ORCID Profile
0000-0002-2641-6384
Current Organisation
Universitat Politècnica de Catalunya
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Publisher: Wiley
Date: 12-2017
Publisher: Springer Science and Business Media LLC
Date: 04-08-2020
DOI: 10.1007/S00466-020-01884-4
Abstract: The scaled boundary finite element method (SBFEM) has recently been employed as an efficient tool to model three-dimensional structures, in particular when the geometry is provided as a voxel-based image. To this end, an octree decomposition of the computational domain is deployed, and each cubic cell is treated as an SBFE subdomain. The surfaces of each subdomain are discretized in the finite element sense. We improve on this idea by combining the semi-analytical concept of the SBFEM with a particular class of transition elements on the subdomains’ surfaces. Thus, a triangulation of these surfaces as executed in previous works is avoided, and consequently, the number of surface elements and degrees of freedom is reduced. In addition, these discretizations allow coupling elements of arbitrary order such that local p -refinement can be achieved straightforwardly.
Publisher: Elsevier BV
Date: 08-2014
Publisher: Acoustical Society of America (ASA)
Date: 03-2014
DOI: 10.1121/1.4864303
Abstract: In this paper a numerical approach is presented to compute dispersion curves for solid waveguides coupled to an infinite medium. The derivation is based on the scaled boundary finite element method that has been developed previously for waveguides with stress-free surfaces. The effect of the surrounding medium is accounted for by introducing a dashpot boundary condition at the interface between the waveguide and the adjoining medium. The d ing coefficients are derived from the acoustic impedances of the surrounding medium. Results are validated using an improved implementation of an absorbing region. Since no discretization of the surrounding medium is required for the dashpot approach, the required number of degrees of freedom is typically 10 to 50 times smaller compared to the absorbing region. When compared to other finite element based results presented in the literature, the number of degrees of freedom can be reduced by as much as a factor of 4000.
Publisher: Wiley
Date: 12-2018
Publisher: IEEE
Date: 10-2012
Publisher: Elsevier BV
Date: 08-2015
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2020
DOI: 10.1161/STROKEAHA.120.030157
Abstract: In patients undergoing mechanical thrombectomy, achieving complete (Thrombolysis in Cerebral Infarction 3) rather than incomplete successful reperfusion (Thrombolysis in Cerebral Infarction 2b) is associated with better functional outcome. Despite technical improvements, incomplete reperfusion remains the final angiographic result in 40% of patients according to recent trials. As most incomplete reperfusions are caused by distal vessel occlusions, they are potentially amenable to rescue strategies. While observational data suggest a net benefit of up to 20% in functional independence of incomplete versus complete reperfusions, the net benefit of secondary improvement from Thrombolysis in Cerebral Infarction 2b to 3 reperfusion might differ due to lengthier procedures and delayed reperfusion. Current strategies to tackle distal vessel occlusions consist of distal (microcatheter) aspiration, small adjustable stent retrievers, and administration of intra-arterial thrombolytics. While there are promising reports evaluating those techniques, all available studies show relevant limitations in terms of selection bias, single-center design, or nonconsecutive patient inclusion. Besides an assessment of risks associated with rescue maneuvers, we advocate that the decision-making process should also include a consideration of potential outcomes if complete reperfusion would successfully be achieved. These include (1) a futile angiographic improvement (hypoperfused territory is already infarcted), (2) an unnecessary angiographic improvement (the patient would not have developed infarction if no rescue maneuver was performed), and (3) a successful rescue maneuver with clinical benefit. Currently there is paucity of data on how these scenarios can be predicted and the decision whether to treat or to stop in a patient with incomplete reperfusion involves many unknowns. To advance the status quo, we outline current knowledge gaps and avenues of potential research regarding this clinically important question.
