Fundamental and Harmonic Ultrasound Image Joint Restoration

L'imagerie ultrasonore conserve sa place parmi les principales modalités d'imagerie en raison de ses capacités à révéler l'anatomie et à inspecter le mouvement des organes et le flux sanguin en temps réel, d'un manière non invasive et non ionisante, avec un faible coût, une facilité d'utilisation et une grande vitesse de reconstruction des images. Néanmoins, l'imagerie ultrasonore présente des limites intrinsèques en termes de résolution spatiale. L'amélioration de la résolution spatiale des images ultrasonores est un défi actuel et de nombreux travaux ont longtemps porté sur l'optimisation du dispositif d'acquisition. L'imagerie ultrasonore à haute résolution atteint cet objectif grâce à l'utilisation de sondes spécialisées, mais se confronte aujourd'hui à des limites physiques et technologiques. L'imagerie harmonique est la solution intuitive des spécialistes pour augmenter la résolution lors de l'acquisition. Cependant, elle souffre d'une atténuation en profondeur. Une solution alternative pour améliorer la résolution est de développer des techniques de post-traitement comme la restauration d'images ultrasonores. L'objectif de cette thèse est d'étudier la non-linéarité des échos ultrasonores dans le processus de restauration et de présenter l'intérêt d'incorporer des images US harmoniques dans ce processus. Par conséquent, nous présentons une nouvelle méthode de restauration d'images US qui utilise les composantes fondamentales et harmoniques de l'image observée. La plupart des méthodes existantes sont basées sur un modèle linéaire de formation d'image. Sous l'approximation de Born du premier ordre, l'image RF est supposée être une convolution 2D entre la fonction de réflectivité et la réponse impulsionelle du système. Par conséquent, un problème inverse résultant est formé et résolu en utilisant un algorithme de type ADMM. Plus précisément, nous proposons de récupérer la fonction de reflectivité inconnue en minimisant une fonction composée de deux termes de fidélité des données correspondant aux composantes linéaires (fondamentale) et non linéaires (première harmonique) de l'image observée, et d'un terme de régularisation basé sur la parcimonie afin de stabiliser la solution. Pour tenir compte de l'atténuation en profondeur des images harmoniques, un terme d'atténuation dans le modèle direct de l'image harmonique est proposé sur la base d'une analyse spectrale effectuée sur les signaux RF observés. La méthode proposée a d'abord été appliquée en deux étapes, en estimant d'abord la réponse impulsionelle, suivi par la fonction de réflectivité. Dans un deuxième temps, une solution pour estimer simultanément le réponse impulsionelle et la fonction de réflectivité est proposée, et une autre solution pour prendre en compte la variabilité spatiale du la réponse impulsionelle est présentée. L'intérêt de la méthode proposée est démontré par des résultats synthétiques et in vivo et comparé aux méthodes de restauration conventionnelles

Physical Activity and Obesity Indicators: National Cross Sectional Study on Lebanese Adults

Association between higher levels of physical activity and lower rates of obesity has been shown. The aim is to assess the relation between the prevalence of physical activity and the Physical Activity Index (PAI) of 300 Lebanese healthy adults, with age, gender, occupation, body mass indices and waist circumferences (WC). The cutoff points of WC for both genders were determined using the values of Body Mass Index (BMI). A cross-sectional study using self-reported valid questionnaire was conducted randomly on 150 men and 150 women, between 18 and 74 years, from Beirut region. Association between variables was performed using chi2, T-Test and ANOVA. Linear regression determined the WC cutoffs based on BMI. 22% of the population was obese with WC mean level of 92.47±14.4cm (87.71±14.4 cm for women and 97.24±12.96 cm for men). The prevalence of physical activity was 34% in overall population (27% in women and 40% in men).There was no significant association between BMI values and PAI (p< 0.085 for men and p< 0.300 for women). However there was an inverse association between WC values and PAI in both genders (p<0.043 in men and p< 0.036 in women). Linear regression showed WC cut-off point in Lebanese women with BMI ≥25 kg/m2 and ≥30 kg/m2 of 86 cm and 100 cm respectively, whereas for men it was 92.12 cm and 105 cm respectively. The prevalence of physical activity in Beirut is low with differences among genders. The highest physical activity index is associated with the decreased values of waist circumference

Restoration of ultrasonic images using non-linear system identification and deconvolution

