The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform
Loic Panh - One of the best experts on this subject based on the ideXlab platform.
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early detection of subclinical left ventricular dysfunction after breast cancer radiation therapy using speckle tracking echocardiography association between cardiac exposure and longitudinal Strain Reduction baccarat study
Radiation Oncology, 2019Co-Authors: V Walker, Olivier Lairez, Olivier Fondard, Atul Pathak, Baptiste Pinel, Christian Chevelle, D Franck, Gaelle Jimenez, J Camilleri, Loic PanhAbstract:Breast cancer (BC) radiotherapy (RT) can induce cardiotoxicity, with adverse events often observed many years after BC RT. Subclinical left ventricular (LV) dysfunction can be detected early after BC RT with global longitudinal Strain (GLS) measurement based on 2D speckle-tracking echocardiography. This 6-month follow-up analysis from the BACCARAT prospective study aimed to investigate the association between cardiac radiation doses and subclinical LV dysfunction based on GLS Reduction. The patient study group consisted of 79 BC patients (64 left-sided BC, 15 right-sided BC) treated with RT without chemotherapy. Echocardiographic parameters, including GLS, were measured before RT and 6 months post-RT. The association between subclinical LV dysfunction, defined as GLS Reduction > 10%, and radiation doses to whole heart and the LV were performed based on logistic regressions. Non-radiation factors associated with subclinical LV dysfunction including age, BMI, hypertension, hypercholesterolemia and endocrine therapy were considered for multivariate analyses. A mean decrease of 6% in GLS was observed (− 15.1% ± 3.2% at 6 months vs. − 16.1% ± 2.7% before RT, p = 0.01). For left-sided patients, mean heart and LV doses were 3.1 ± 1.3 Gy and 6.7 ± 3.4 Gy respectively. For right-sided patients, mean heart dose was 0.7 ± 0.5 Gy and median LV dose was 0.1 Gy. Associations between GLS Reduction > 10% (37 patients) and mean doses to the heart and the LV as well as the V20 were observed in univariate analysis (Odds Ratio = 1.37[1.01–1.86], p = 0.04 for Dmean Heart; OR = 1.14 [1.01–1.28], p = 0.03 for Dmean LV; OR = 1.08 [1.01–1.14], p = 0.02 for LV V20). In multivariate analysis, these associations did not remain significant after adjustment for non-radiation factors. Further exploratory analysis allowed identifying a subgroup of patients (LV V20 > 15%) for whom a significant association with subclinical LV dysfunction was found (adjusted OR = 3.97 [1.01–15.70], p = 0.048). This analysis indicated that subclinical LV dysfunction defined as a GLS decrease > 10% is associated with cardiac doses, but adjustment for non-radiation factors such as endocrine therapy lead to no longer statistically significant relationships. However, LV dosimetry may be promising to identify high-risk subpopulations. Larger and longer follow-up studies are required to further investigate these associations. ClinicalTrials.gov: NCT02605512, Registered 6 November 2015 - Retrospectively registered
George Z. Voyiadjis - One of the best experts on this subject based on the ideXlab platform.
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studying the effect of a hydrostatic stress Strain Reduction factor on damage mechanics of concrete materials
Journal of the mechanical behavior of materials, 2013Co-Authors: Ziad N. Taqieddin, George Z. VoyiadjisAbstract:In the Nonlinear Finite Element Analysis (NFEA) of concrete materials, Continuum Damage Mechanics (CDM) provide a powerful framework for the derivation of constitutive models capable of describing the mechanical behavior of such materials. The internal state variables of CDM can be introduced to the elastic analysis of concrete to form elastic-damage models (no inelastic Strains), or to the elastic-plastic analysis in order to form coupled/uncoupled elastic-plastic-damage models. Experimental evidence that is well documented in literature shows that concrete’s susceptibility to damage and failure is distinguished under deviatoric loading from that corresponding to hydrostatic loading. A Reduction factor is usually introduced into a CDM model to reduce the susceptibility of concrete to hydrostatic stresses/Strains. In this work, the effect of a hydrostatic stress Reduction factor on the performances of two NFEA concrete models will be studied. These (independently published) models did not provide any results showing such effect. One of these two models is an elastic-damage model while the other is an uncoupled elastic-plastic-damage model. Comparisons are carried out between the performances of the two models under tensile and compressive loadings, clearly showing the effect of the Reduction factor on the numerically depicted behaviors of concrete materials. In order to have rational comparisons, the hydrostatic stress Reduction factor applied to each model is chosen to be a function of the internal state variables common to both models. Therefore, once the two models are calibrated to simulate the experimental behaviors, their corresponding Reduction factors are readily available at every increment of the iterative NFEA procedures.
Thomas P. Vail - One of the best experts on this subject based on the ideXlab platform.