Publisher: Elsevier BV
Date: 07-2014
DOI: 10.1016/J.ULTRAS.2014.02.004
Abstract: This paper addresses the computation of dispersion curves and mode shapes of elastic guided waves in axisymmetric waveguides. The approach is based on a Scaled Boundary Finite Element formulation, that has previously been presented for plate structures and general three-dimensional waveguides with complex cross-section. The formulation leads to a Hamiltonian eigenvalue problem for the computation of wavenumbers and displacement litudes, that can be solved very efficiently. In the axisymmetric representation, only the radial direction in a cylindrical coordinate system has to be discretized, while the circumferential direction as well as the direction of propagation are described analytically. It is demonstrated, how the computational costs can drastically be reduced by employing spectral elements of extremely high order. Additionally, an alternative formulation is presented, that leads to real coefficient matrices. It is discussed, how these two approaches affect the computational efficiency, depending on the elasticity matrix. In the case of solid cylinders, the singularity of the governing equations that occurs in the center of the cross-section is avoided by changing the quadrature scheme. Numerical ex les show the applicability of the approach to homogeneous as well as layered structures with isotropic or anisotropic material behavior.
Publisher: Wiley
Date: 17-11-2017
DOI: 10.1002/NME.5445
Publisher: Springer Science and Business Media LLC
Date: 02-06-2017
Publisher: Elsevier BV
Date: 06-2019
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 09-2021
DOI: 10.1161/STROKEAHA.120.032935
Abstract: Benefit of early endovascular treatment (EVT) for ischemic stroke varies considerably among patients. The MR PREDICTS decision tool, derived from MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands), predicts outcome and treatment benefit based on baseline characteristics. Our aim was to externally validate and update MR PREDICTS with data from international trials and daily clinical practice. We used in idual patient data from 6 randomized controlled trials within the HERMES (Highly Effective Reperfusion Evaluated in Multiple Endovascular Stroke Trials) collaboration to validate the original model. Then, we updated the model and performed a second validation with data from the observational MR CLEAN Registry. Primary outcome was functional independence (defined as modified Rankin Scale score 0–2) 3 months after stroke. Treatment benefit was defined as the difference between the probability of functional independence with and without EVT. Discriminative performance was evaluated using a concordance (C ) statistic. We included 1242 patients from HERMES (633 assigned to EVT, 609 assigned to control) and 3156 patients from the MR CLEAN Registry (all of whom underwent EVT within 6.5 hours). The C -statistic for functional independence was 0.74 (95% CI, 0.72–0.77) in HERMES and, after model updating, 0.80 (0.78–0.82) in the Registry. Median predicted treatment benefit of routinely treated patients (Registry) was 10.3% (interquartile range, 5.8%–14.4%). Patients with low ( %) predicted treatment benefit (n=135/3156 [4.3%]) had low rates of functional independence, irrespective of reperfusion status, suggesting potential absence of treatment benefit. The updated model was made available online for clinicians and researchers at www.mrpredicts.com . Because of the substantial treatment effect and small potential harm of EVT, most patients arriving within 6 hours at an endovascular-capable center should be treated regardless of their clinical characteristics. MR PREDICTS can be used to support clinical judgement when there is uncertainty about the treatment indication, when resources are limited, or before a patient is to be transferred to an endovascular-capable center.