This paper studies a new ultrasound image restoration method based on a non-linear forward model. A Hammerstein polynomial-based non-linear image formation model is considered to identify the system impulse response in baseband and around the second harmonic. The identification process is followed by a joint deconvolution technique minimizing an appropriate cost function. This cost function is constructed from two data fidelity terms exploiting the linear and non-linear model components, penalized by an additive-norm regularization enforcing sparsity of the solution. An alternating optimization approach is considered to minimize the penalized cost function, allowing the tissue reflectivity function to be estimated. Results on synthetic ultrasound images are finally presented to evaluate the algorithm performance

Worldwide trends in underweight and obesity from 1990 to 2022: a pooled analysis of 3663 population-representative studies with 222 million children, adolescents, and adults

Background Underweight and obesity are associated with adverse health outcomes throughout the life course. We estimated the individual and combined prevalence of underweight or thinness and obesity, and their changes, from 1990 to 2022 for adults and school-aged children and adolescents in 200 countries and territories. Methods We used data from 3663 population-based studies with 222 million participants that measured height and weight in representative samples of the general population. We used a Bayesian hierarchical model to estimate trends in the prevalence of different BMI categories, separately for adults (age ≥20 years) and school-aged children and adolescents (age 5–19 years), from 1990 to 2022 for 200 countries and territories. For adults, we report the individual and combined prevalence of underweight (BMI <18·5 kg/m2) and obesity (BMI ≥30 kg/m2). For schoolaged children and adolescents, we report thinness (BMI <2 SD below the median of the WHO growth reference) and obesity (BMI >2 SD above the median). Findings From 1990 to 2022, the combined prevalence of underweight and obesity in adults decreased in 11 countries (6%) for women and 17 (9%) for men with a posterior probability of at least 0·80 that the observed changes were true decreases. The combined prevalence increased in 162 countries (81%) for women and 140 countries (70%) for men with a posterior probability of at least 0·80. In 2022, the combined prevalence of underweight and obesity was highest in island nations in the Caribbean and Polynesia and Micronesia, and countries in the Middle East and north Africa. Obesity prevalence was higher than underweight with posterior probability of at least 0·80 in 177 countries (89%) for women and 145 (73%) for men in 2022, whereas the converse was true in 16 countries (8%) for women, and 39 (20%) for men. From 1990 to 2022, the combined prevalence of thinness and obesity decreased among girls in five countries (3%) and among boys in 15 countries (8%) with a posterior probability of at least 0·80, and increased among girls in 140 countries (70%) and boys in 137 countries (69%) with a posterior probability of at least 0·80. The countries with highest combined prevalence of thinness and obesity in school-aged children and adolescents in 2022 were in Polynesia and Micronesia and the Caribbean for both sexes, and Chile and Qatar for boys. Combined prevalence was also high in some countries in south Asia, such as India and Pakistan, where thinness remained prevalent despite having declined. In 2022, obesity in school-aged children and adolescents was more prevalent than thinness with a posterior probability of at least 0·80 among girls in 133 countries (67%) and boys in 125 countries (63%), whereas the converse was true in 35 countries (18%) and 42 countries (21%), respectively. In almost all countries for both adults and school-aged children and adolescents, the increases in double burden were driven by increases in obesity, and decreases in double burden by declining underweight or thinness. Interpretation The combined burden of underweight and obesity has increased in most countries, driven by an increase in obesity, while underweight and thinness remain prevalent in south Asia and parts of Africa. A healthy nutrition transition that enhances access to nutritious foods is needed to address the remaining burden of underweight while curbing and reversing the increase in obesit

Diminishing benefits of urban living for children and adolescents’ growth and development

Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified.This study was funded by: - The UK Medical Research Council (grant number MR/V034057/1) - The Wellcome Trust (Pathways to Equitable Healthy Cities grant 209376/Z/17/Z). - The AstraZeneca Young Health Programme and the European Commission (STOP project through EU Horizon 2020 research and innovation programme under Grant Agreement 774548)

Worldwide trends in underweight and obesity from 1990 to 2022 : a pooled analysis of 3663 population-representative studies with 222 million children, adolescents, and adults

