The Experts below are selected from a list of 6564 Experts worldwide ranked by ideXlab platform
Pierre Aletti - One of the best experts on this subject based on the ideXlab platform.
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Predictive model of the prostate motion in the context of radiotherapy: A biomechanical approach relying on urodynamic data and mechanical testing
Journal of the mechanical behavior of biomedical materials, 2015Co-Authors: Mohamed Boubaker, Mohamed Haboussi, Jean-françois Ganghoffer, Pierre AlettiAbstract:In this paper, a biomechanical approach relying on urodynamic data and mechanical tests is proposed for an accurate prediction of the motion of the pelvic organs in the context of the prostate radiotherapy. As a first step, an experimental protocol is elaborated to characterize the mechanical properties of the bladder and rectum wall tissues; uniaxial tensile tests are performed on porcine substrates. In a second step, the parameters of Ogden-type hyperelastic constitutive models are identified; their relevance in the context of the implementation of a human biomechanical model is verified by means of preliminary Finite Elements (FE) simulations against human urodynamic data. In a third step, the identified constitutive equations are employed for the simulations of the motion and interactions of the pelvic organs due to concomitant changes of the distension volumes of the urinary bladder and rectum. The effectiveness of the developed biomechanical model is demonstrated in investigating the motion of the bladder, rectum and prostate organs; the results in terms of displacements are shown to be in good agreement with measurements inherent to a Deceased Person, with a relative error close to 6%.
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finite element simulation of interactions between pelvic organs predictive model of the prostate motion in the context of radiotherapy
Journal of Biomechanics, 2009Co-Authors: Mohamed Bader Boubaker, Jean-françois Ganghoffer, Mohamed Haboussi, Pierre AlettiAbstract:The setting up of predictive models of the pelvic organ motion and deformation may prove an efficient tool in the framework of prostate cancer radiotherapy, in order to deliver doses more accurately and efficiently to the clinical target volume (CTV). A finite element (FE) model of the prostate, rectum and bladder motion has been developed, investigating more specifically the influence of the rectum and bladder repletions on the gland motion. The required organ geometries are obtained after processing the computed tomography (CT) images, using specific softwares. Due to their structural characteristics, a 3D shell discretization is adopted for the rectum and the bladder, whereas a volume discretization is adopted for the prostate. As for the mechanical behavior modelling, first order Ogden hyperelastic constitutive laws for both the rectum and bladder are identified. The prostate is comparatively considered as more rigid and is accordingly modelled as an elastic tissue undergoing small strains. A FE model is then created, accounting for boundary and contact conditions, internal and applied loadings being selected as close as possible to available anatomic data. The order of magnitude of the prostate motion predicted by the FE simulations is similar to the measurements done on a Deceased Person, accounting for the delineation errors, with a relative error around 8%. Differences are essentially due to uncertainties in the constitutive parameters, pointing towards the need for the setting up of direct measurement of the organs mechanical behavior.
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Qualitative estimation of pelvic organ interactions and their consequences on prostate motion: Study on a Deceased Person
Medical Physics, 2006Co-Authors: Laurent Keros, Valérie Bernier, Pierre Aletti, Vincent Marchesi, Didier Wolf, Alain NoelAbstract:In an attempt to have better targeting of the prostate during radiotherapy it is necessary to understand the mechanical interactions between bladder, rectum, and prostate and estimate their consequences on prostate motion. For this, the volumes of bladder, rectum, and lungs were modified concomitantly on a Deceased Person. A CT acquisition was performed for each of these different pelvic configurations (36 acquisitions). An increase in the volume of the bladder or lungs induces a compression of tissues of the pelvic area from its supero-anterior (S-A) to infero-posterior (I-P) side. Conversely, an increase of rectum volume induces a compression from the I-P to the S-A side of the pelvic region. These compressive actions can be added or subtracted from each other, depending on their amplitudes and directions. Prostate motion occurs when a movement of the rectum is observed (this movement depends, itself, on lungs and bladder volume). The maximum movement of prostate is 9 mm considering maximal bladder or rectal action, and 11 mm considering maximum lung action. In some other cases, opposition of compressive effects can lead to stasis of the prostate. Based on the volumes of bladder, rectum, and lungs, it is possible to qualitatively estimate the movement of organs of the pelvic area. The best way to reduce prostate movement is to recommend the patient to have an empty rectum, with either full bladder and/or full lungs
Alain Noel - One of the best experts on this subject based on the ideXlab platform.