Publisher: Elsevier BV
Date: 07-2013
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 08-2019
Publisher: Acoustical Society of America (ASA)
Date: 09-2012
DOI: 10.1121/1.4740478
Abstract: The scaled boundary finite element method is applied to the simulation of Lamb waves for ultrasonic testing applications. With this method, the general elastodynamic problem is solved, while only the boundary of the domain under consideration has to be discretized. The reflection of the fundamental Lamb wave modes from cracks of different geometry in a steel plate is modeled. A test problem is compared with commercial finite element software, showing the efficiency and convergence of the scaled boundary finite element method. A special formulation of this method is utilized to calculate dispersion relations for plate structures. For the discretization of the boundary, higher-order elements are employed to improve the efficiency of the simulations. The simplicity of mesh generation of a cracked plate for a scaled boundary finite element analysis is illustrated.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2022
DOI: 10.1161/STROKEAHA.122.039774
Abstract: Age and infarct volume are strong predictors of outcome in patients with ischemic stroke who underwent endovascular therapy (EVT). We aimed to investigate the impact of ischemic core volume (ICV) on stroke outcome after EVT in elderly. Using the HERMES (Highly Effective Reperfusion Using Multiple Endovascular Devices) collaboration, a patient-level meta-analysis of 7 randomized trials in which patients were enrolled from December 2010 to April 2015) dataset, we categorized patients into those aged and ≥75 years. ICV was calculated on computed tomography perfusion or magnetic resonance diffusion-weighted imaging. The association between ICV and the benefit of EVT over best medical treatment on outcome (modified Rankin Scale [mRS] at 90 days) and an ICV threshold for high likelihood (≥90%) of very poor outcome (mRS score ≥5) after EVT were investigated. A total of 899 patients who had baseline ICV data, 247 patients aged ≥75 years, of which 118 were randomized in the EVT arm. Patients aged ≥75 years required smaller ICV to achieve mRS score ≤3 than those aged years in the EVT arm (median 10.7 mL versus 23.9 mL, P .001). In patients aged ≥75 years, modeling of outcome in both treatment arms revealed potential loss of effect for EVT at ICV of ≥50 mL or ≥85 mL for achieving mRS score ≤3 or ≤4, respectively. Treatment effect of EVT was significant in ICV mL for mRS ≤3 (odds ratio 2.38, 95% confidence interval 1.35–4.22). ICV ≥132 mL was a threshold for high likelihood of very poor outcome after EVT. However, EVT still predicted at least 30% rate of mRS ≤3 at 150 mL ICV if near-complete or complete reperfusion was achieved. Baseline ICV has an impact on stroke outcome after EVT in the elderly, but elderly patients with large ICV may still benefit from EVT if near-complete or complete reperfusion is achieved. Young patients seem to benefit from EVT regardless of ICV status.
Publisher: SAGE Publications
Date: 24-08-2022
DOI: 10.1177/17474930221120345
Abstract: Uncertainty exists over the optimal level of blood pressure (BP) after mechanical thrombectomy (MT) for acute ischemic stroke (AIS). We aim to determine the effectiveness and safety of intensive BP-lowering following MT reperfusion of large-vessel occlusion (LVO)-related AIS. The second ENhanced Control of Hypertension ANd Thrombolysis strokE stuDy (ENCHANTED2) is an investigator-initiated, multicenter, prospective, randomized, open, blinded-endpoint (PROBE) trial of intensive systolic BP (SBP) control in reperfused (extended treatment in cerebral infarction (eTICI) classification 2b/2c/3) LVO-AIS patients with persistent hypertension (SBP ⩾ 140 mmHg) at 60+ sites in China, and Australia and the United Kingdom. Eligible patients are centrally randomly allocated to more- (target SBP ⩽ 120 mmHg within 1 h) or less-intensive (target SBP 140–180 mmHg) BP management, to be maintained for 72 h. Primary outcome is an ordinal shift analysis of scores on the modified Rankin scale (mRS) at 90 days. S le size of 2257 patients provides 90% power to detect a 6.5% absolute reduction in poor outcome from more-intensive BP-lowering using ordinal logistic regression. Recruitment started in China in July 2020. At a meeting of the independent Data and Safety Monitoring Board in March 2022 to review primary outcome data available for 347 patients, they recommended suspension of recruitment due to safety concerns in the more-intensive group which was implemented by the Trial Steering Committee (TSC) with 817 randomized patients only in China. The TSC then stopped recruitment after the safety concerns persisted on further review of the data in June 2022. The TSC will make a decision on restarting the trial with modification of the protocol when the results are made public. ENCHANTED2 will provide further randomized evidence on the role of intensive BP-lowering after reperfusion in MT-treated AIS patients. ClinicalTrials.gov NCT04140110 registered 25 October 2019.
