyngioma resection in childhood. Here, the authors describe such a complication in an adult patient who presented with acute symptomatic thrombosis 7 months after surgery. Materials and Methods. A 45-year-old woman presented with left hemispheric stroke due to a thrombotic supraclinoid occlusion of the terminal ICA (so called "T" occlusion). Successful revascularisation was achieved with mechanical thrombectomy. Beside recanalization of the M1 middle cerebral artery segment and ICA, an irregular filling of the fusiform aneurysm of the communicating segment of the left ICA was observed. The patient recovered after mechanical thrombectomy with no clinical sequelae. Due to the persistent filling of the aneurysm sac, a flow diverter stent was deployed across the diseased vessel segment two weeks later. The patient underwent resection of the craniopharyngioma from ipsilateral pterional craniotomy 7 months ago. Five years later the patient works full time as a nurse with no regrowth of the craniopharyngioma and no aneurysm reperfusion. Results. This case, together with four other previously reported cases, documents that fusiform aneurysm as a complication of the craniopharygioma resection is not restricted to the childhood population but may also rarely occur in adults. As the patient suffered from acute symptomatic thrombosis which required treatment under the protocol for acute large vessel occlusions, we decided to treat the aneurysm with the flow diverter stent

Imaging Methods Applicable in the Diagnostics of Alzheimer’s Disease, Considering the Involvement of Insulin Resistance

Alzheimer’s disease (AD) is an incurable neurodegenerative disease and the most frequently diagnosed type of dementia, characterized by (1) perturbed cerebral perfusion, vasculature, and cortical metabolism; (2) induced proinflammatory processes; and (3) the aggregation of amyloid beta and hyperphosphorylated Tau proteins. Subclinical AD changes are commonly detectable by using radiological and nuclear neuroimaging methods such as magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET), and single-photon emission computed tomography (SPECT). Furthermore, other valuable modalities exist (in particular, structural volumetric, diffusion, perfusion, functional, and metabolic magnetic resonance methods) that can advance the diagnostic algorithm of AD and our understanding of its pathogenesis. Recently, new insights into AD pathoetiology revealed that deranged insulin homeostasis in the brain may play a role in the onset and progression of the disease. AD-related brain insulin resistance is closely linked to systemic insulin homeostasis disorders caused by pancreas and/or liver dysfunction. Indeed, in recent studies, linkages between the development and onset of AD and the liver and/or pancreas have been established. Aside from standard radiological and nuclear neuroimaging methods and clinically fewer common methods of magnetic resonance, this article also discusses the use of new suggestive non-neuronal imaging modalities to assess AD-associated structural changes in the liver and pancreas. Studying these changes might be of great clinical importance because of their possible involvement in AD pathogenesis during the prodromal phase of the disease

The association of transradial access and transfemoral access with procedural outcomes in acute ischemic stroke patients receiving endovascular thrombectomy: A meta-analysis

Objective: There is an ongoing debate regarding the benefits of using transradial access (TRA) over transfemoral access (TFA) in endovascular therapies including endovascular thrombectomy (EVT) for acute ischemic stroke (AIS) patients. This study sought to investigate the association of TRA and TFA with procedural success, access- site complications, first-pass reperfusion (FPR), puncture-to-recanalisation (PTR) time and hemorrhagic trans- formation (HT) by performing a meta-analysis. Materials and methods: PubMed, EMBASE and Scopus were searched. Studies with patients aged ≥ 18 years and head-to-head TRA vs TFA comparisons were included. Random-effects modeling was performed to obtain summary effects and forest plots were plotted to study the association of TFA with access site complications, FPR, HT, PTR time and procedural success. Results: Six studies encompassing 945 patients (347 TRA and 598 TFA) were included in the meta-analysis. Meta- analysis revealed that in AIS patients receiving EVT, TRA was significantly associated with a decreased risk of access-site complications (RR 0.17, 95% CI 0.05 0.54; p = 0.003, z = 2.957) and HT (RR 0.07, 95% CI 0.02 0.27; p < 0.0001, z = 3.8841). However, TRA was not significantly associated with procedural success (RR 20.96, 95% CI 0.90 1.01; p = 0.141, z = 1.473), FPR (RR 0.91, 95% CI 0.79 1.05; p = 0.194, z = 1.299) and PTR time (SMD 0.14, 95% CI 0.42 0.14; p = 0.323, z = 0.989). Conclusion: Our meta-analysis demonstrated that TRA is a safe alternative to TFA, in AIS patients receiving EVT, with significantly decreased access-site complications and HT with TRA, albeit with comparable procedural success, FPR and PTR time to TFA