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position of hip resurfacing component affects Strain and resistance to fracture in the femoral neck
Journal of Bone and Joint Surgery American Volume, 2008Co-Authors: Thomas P. Vail, Richard R. Glisson, David E Dominguez, Kenichi Kitaoka, Danielle OttavianoAbstract:Background: Retrieval studies have suggested that the cause of femoral implant failure after metal-on-metal hip resurfacing is multifactorial. Both varus positioning of the femoral component and notching of the superior part of the femoral neck have been associated with femoral component failure. The hypotheses of this study were that placement of a femoral resurfacing component alters femoral neck loading and that the cortical Strain pattern reflecting this loading is directly related to the spatial orientation of the resurfacing component. An additional hypothesis was that notching of the superior part of the neck during implantation results in a decreased resistance to neck fracture under axial loading. Methods: Varus, anteverted, retroverted, and anatomic positions of the femoral component were tested in sixty-four cadaveric femora. Simulated stance-phase loading was applied, and the shear Strain on the femoral neck cortex was quantified with use of a photoelastic method. Preimplantation and postimplantation Strain levels were compared over the entire neck region with use of generalized estimating equations. The influence of anteversion and retroversion of the component and notching of the superior part of the neck on the neck strength were evaluated. Results: Placement of the implant in 10° of varus alignment relative to anatomic positioning increased Strain on the superior aspect of the neck by 19% to 23% compared with intact femora. Anteverted and retroverted placement of the implant produced elevated Strain in the anterior-inferior and posterior-inferior aspects of the neck, respectively. Placement of the component stem in alignment with the anatomic neck axis decreased neck cortical Strain 6% to 19% compared with intact femora. Notching of the superior aspect of the neck decreased neck strength by 21%. Conclusions: Relatively small deviations from anatomic alignment of a resurfacing hip component result in marked localized increases in loading of the femoral neck under conditions approximating single-limb stance. Neutral positioning of the femoral component results in localized Strain Reduction. Notching of the superior aspect of the femoral neck significantly reduces the resistance to fracture (p = 0.008). Clinical Relevance: The implantation-related changes observed in this analysis might be used to model the initial loading conditions in the femoral neck after resurfacing and may serve to validate finite element analysis predictions and clinical observations.
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The effect of hip stem material modulus on surface Strain in human femora.
Journal of Biomechanics, 1998Co-Authors: Thomas P. Vail, Richard R. Glisson, Theodosios D. Koukoubis, Farshid GuilakAbstract:Human femora were used to compare the changes in bone surface Strain resulting from decreasing the material modulus of a collarless hip stem to determine whether a highly elastic stem increased bone loading. Three substrate materials were tested: titanium (modulus of elasticity 110 GPa), carbon fiber composite (modulus of elasticity 52 GPa), and polymethylmethacrylate (PMMA, modulus of elasticity of 1.9 GPa). Two separate analyses were performed in which femora were implanted randomly with one of the three stem types. Results showed that assembly Strains did not differ significantly among different materials. There was a large Strain Reduction in the proximal region of the femora for all stem substrates relative to the intact femur. Although there was statistically greater surface shear Strain as the material modulus decreased, the PMMA stem did not substantially increase bone loading.
L Hee - One of the best experts on this subject based on the ideXlab platform.
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subclinical cardiac dysfunction detected by Strain imaging during breast irradiation with persistent changes 6 weeks after treatment
International Journal of Radiation Oncology Biology Physics, 2015Co-Authors: L Hee, Vikneswary Batumalai, Christine Allman, Peter S Macdonald, G Delaney, D LonerganAbstract:Purpose To evaluate 2-dimensional Strain imaging (SI) for the detection of subclinical myocardial dysfunction during and after radiation therapy (RT). Methods and Materials Forty women with left-sided breast cancer, undergoing only adjuvant RT to the left chest, were prospectively recruited. Standard echocardiography and SI were performed at baseline, during RT, and 6 weeks after RT. Strain (S) and Strain rate (Sr) parameters were measured in the longitudinal, circumferential, and radial planes. Correlation of change in global longitudinal Strain (GLS % and Δ change) and the volume of heart receiving 30 Gy (V30) and mean heart dose (MHD) were examined. Results Left ventricular ejection fraction was unchanged; however, longitudinal systolic S and Sr and radial S were significantly reduced during RT and remained reduced at 6 weeks after treatment [longitudinal S (%) −20.44 ± 2.66 baseline vs −18.60 ± 2.70* during RT vs −18.34 ± 2.86* at 6 weeks after RT; longitudinal Sr (s −1 ) −1.19 ± 0.21 vs −1.06 ± 0.18* vs −1.06 ± 0.16*; radial S (%) 56.66 ± 18.57 vs 46.93 ± 14.56* vs 49.22 ± 15.81*; * P −1 ) 1.47 ± 0.32 vs 1.29 ± 0.27*; longitudinal A Sr (s −1 ) 1.19 ± 0.31 vs 1.03 ± 0.24*; * P P =.05; GLS % change and V30 ρ = 0.288, P =.076; GLS Δ change and MHD ρ = 0.348, P =.03; GLS % change and MHD ρ = 0.346, P =.031). Conclusions Subclinical myocardial dysfunction was detected by 2-dimensional SI during RT, with changes persisting 6 weeks after treatment, though long-term effects remain unknown. Additionally, a modest correlation between Strain Reduction and radiation dose was observed.
Dor Amram - One of the best experts on this subject based on the ideXlab platform.
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coherency Strain Reduction in particles on a substrate as a driving force for solute segregation
Scripta Materialia, 2016Co-Authors: Eugen Rabkin, Dor Amram, David Barlam, Roni Z ShneckAbstract:Abstract It is well-established that solute segregation to interfaces is driven by the Reduction of their energy. Here we propose coherency Strain energy Reduction due to lattice misfit modification at an interphase boundary, as a distinct driving force for segregation. Our experiments with Fe-Au particles on a sapphire substrate, together with finite element method calculations demonstrated that the elastic energy contribution to the total driving force for Au segregation exceeds its interfacial energy counterpart for particles larger than ~ 10 nm in size.