A list of authors and their affiliations appears online. A supplementary appendix is herewith attached.Background: Underweight and obesity are associated with adverse health outcomes throughout the life course. We estimated the individual and combined prevalence of underweight or thinness and obesity, and their changes, from 1990 to 2022 for adults and school-aged children and adolescents in 200 countries and territories. Methods: We used data from 3663 population-based studies with 222 million participants that measured height and weight in representative samples of the general population. We used a Bayesian hierarchical model to estimate trends in the prevalence of different BMI categories, separately for adults (age ≥20 years) and school-aged children and adolescents (age 5–19 years), from 1990 to 2022 for 200 countries and territories. For adults, we report the individual and combined prevalence of underweight (BMI 2 SD above the median). Findings: From 1990 to 2022, the combined prevalence of underweight and obesity in adults decreased in 11 countries (6%) for women and 17 (9%) for men with a posterior probability of at least 0·80 that the observed changes were true decreases. The combined prevalence increased in 162 countries (81%) for women and 140 countries (70%) for men with a posterior probability of at least 0·80. In 2022, the combined prevalence of underweight and obesity was highest in island nations in the Caribbean and Polynesia and Micronesia, and countries in the Middle East and north Africa. Obesity prevalence was higher than underweight with posterior probability of at least 0·80 in 177 countries (89%) for women and 145 (73%) for men in 2022, whereas the converse was true in 16 countries (8%) for women, and 39 (20%) for men. From 1990 to 2022, the combined prevalence of thinness and obesity decreased among girls in five countries (3%) and among boys in 15 countries (8%) with a posterior probability of at least 0·80, and increased among girls in 140 countries (70%) and boys in 137 countries (69%) with a posterior probability of at least 0·80. The countries with highest combined prevalence of thinness and obesity in school-aged children and adolescents in 2022 were in Polynesia and Micronesia and the Caribbean for both sexes, and Chile and Qatar for boys. Combined prevalence was also high in some countries in south Asia, such as India and Pakistan, where thinness remained prevalent despite having declined. In 2022, obesity in school-aged children and adolescents was more prevalent than thinness with a posterior probability of at least 0·80 among girls in 133 countries (67%) and boys in 125 countries (63%), whereas the converse was true in 35 countries (18%) and 42 countries (21%), respectively. In almost all countries for both adults and school-aged children and adolescents, the increases in double burden were driven by increases in obesity, and decreases in double burden by declining underweight or thinness. Interpretation: The combined burden of underweight and obesity has increased in most countries, driven by an increase in obesity, while underweight and thinness remain prevalent in south Asia and parts of Africa. A healthy nutrition transition that enhances access to nutritious foods is needed to address the remaining burden of underweight while curbing and reversing the increase in obesity.peer-reviewe