Thrombectomy for secondary distal, medium vessel occlusions of the posterior circulation: seeking complete reperfusion

Background Whether to approach distal occlusions endovascularly or not in medium-sized vessels secondary to proximal large vessel occlusion stroke remains unanswered. Objective To investigates the technical feasibility and safety of thrombectomy for secondary posterior circulation distal, medium vessel occlusions (DMVO). Methods TOPMOST (Treatment fOr Primary Medium vessel Occlusion STroke) is an international, retrospective, multicenter, observational registry of patients treated for distal cerebral artery occlusions. This study subanalysis endovascularly treated occlusions of the posterior cerebral artery in the P2 and P3 segment secondary preprocedural or periprocedural thrombus migration between January 2014 and June 2020. Technical feasibility was evaluated with the modified Thrombolysis in Cerebral Infarction (mTICI) scale. Procedural safety was assessed by the occurrence of symptomatic intracranial hemorrhage (sICH) and intervention-related serious adverse events. Results Among 71 patients with secondary posterior circulation DMVO who met the inclusion criteria, occlusions were present in 80.3% (57/71) located in the P2 segment and in 19.7% (14/71) in the P3 segment. Periprocedural migration occurred in 54.9% (39/71) and preprocedural migration in 45.1% (32/71) of cases. The first reperfusion attempt led in 38% (27/71) of all cases to mTICI 3. On multivariable logistic regression analysis, increased numbers of reperfusion attempts (adjusted odds ratio (aOR)=0.39, 95% CI 0.29 to 0.88, p=0.009) and preprocedural migration (aOR=4.70, 95% CI,1.35 to 16.35, p=0.015) were significantly associated with mTICI 3. sICH occurred in 2.8% (2/71). Conclusion Thrombectomy for secondary posterior circulation DMVO seems to be safe and technically feasible. Even though thrombi that have migrated preprocedurally may be easier to retract, successful reperfusion can be achieved in the majority of patients with secondary DMVO of the P2 and P3 segment

Thrombectomy for secondary distal, medium vessel occlusions of the posterior circulation: seeking complete reperfusion

Background Whether to approach distal occlusions endovascularly or not in medium-sized vessels secondary to proximal large vessel occlusion stroke remains unanswered. Objective To investigates the technical feasibility and safety of thrombectomy for secondary posterior circulation distal, medium vessel occlusions (DMVO). Methods TOPMOST (Treatment fOr Primary Medium vessel Occlusion STroke) is an international, retrospective, multicenter, observational registry of patients treated for distal cerebral artery occlusions. This study subanalysis endovascularly treated occlusions of the posterior cerebral artery in the P2 and P3 segment secondary preprocedural or periprocedural thrombus migration between January 2014 and June 2020. Technical feasibility was evaluated with the modified Thrombolysis in Cerebral Infarction (mTICI) scale. Procedural safety was assessed by the occurrence of symptomatic intracranial hemorrhage (sICH) and intervention-related serious adverse events. Results Among 71 patients with secondary posterior circulation DMVO who met the inclusion criteria, occlusions were present in 80.3% (57/71) located in the P2 segment and in 19.7% (14/71) in the P3 segment. Periprocedural migration occurred in 54.9% (39/71) and preprocedural migration in 45.1% (32/71) of cases. The first reperfusion attempt led in 38% (27/71) of all cases to mTICI 3. On multivariable logistic regression analysis, increased numbers of reperfusion attempts (adjusted odds ratio (aOR)=0.39, 95% CI 0.29 to 0.88, p=0.009) and preprocedural migration (aOR=4.70, 95% CI,1.35 to 16.35, p=0.015) were significantly associated with mTICI 3. sICH occurred in 2.8% (2/71). Conclusion Thrombectomy for secondary posterior circulation DMVO seems to be safe and technically feasible. Even though thrombi that have migrated preprocedurally may be easier to retract, successful reperfusion can be achieved in the majority of patients with secondary DMVO of the P2 and P3 segment