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Qualitative estimation of pelvic organ interactions and their consequences on prostate motion: Study on a Deceased Person
Medical Physics, 2006Co-Authors: Laurent Keros, Valérie Bernier, Pierre Aletti, Vincent Marchesi, Didier Wolf, Alain NoelAbstract:In an attempt to have better targeting of the prostate during radiotherapy it is necessary to understand the mechanical interactions between bladder, rectum, and prostate and estimate their consequences on prostate motion. For this, the volumes of bladder, rectum, and lungs were modified concomitantly on a Deceased Person. A CT acquisition was performed for each of these different pelvic configurations (36 acquisitions). An increase in the volume of the bladder or lungs induces a compression of tissues of the pelvic area from its supero-anterior (S-A) to infero-posterior (I-P) side. Conversely, an increase of rectum volume induces a compression from the I-P to the S-A side of the pelvic region. These compressive actions can be added or subtracted from each other, depending on their amplitudes and directions. Prostate motion occurs when a movement of the rectum is observed (this movement depends, itself, on lungs and bladder volume). The maximum movement of prostate is 9 mm considering maximal bladder or rectal action, and 11 mm considering maximum lung action. In some other cases, opposition of compressive effects can lead to stasis of the prostate. Based on the volumes of bladder, rectum, and lungs, it is possible to qualitatively estimate the movement of organs of the pelvic area. The best way to reduce prostate movement is to recommend the patient to have an empty rectum, with either full bladder and/or full lungs
Mohamed Haboussi - One of the best experts on this subject based on the ideXlab platform.
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Predictive model of the prostate motion in the context of radiotherapy: A biomechanical approach relying on urodynamic data and mechanical testing
Journal of the mechanical behavior of biomedical materials, 2015Co-Authors: Mohamed Boubaker, Mohamed Haboussi, Jean-françois Ganghoffer, Pierre AlettiAbstract:In this paper, a biomechanical approach relying on urodynamic data and mechanical tests is proposed for an accurate prediction of the motion of the pelvic organs in the context of the prostate radiotherapy. As a first step, an experimental protocol is elaborated to characterize the mechanical properties of the bladder and rectum wall tissues; uniaxial tensile tests are performed on porcine substrates. In a second step, the parameters of Ogden-type hyperelastic constitutive models are identified; their relevance in the context of the implementation of a human biomechanical model is verified by means of preliminary Finite Elements (FE) simulations against human urodynamic data. In a third step, the identified constitutive equations are employed for the simulations of the motion and interactions of the pelvic organs due to concomitant changes of the distension volumes of the urinary bladder and rectum. The effectiveness of the developed biomechanical model is demonstrated in investigating the motion of the bladder, rectum and prostate organs; the results in terms of displacements are shown to be in good agreement with measurements inherent to a Deceased Person, with a relative error close to 6%.
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finite element simulation of interactions between pelvic organs predictive model of the prostate motion in the context of radiotherapy
Journal of Biomechanics, 2009Co-Authors: Mohamed Bader Boubaker, Jean-françois Ganghoffer, Mohamed Haboussi, Pierre AlettiAbstract:The setting up of predictive models of the pelvic organ motion and deformation may prove an efficient tool in the framework of prostate cancer radiotherapy, in order to deliver doses more accurately and efficiently to the clinical target volume (CTV). A finite element (FE) model of the prostate, rectum and bladder motion has been developed, investigating more specifically the influence of the rectum and bladder repletions on the gland motion. The required organ geometries are obtained after processing the computed tomography (CT) images, using specific softwares. Due to their structural characteristics, a 3D shell discretization is adopted for the rectum and the bladder, whereas a volume discretization is adopted for the prostate. As for the mechanical behavior modelling, first order Ogden hyperelastic constitutive laws for both the rectum and bladder are identified. The prostate is comparatively considered as more rigid and is accordingly modelled as an elastic tissue undergoing small strains. A FE model is then created, accounting for boundary and contact conditions, internal and applied loadings being selected as close as possible to available anatomic data. The order of magnitude of the prostate motion predicted by the FE simulations is similar to the measurements done on a Deceased Person, accounting for the delineation errors, with a relative error around 8%. Differences are essentially due to uncertainties in the constitutive parameters, pointing towards the need for the setting up of direct measurement of the organs mechanical behavior.
Jean-françois Ganghoffer - One of the best experts on this subject based on the ideXlab platform.