Publisher: Elsevier BV
Date: 07-2021
Publisher: Elsevier BV
Date: 12-2021
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2023
DOI: 10.1161/STROKEAHA.122.042200
Abstract: Infarct in a new territory (INT) is a known complication of endovascular stroke therapy. We assessed the incidence of INT, outcomes after INT, and the impact of concurrent treatments with intravenous thrombolysis and nerinetide. Data are from ESCAPE-NA1 trial (Safety and Efficacy of Nerinetide [NA-1] in Subjects Undergoing Endovascular Thrombectomy for Stroke), a multicenter, international randomized study that assessed the efficacy of intravenous nerinetide in subjects with acute ischemic stroke who underwent endovascular thrombectomy within 12 hours from onset. Concurrent treatment and outcomes were collected as part of the trial protocol. INTs were identified on core lab imaging review of follow-up brain imaging and defined by the presence of infarct in a new vascular territory, outside the baseline target occlusion(s) on follow-up brain imaging (computed tomography or magnetic resonance imaging). INTs were classified by maximum diameter ( , 2–20, and mm), number, and location. The association between INT and clinical outcomes (modified Rankin Scale and death) was assessed using standard descriptive techniques and adjusted estimates of effect were derived from Poisson regression models. Among 1092 patients, 103 had INT (9.3%, median age 69.5 years, 49.5% females). There were no differences in baseline characteristics between those with versus without INT. Most INTs (91/103, 88.3%) were not associated with visible occlusions on angiography and 39 out of 103 (37.8%) were mm in maximal diameter. The most common INT territory was the anterior cerebral artery (27.8%). Almost half of the INTs were multiple (46 subjects, 43.5%, range, 2–12). INT was associated with poorer outcomes as compared to no INT on the primary outcome of modified Rankin Scale score of 0 to 2 at 90 days (adjusted risk ratio, 0.71 [95% CI, 0.57–0.89]). Infarct volume in those with INT was greater by a median of 21 cc compared with those without, and there was a greater risk of death as compared to patients with no INT (adjusted risk ratio, 2.15 [95% CI, 1.48–3.13]). Infarcts in a new territory are common in in iduals undergoing endovascular thrombectomy for acute ischemic stroke and are associated with poorer outcomes. Optimal therapeutic approaches, including technical strategies, to reduce INT represent a new target for incremental quality improvement of endovascular thrombectomy. URL: www.clinicaltrials.gov Unique identifier: NCT02930018.
Publisher: Elsevier BV
Date: 12-2021
Publisher: Elsevier BV
Date: 12-2015
Publisher: Elsevier BV
Date: 10-2020
Publisher: Springer Science and Business Media LLC
Date: 19-12-2019
Publisher: Trans Tech Publications, Ltd.
Date: 09-2013
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.778.303
Abstract: Timber poles are commonly used for telecommunication and power distribution networks, wharves or jetties, piling or as a substructure of short span bridges. Most of the available techniques currently used for non-destructive testing (NDT) of timber structures are based on one-dimensional wave theory. If it is essential to detect small sized damage, it becomes necessary to consider guided wave (GW) propagation as the behaviour of different propagating modes cannot be represented by one-dimensional approximations. However, due to the orthotropic material properties of timber, the modelling of guided waves can be complex. No analytical solution can be found for plotting dispersion curves for orthotropic thick cylindrical waveguides even though very few literatures can be found on the theory of GW for anisotropic cylindrical waveguide. In addition, purely numerical approaches are available for solving these curves. In this paper, dispersion curves for orthotropic cylinders are computed using the scaled boundary finite element method (SBFEM) and compared with an isotropic material model to indicate the importance of considering timber as an anisotropic material. Moreover, some simplification is made on orthotropic behaviour of timber to make it transversely isotropic due to the fact that, analytical approaches for transversely isotropic cylinder are widely available in the literature. Also, the applicability of considering timber as a transversely isotropic material is discussed. As an orthotropic material, most material testing results of timber found in the literature include 9 elastic constants (three elastic moduli and six Poisson's ratios), hence it is essential to select the appropriate material properties for transversely isotropic material which includes only 5 elastic constants. Therefore, comparison between orthotropic and transversely isotropic material model is also presented in this article to reveal the effect of elastic moduli and Poisson's ratios on dispersion curves. Based on this study, some suggestions are proposed on selecting the parameters from an orthotropic model to transversely isotropic condition.
