Modélisation biomécanique du diaphragme humain : du CT-4D au modèle du mouvement

Session "Articles"National audienceL'hadronthérapie est une technique avancée de traitement du cancer par radiothérapie. Elle offre une balistique d'irradiation bien supérieure à la radiothérapie conventionnelle. Lorsque la tumeur se trouve sur un organe en mouvement, la difficulté majeure est de pouvoir la cibler pendant le traitement. En ce qui concerne la tumeur pulmonaire, le diaphragme joue un rôle majeur et prépondérant dans le mouvement tumoral. Le diaphragme est une membrane musculo-tendineuse en forme de dôme qui sépare le thorax de l'abdomen. Dans ce travail nous présentons un modèle biomécanique permettant de modéliser les mouvements du diaphragme pendant la respiration. Dans cette démarche nous simulons le mouvement du diaphragme entre l'inspiration et l'expiration, à partir d'un modèle de contraction musculaire. Pour cela, un modèle biomécanique 3D personnalisé du diaphragme, basé sur la méthode des éléments finis, a été développé à partir de données expérimentales (4D CT-scan) d'un patient. Les résultats de notre modélisation montrent une bonne concordance entre la simulation et les données expérimentales

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake

Appropriate Biomechanics and kinematics Modeling of the respiratory System: Human Diaphragm and Thorax

International audienceTumor motion during irradiation reduces target coverage and increases dose to healthy tissues. Prediction of respiratory motion has the potential to substantially improve cancer radiation therapy. The respiratory motion is complex and its prediction is not a simple task, especially that breathing is controlled by the independent action of the diaphragm muscles and thorax. The diaphragm is the principal muscle used in the process of respiration and its modeling is essential for assessing the respiratory motion. In this context, an accurate patient-specific finite element(FE) based biomechanical model can be used to predict diaphragm deformation. In this paper, we have developed a FE model of the respiratory system including the diaphragm behavior and the complete thorax with musculoskeletal structure. These incorporate the ribs kinematics extracted directly from the Computed Tomography (CT) scan images. In order to demonstrate the effectiveness of our biomechanical model, a qualitative and quantitative comparison between the FE simulations and the CT scan images were performed. Upon application of linear elastic models, our results show that a linear elastic model can accurately predict diaphragm deformations. These comparisons demonstrate the effectiveness of the proposed physically-based model. The developed computational model could be a valuable tool for respiratory system deformation prediction in order to be controlled and monitored by external sensors during the treatment

Sports injuries in students aged 12-18 during physical education classes in Israel

A retrospective study was made of sports injuries occurring in physical education classes in 51 junior and senior high schools in Israel during a period of 14 months (2000-2002). The survey covered a total population of 11439 students aged 12 to 18, 52% male, 48% female. The aim of the study was to assess the incidence, types and risk factors involving sports injuries among students in physical education classes. Physical education teachers were asked to complete questionnaires recording injuries that occurred during their lessons. Data included: socio-demographic parameters (gender, age, height and weight of the injured students), area and type of injury, time of injury during the class, type of sport activity, previous injuries, assessment of sport capabilities and performance. A total of 192 injuries were recorded in the survey (1.70%). Male and female students had fairly similar injury rates (49% female, 51% male). 12-14 year old students showed the greatest number of injuries (52%). The ankle was the most common site of injury in both genders (48%) mostly involving ankle sprain. Athletics was the most common sport involving injury (38%). 45% of injuries were reported to occur in the start of the class, whereas 26% of injuries were repeat injuries. This survey showed that the incidence of injuries during supervised physical education classes in high schools in Israel is relatively low and is similar to that of other Western countries

Biomechanical-based respiratory motion-compensation for 4D dose calculation during hadron therapy

International audienceHadron therapy is an advanced radiotherapy technique for cancer treatment. It offers a better irradiation ballistic than conventional techniques and requires an appropriate quality assurance procedures. Tumor motion during irradiation reduces target coverage and increases dose to healthy tissues. Unfortunately, the continuous organ density changes due to respiratory motion and affect the ranges of ions which can lead to unwanted dose distributions in the case of lung tumors. Accurate 4D dosimetry calculations are important for treatment planning verification and evaluation. They require temporal information about the tumor position, size and shape, as well as information regarding the tissue density variation along the beam path during treatment. For more precision, several studies have focused on the biomechanical models of the respiratory system based on finite element method. These approaches are based on continuum mechanics of materials properties, mesh organ geometry, as well as anatomical boundary conditions. However, so far, they do not take completely into account density variations needed for dose calculations. In this context, Velec et al. have developed a model that incorporates rigid body motion and deformation (RBD) in order to study the impact of respiratory-induced organ motion on dose calculation for liver tumors. They use linear interpolation to modulate the dose distribution previously calculated from exhale position to inhale position in each tetrahedral element for these intermediate breathing states

4D radiotherapeutic dose calculation using biomechanical respiratory motion description

International audienceOrgan motion due to patient breathing introduces a technical challenge for dosimetry and lung tumor treatment by hadrontherapy. Accurate dose distribution estimation requires patient-specic information on tumor position, size, and shape as well as information regarding the material density and stopping power of the media along the beam path. A new 4D dosimetry method was developed, which can be coupled to any motion estimation method. As an illustration, the new method was implemented and tested with a biomechanical model and clinical data

Human Liver Multiphysics Modeling for 4D Dosimetry During Hadrontherapy

International audienceOrgan motion, especially respiratory motion, is a technical challenge to hadrontherapy planning and dosimetry. This motion induces the displacement and the deformation of the organs tissues along the radiation beam path which need to be taken into account when computating dose distribution during the treatment. In this paper we present an original approach of virtual patient modeling for 4D radiation therapy simulations. As opposed to classical image-based models, where the necessary information is distributed over a rigid structured grid of voxels, we represent the human anatomy with a deformable grid of tetrahedra where the mass density is mapped to the vertices of the grid. In this way, we can simulate within the same structure organ motion, mass density variations and dose distribution without having to perform voxel tissue tracking