Restauration conjointe des images ultrasonores fondamentales et harmoniques

L'imagerie ultrasonore conserve sa place parmi les principales modalités d'imagerie en raison de ses capacités à révéler l'anatomie et à inspecter le mouvement des organes et le flux sanguin en temps réel, d'un manière non invasive et non ionisante, avec un faible coût, une facilité d'utilisation et une grande vitesse de reconstruction des images. Néanmoins, l'imagerie ultrasonore présente des limites intrinsèques en termes de résolution spatiale. L'amélioration de la résolution spatiale des images ultrasonores est un défi actuel et de nombreux travaux ont longtemps porté sur l'optimisation du dispositif d'acquisition. L'imagerie ultrasonore à haute résolution atteint cet objectif grâce à l'utilisation de sondes spécialisées, mais se confronte aujourd'hui à des limites physiques et technologiques. L'imagerie harmonique est la solution intuitive des spécialistes pour augmenter la résolution lors de l'acquisition. Cependant, elle souffre d'une atténuation en profondeur. Une solution alternative pour améliorer la résolution est de développer des techniques de post-traitement comme la restauration d'images ultrasonores. L'objectif de cette thèse est d'étudier la non-linéarité des échos ultrasonores dans le processus de restauration et de présenter l'intérêt d'incorporer des images US harmoniques dans ce processus. Par conséquent, nous présentons une nouvelle méthode de restauration d'images US qui utilise les composantes fondamentales et harmoniques de l'image observée. La plupart des méthodes existantes sont basées sur un modèle linéaire de formation d'image. Sous l'approximation de Born du premier ordre, l'image RF est supposée être une convolution 2D entre la fonction de réflectivité et la réponse impulsionelle du système. Par conséquent, un problème inverse résultant est formé et résolu en utilisant un algorithme de type ADMM. Plus précisément, nous proposons de récupérer la fonction de reflectivité inconnue en minimisant une fonction composée de deux termes de fidélité des données correspondant aux composantes linéaires (fondamentale) et non linéaires (première harmonique) de l'image observée, et d'un terme de régularisation basé sur la parcimonie afin de stabiliser la solution. Pour tenir compte de l'atténuation en profondeur des images harmoniques, un terme d'atténuation dans le modèle direct de l'image harmonique est proposé sur la base d'une analyse spectrale effectuée sur les signaux RF observés. La méthode proposée a d'abord été appliquée en deux étapes, en estimant d'abord la réponse impulsionelle, suivi par la fonction de réflectivité. Dans un deuxième temps, une solution pour estimer simultanément le réponse impulsionelle et la fonction de réflectivité est proposée, et une autre solution pour prendre en compte la variabilité spatiale du la réponse impulsionelle est présentée. L'intérêt de la méthode proposée est démontré par des résultats synthétiques et in vivo et comparé aux méthodes de restauration conventionnelles.Ultrasound imaging maintains its position among the leading imaging modalities because of its abilities to reveal anatomy and inspect organ movement and blood flow in real time, with noninvasive, non-ionizing risk, low cost, ease of use, and high speed of image reconstruction. Nevertheless, ultrasound imaging has some intrinsic limitations in terms of its spatial resolution. Improving the spatial resolution of ultrasound images is a current challenge and many works have long been concerned with the optimization of the acquisition device. High-resolution ultrasound imaging achieves this goal through the use of specialized probes, but is now encountering physical and technological limitations.Harmonic imaging is the intuitive solution for specialists to increase the resolution during acquisition. However, it suffers from attenuation at depth. An alternative solution to improve resolution is to develop post-processing techniques as restoration of ultrasound images. The objective of this PhD thesis is to investigate the non-linearity of ultrasound echoes in the restoration process and present the interest of incorporating harmonic US images into the process. Therefore, we present a new US image restoration method that utilizes the fundamental and harmonic components of the observed image. Most of the existing methods are based on a linear image formation model. Under the first-order Born approximation, the RF image is assumed to be a 2D convolution between the TRF and the point spread function of the system. Therefore, a resulting inverse problem is formed and solved using an ADMM-like algorithm. More specifically, we propose to recover the unknown TRF by minimizing a function composed of two data fidelity terms corresponding to the linear (fundamental) and nonlinear (first harmonic) components of the observed image, and a sparsity-based regularization term to stabilize the solution. To account for the attenuation in the depth of harmonic images, an attenuation term in the direct model of the harmonic image is proposed based on a spectral analysis performed on the observed RF signals. The proposed method was first applied in a two- step manner: first estimating PSF, followed by estimating TRF. In a second step, a solution to simultaneously estimate the PSF and the TRF is proposed, and another solution to account for the spatial variability of the PSF is presented. The interest of the proposed method is shown on synthetic and in vivo results and compared with the conventional restoration methods