Publisher: Elsevier BV
Date: 05-2012
Publisher: Elsevier BV
Date: 04-2022
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-2022
DOI: 10.1161/STROKEAHA.121.037073
Abstract: Cerebral edema after large hemispheric infarction is associated with poor functional outcome and mortality. Net water uptake (NWU) quantifies the degree of hypoattenuation on unenhanced-computed tomography (CT) and is increasingly used to measure cerebral edema in stroke research. Hemorrhagic transformation and parenchymal contrast staining after thrombectomy may confound NWU measurements. We investigated the correlation of NWU measured postthrombectomy with volumetric markers of cerebral edema and association with functional outcomes. In a pooled in idual patient level analysis of patients presenting with anterior circulation large hemispheric infarction (core 80–300 mL or Alberta Stroke Program Early CT Score ≤5) in the HERMES (Highly Effective Reperfusion Evaluated in Multiple Endovascular Stroke trials) data set, cerebral edema was defined as the volumetric expansion of the ischemic hemisphere expressed as a ratio to the contralateral hemisphere(rHV). NWU and midline-shift were compared with rHV as the reference standard on 24-hour follow-up CT, adjusted for hemorrhagic transformation and the use of thrombectomy. Association between edema markers and day 90 functional outcomes (modified Rankin Scale) was assessed using ordinal logistic regression. Overall (n=144), there was no correlation between NWU and rHV (r s =0.055, P =0.51). In sub-group analyses, a weak correlation between NWU with rHV was observed after excluding patients with any degree of hemorrhagic transformation (r s =0.211, P =0.015), which further improved after excluding thrombectomy patients (r s =0.453, P =0.001). Midline-shift correlated strongly with rHV in all sub-group analyses (r s .753, P =0.001). Functional outcome at 90 days was negatively associated with rHV (adjusted common odds ratio, 0.46 [95% CI, 0.32–0.65] P .001) and midline-shift (adjusted common odds ratio, 0.85 [95% CI, 0.78–0.92] P .001) but not NWU (adjusted common odds ratio, 1.00 [95% CI, 0.97–1.03] P =0.84), adjusted for age, baseline National Institutes of Health Stroke Scale, and thrombectomy. Prognostic performance of NWU improved after excluding patients with hemorrhagic transformation and thrombectomy (adjusted odds ratio, 0.90 [95% CI, 0.80–1.02] P =0.10). NWU correlated poorly with conventional markers of cerebral edema and was not associated with clinical outcome in the presence of hemorrhagic transformation and thrombectomy. Measuring NWU postthrombectomy requires validation before implementation into clinical research. At present, the use of NWU should be limited to baseline CT, or follow-up CT only in patients without hemorrhagic transformation or treatment with thrombectomy.