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Predictive model of the prostate motion in the context of radiotherapy: A biomechanical approach relying on urodynamic data and mechanical testing
Journal of the mechanical behavior of biomedical materials, 2015Co-Authors: Mohamed Boubaker, Mohamed Haboussi, Jean-françois Ganghoffer, Pierre AlettiAbstract:In this paper, a biomechanical approach relying on urodynamic data and mechanical tests is proposed for an accurate prediction of the motion of the pelvic organs in the context of the prostate radiotherapy. As a first step, an experimental protocol is elaborated to characterize the mechanical properties of the bladder and rectum wall tissues; uniaxial tensile tests are performed on porcine substrates. In a second step, the parameters of Ogden-type hyperelastic constitutive models are identified; their relevance in the context of the implementation of a human biomechanical model is verified by means of preliminary Finite Elements (FE) simulations against human urodynamic data. In a third step, the identified constitutive equations are employed for the simulations of the motion and interactions of the pelvic organs due to concomitant changes of the distension volumes of the urinary bladder and rectum. The effectiveness of the developed biomechanical model is demonstrated in investigating the motion of the bladder, rectum and prostate organs; the results in terms of displacements are shown to be in good agreement with measurements inherent to a Deceased Person, with a relative error close to 6%.
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finite element simulation of interactions between pelvic organs predictive model of the prostate motion in the context of radiotherapy
Journal of Biomechanics, 2009Co-Authors: Mohamed Bader Boubaker, Jean-françois Ganghoffer, Mohamed Haboussi, Pierre AlettiAbstract:The setting up of predictive models of the pelvic organ motion and deformation may prove an efficient tool in the framework of prostate cancer radiotherapy, in order to deliver doses more accurately and efficiently to the clinical target volume (CTV). A finite element (FE) model of the prostate, rectum and bladder motion has been developed, investigating more specifically the influence of the rectum and bladder repletions on the gland motion. The required organ geometries are obtained after processing the computed tomography (CT) images, using specific softwares. Due to their structural characteristics, a 3D shell discretization is adopted for the rectum and the bladder, whereas a volume discretization is adopted for the prostate. As for the mechanical behavior modelling, first order Ogden hyperelastic constitutive laws for both the rectum and bladder are identified. The prostate is comparatively considered as more rigid and is accordingly modelled as an elastic tissue undergoing small strains. A FE model is then created, accounting for boundary and contact conditions, internal and applied loadings being selected as close as possible to available anatomic data. The order of magnitude of the prostate motion predicted by the FE simulations is similar to the measurements done on a Deceased Person, accounting for the delineation errors, with a relative error around 8%. Differences are essentially due to uncertainties in the constitutive parameters, pointing towards the need for the setting up of direct measurement of the organs mechanical behavior.
Bregje D Onwuteakaphilipsen - One of the best experts on this subject based on the ideXlab platform.
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proxy reporting in after death interviews the use of proxy respondents in retrospective assessment of chronic diseases and symptom burden in the terminal phase of life
Palliative Medicine, 2003Co-Authors: Marianne Klinkenberg, J H Smit, Dorly J H Deeg, Dick L Willems, Bregje D OnwuteakaphilipsenAbstract:This study evaluates the quality of data obtained from after-death interviews with significant others of Deceased older Persons regarding the prevalence of chronic diseases and symptoms in the terminal phase of life. These data are compared with reports from physicians and earlier self-reports from the Deceased Person. There were significant increases in nonresponse and nonavailability of significant others for decedents who had been divorced or had never been married, thus introducing some selection bias. At the level of the total sample, significant others seem to give accurate information about the prevalence of chronic diseases when compared with self-reports and reports from physicians. At the level of the individual sample member, after-death interviews with significant others provide valid information for the assessment of the prevalence of malignant neoplasms, diabetes mellitus, chronic obstructive pulmonary disease and cerebrovascular disease, but not for osteo- and rheumatoid arthritis and artherosclerotic disease. At the level of the total sample, the prevalence of symptoms assessed by significant others did not differ greatly from the assessment made by physicians. However, at the level of the individual sample member, the validity of symptom assessment by significant others could not be supported by data obtained from the physicians. With regard to the type of significant others interviewed, children reported more symptoms than partners. The use of significant others in after-death interviews can be a valid method with regard to the assessment of chronic diseases and symptoms on a group level. On an individual level this can be concluded only for chronic diseases with clearly observable consequences.