Restauration conjointe des images ultrasonores fondamentales et harmoniques

Ultrasound imaging maintains its position among the leading imaging modalities because of its abilities to reveal anatomy and inspect organ movement and blood flow in real time, with noninvasive, non-ionizing risk, low cost, ease of use, and high speed of image reconstruction. Nevertheless, ultrasound imaging has some intrinsic limitations in terms of its spatial resolution. Improving the spatial resolution of ultrasound images is a current challenge and many works have long been concerned with the optimization of the acquisition device. High-resolution ultrasound imaging achieves this goal through the use of specialized probes, but is now encountering physical and technological limitations.Harmonic imaging is the intuitive solution for specialists to increase the resolution during acquisition. However, it suffers from attenuation at depth. An alternative solution to improve resolution is to develop post-processing techniques as restoration of ultrasound images. The objective of this PhD thesis is to investigate the non-linearity of ultrasound echoes in the restoration process and present the interest of incorporating harmonic US images into the process. Therefore, we present a new US image restoration method that utilizes the fundamental and harmonic components of the observed image. Most of the existing methods are based on a linear image formation model. Under the first-order Born approximation, the RF image is assumed to be a 2D convolution between the TRF and the point spread function of the system. Therefore, a resulting inverse problem is formed and solved using an ADMM-like algorithm. More specifically, we propose to recover the unknown TRF by minimizing a function composed of two data fidelity terms corresponding to the linear (fundamental) and nonlinear (first harmonic) components of the observed image, and a sparsity-based regularization term to stabilize the solution. To account for the attenuation in the depth of harmonic images, an attenuation term in the direct model of the harmonic image is proposed based on a spectral analysis performed on the observed RF signals. The proposed method was first applied in a two- step manner: first estimating PSF, followed by estimating TRF. In a second step, a solution to simultaneously estimate the PSF and the TRF is proposed, and another solution to account for the spatial variability of the PSF is presented. The interest of the proposed method is shown on synthetic and in vivo results and compared with the conventional restoration methods.L'imagerie ultrasonore conserve sa place parmi les principales modalités d'imagerie en raison de ses capacités à révéler l'anatomie et à inspecter le mouvement des organes et le flux sanguin en temps réel, d'un manière non invasive et non ionisante, avec un faible coût, une facilité d'utilisation et une grande vitesse de reconstruction des images. Néanmoins, l'imagerie ultrasonore présente des limites intrinsèques en termes de résolution spatiale. L'amélioration de la résolution spatiale des images ultrasonores est un défi actuel et de nombreux travaux ont longtemps porté sur l'optimisation du dispositif d'acquisition. L'imagerie ultrasonore à haute résolution atteint cet objectif grâce à l'utilisation de sondes spécialisées, mais se confronte aujourd'hui à des limites physiques et technologiques. L'imagerie harmonique est la solution intuitive des spécialistes pour augmenter la résolution lors de l'acquisition. Cependant, elle souffre d'une atténuation en profondeur. Une solution alternative pour améliorer la résolution est de développer des techniques de post-traitement comme la restauration d'images ultrasonores. L'objectif de cette thèse est d'étudier la non-linéarité des échos ultrasonores dans le processus de restauration et de présenter l'intérêt d'incorporer des images US harmoniques dans ce processus. Par conséquent, nous présentons une nouvelle méthode de restauration d'images US qui utilise les composantes fondamentales et harmoniques de l'image observée. La plupart des méthodes existantes sont basées sur un modèle linéaire de formation d'image. Sous l'approximation de Born du premier ordre, l'image RF est supposée être une convolution 2D entre la fonction de réflectivité et la réponse impulsionelle du système. Par conséquent, un problème inverse résultant est formé et résolu en utilisant un algorithme de type ADMM. Plus précisément, nous proposons de récupérer la fonction de reflectivité inconnue en minimisant une fonction composée de deux termes de fidélité des données correspondant aux composantes linéaires (fondamentale) et non linéaires (première harmonique) de l'image observée, et d'un terme de régularisation basé sur la parcimonie afin de stabiliser la solution. Pour tenir compte de l'atténuation en profondeur des images harmoniques, un terme d'atténuation dans le modèle direct de l'image harmonique est proposé sur la base d'une analyse spectrale effectuée sur les signaux RF observés. La méthode proposée a d'abord été appliquée en deux étapes, en estimant d'abord la réponse impulsionelle, suivi par la fonction de réflectivité. Dans un deuxième temps, une solution pour estimer simultanément le réponse impulsionelle et la fonction de réflectivité est proposée, et une autre solution pour prendre en compte la variabilité spatiale du la réponse impulsionelle est présentée. L'intérêt de la méthode proposée est démontré par des résultats synthétiques et in vivo et comparé aux méthodes de restauration conventionnelles