Publisher: American Society of Neuroradiology (ASNR)
Date: 30-11-2017
DOI: 10.3174/AJNR.A5462
Publisher: Elsevier BV
Date: 2014
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2022
DOI: 10.1161/STROKEAHA.122.039717
Abstract: Leptomeningeal collateral status on baseline computed tomographic angiography (CTA) is associated with clinical outcome after acute ischemic stroke treatment. However, assessment of collateral status is not uniform. To compare 3 different CTA collateral scores (CS) and imaging techniques about their association with clinical outcome. Pooled analysis of patient-level data from the Highly Effective Reperfusion Using Multiple Endovascular Devices collaboration. Patients with large vessel occlusion from 7 randomized controlled trials that compared endovascular thrombectomy with standard medical care were included. Three different CS (Tan CS, regional CS [rCS], and regional Alberta Stroke Program Early CT Score CS) and 2 imaging techniques (single-phase [sCTA] and multiphase/dynamic CTA) were evaluated. Functional independence (modified Rankin Scale score 0–2) at 3 months poststroke was the primary outcome. Furthermore, we assessed the effect of sCTA image acquisition time on collateral status assessment using an adjusted ordinal logistic regression model to obtain predicted values for the trichotomized rCS. Among 1147 pooled patients, 948 (82.7%) had sCTA and 199 (17.3%) multiphase/dynamic CTA as baseline angiography. With all 3 collateral scales, better CSs were associated with better 3-month functional outcome. With sCTA images, the rCS (area under the curve [AUC] 0.63) and regional Alberta Stroke Program Early CT Score CS (AUC 0.62) better predicted functional outcome than the Tan CS (AUC 0.60, respectively P .001 and P =0.02). With multiphase/dynamic CTA images, all collateral scales performed similarly in predicting functional outcome (rCS [AUC 0.61] regional Alberta Stroke Program Early CT Score CS [AUC 0.61] versus Tan CS [AUC 0.61], respectively P =0.93 and P =0.91). Overall, no endovascular thrombectomy treatment effect modification by collateral status (rCS) was demonstrated ( P =0.41). sCTA timing independently influenced CS assessment. On earlier timed sCTA, the predicted proportions of scans with poor collaterals was higher and vice versa. In this data set of highly selected patients with stroke, using a regional CS on sCTA likely allows for the most accurate prediction of functional outcome while on time-resolved CTA, the type of CS did not matter. Patients across all collateral grades benefit from endovascular thrombectomy. sCTA timing independently influenced CS assessment.
Publisher: AIP
Date: 2012
DOI: 10.1063/1.3703223
Publisher: Elsevier BV
Date: 04-2020
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2023
DOI: 10.1161/STROKEAHA.121.038407
Abstract: The clinical and economic benefit of endovascular treatment (EVT) in addition to best medical management in patients with stroke with mild preexisting symptoms/disability is not well studied. We aimed to investigate cost-effectiveness of EVT in patients with large vessel occlusion and mild prestroke symptoms/disability, defined as a modified Rankin Scale score of 1 or 2. Data are from the HERMES collaboration (Highly Effective Reperfusion Evaluated in Multiple Endovascular Stroke Trials), which pooled patient-level data from 7 large, randomized EVT trials. We used a decision model consisting of a short-run model to analyze costs and functional outcomes within 90 days after the index stroke and a long-run Markov state transition model (cycle length of 12 months) to estimate expected lifetime costs and outcomes from a health care and a societal perspective. Incremental cost-effectiveness ratio and net monetary benefits were calculated, and a probabilistic sensitivity analysis was performed. EVT in addition to best medical management resulted in lifetime cost savings of $2821 (health care perspective) or $5378 (societal perspective) and an increment of 1.27 quality-adjusted life years compared with best medical management alone, indicating dominance of additional EVT as a treatment strategy. The net monetary benefits were higher for EVT in addition to best medical management compared with best medical management alone both at the higher (100 000$/quality-adjusted life years) and lower (50 000$/quality-adjusted life years) willingness to pay thresholds. Probabilistic sensitivity analysis showed decreased costs and an increase in quality-adjusted life years for additional EVT compared with best medical management only. From a health-economic standpoint, EVT in addition to best medical management should be the preferred strategy in patients with acute ischemic stroke with large vessel occlusion and mild prestroke symptoms/disability.
Location: Germany
No related grants have been discovered for Hauke Gravenkamp.