Restauration conjointe des images ultrasonores fondamentales et harmoniques

Ultrasound imaging maintains its position among the leading imaging modalities because of its abilities to reveal anatomy and inspect organ movement and blood flow in real time, with noninvasive, non-ionizing risk, low cost, ease of use, and high speed of image reconstruction. Nevertheless, ultrasound imaging has some intrinsic limitations in terms of its spatial resolution. Improving the spatial resolution of ultrasound images is a current challenge and many works have long been concerned with the optimization of the acquisition device. High-resolution ultrasound imaging achieves this goal through the use of specialized probes, but is now encountering physical and technological limitations.Harmonic imaging is the intuitive solution for specialists to increase the resolution during acquisition. However, it suffers from attenuation at depth. An alternative solution to improve resolution is to develop post-processing techniques as restoration of ultrasound images. The objective of this PhD thesis is to investigate the non-linearity of ultrasound echoes in the restoration process and present the interest of incorporating harmonic US images into the process. Therefore, we present a new US image restoration method that utilizes the fundamental and harmonic components of the observed image. Most of the existing methods are based on a linear image formation model. Under the first-order Born approximation, the RF image is assumed to be a 2D convolution between the TRF and the point spread function of the system. Therefore, a resulting inverse problem is formed and solved using an ADMM-like algorithm. More specifically, we propose to recover the unknown TRF by minimizing a function composed of two data fidelity terms corresponding to the linear (fundamental) and nonlinear (first harmonic) components of the observed image, and a sparsity-based regularization term to stabilize the solution. To account for the attenuation in the depth of harmonic images, an attenuation term in the direct model of the harmonic image is proposed based on a spectral analysis performed on the observed RF signals. The proposed method was first applied in a two- step manner: first estimating PSF, followed by estimating TRF. In a second step, a solution to simultaneously estimate the PSF and the TRF is proposed, and another solution to account for the spatial variability of the PSF is presented. The interest of the proposed method is shown on synthetic and in vivo results and compared with the conventional restoration methods.L'imagerie ultrasonore conserve sa place parmi les principales modalités d'imagerie en raison de ses capacités à révéler l'anatomie et à inspecter le mouvement des organes et le flux sanguin en temps réel, d'un manière non invasive et non ionisante, avec un faible coût, une facilité d'utilisation et une grande vitesse de reconstruction des images. Néanmoins, l'imagerie ultrasonore présente des limites intrinsèques en termes de résolution spatiale. L'amélioration de la résolution spatiale des images ultrasonores est un défi actuel et de nombreux travaux ont longtemps porté sur l'optimisation du dispositif d'acquisition. L'imagerie ultrasonore à haute résolution atteint cet objectif grâce à l'utilisation de sondes spécialisées, mais se confronte aujourd'hui à des limites physiques et technologiques. L'imagerie harmonique est la solution intuitive des spécialistes pour augmenter la résolution lors de l'acquisition. Cependant, elle souffre d'une atténuation en profondeur. Une solution alternative pour améliorer la résolution est de développer des techniques de post-traitement comme la restauration d'images ultrasonores. L'objectif de cette thèse est d'étudier la non-linéarité des échos ultrasonores dans le processus de restauration et de présenter l'intérêt d'incorporer des images US harmoniques dans ce processus. Par conséquent, nous présentons une nouvelle méthode de restauration d'images US qui utilise les composantes fondamentales et harmoniques de l'image observée. La plupart des méthodes existantes sont basées sur un modèle linéaire de formation d'image. Sous l'approximation de Born du premier ordre, l'image RF est supposée être une convolution 2D entre la fonction de réflectivité et la réponse impulsionelle du système. Par conséquent, un problème inverse résultant est formé et résolu en utilisant un algorithme de type ADMM. Plus précisément, nous proposons de récupérer la fonction de reflectivité inconnue en minimisant une fonction composée de deux termes de fidélité des données correspondant aux composantes linéaires (fondamentale) et non linéaires (première harmonique) de l'image observée, et d'un terme de régularisation basé sur la parcimonie afin de stabiliser la solution. Pour tenir compte de l'atténuation en profondeur des images harmoniques, un terme d'atténuation dans le modèle direct de l'image harmonique est proposé sur la base d'une analyse spectrale effectuée sur les signaux RF observés. La méthode proposée a d'abord été appliquée en deux étapes, en estimant d'abord la réponse impulsionelle, suivi par la fonction de réflectivité. Dans un deuxième temps, une solution pour estimer simultanément le réponse impulsionelle et la fonction de réflectivité est proposée, et une autre solution pour prendre en compte la variabilité spatiale du la réponse impulsionelle est présentée. L'intérêt de la méthode proposée est démontré par des résultats synthétiques et in vivo et comparé aux méthodes de restauration conventionnelles

Deconvolution for improved multifractal characterization of tissues in ultrasound images

International audienceSeveral existing studies showed the interest of estimating the multifractal properties of tissues in ultrasound (US) imaging. However, US images are not carrying information only about the tissues, but also about the US scanner. Deconvolution methods are a common way to restore the tissue reflectivity function, but, to our knowledge, their impact on estimated fractal or multifractal behavior has not been studied yet. The objective of this paper is to investigate this influence through a dedicated simulation pipeline and an in vivo experiment