A biomechanical approach for real-time tracking of lung tumors during External Beam Radiation Therapy (EBRT)

Lung cancer is the most common cause of cancer related death in both men and women. Radiation therapy is widely used for lung cancer treatment. However, this method can be challenging due to respiratory motion. Motion modeling is a popular method for respiratory motion compensation, while biomechanics-based motion models are believed to be more robust and accurate as they are based on the physics of motion. In this study, we aim to develop a biomechanics-based lung tumor tracking algorithm which can be used during External Beam Radiation Therapy (EBRT). An accelerated lung biomechanical model can be used during EBRT only if its boundary conditions (BCs) are defined in a way that they can be updated in real-time. As such, we have developed a lung finite element (FE) model in conjunction with a Neural Networks (NNs) based method for predicting the BCs of the lung model from chest surface motion data. To develop the lung FE model for tumor motion prediction, thoracic 4D CT images of lung cancer patients were processed to capture the lung and diaphragm geometry, trans-pulmonary pressure, and diaphragm motion. Next, the chest surface motion was obtained through tracking the motion of the ribcage in 4D CT images. This was performed to simulate surface motion data that can be acquired using optical tracking systems. Finally, two feedforward NNs were developed, one for estimating the trans-pulmonary pressure and another for estimating the diaphragm motion from chest surface motion data. The algorithm development consists of four steps of: 1) Automatic segmentation of the lungs and diaphragm, 2) diaphragm motion modelling using Principal Component Analysis (PCA), 3) Developing the lung FE model, and 4) Using two NNs to estimate the trans-pulmonary pressure values and diaphragm motion from chest surface motion data. The results indicate that the Dice similarity coefficient between actual and simulated tumor volumes ranges from 0.76±0.04 to 0.91±0.01, which is favorable. As such, real-time lung tumor tracking during EBRT using the proposed algorithm is feasible. Hence, further clinical studies involving lung cancer patients to assess the algorithm performance are justified

Development and Validation Methodology of the Nuss Procedure Surgical Planner

Pectus excavatum (PE) is a congenital chest wall deformity which is characterized, in most cases, by a deep depression of the sternum. A minimally invasive technique for the repair of PE (MIRPE), often referred to as the Nuss procedure, has been proven to be more advantageous than many other PE treatment techniques. The Nuss procedure consists of placement of a metal bar(s) underneath the sternum, thereby forcibly changing the geometry of the ribcage. Because of the prevalence of PE and the popularity of the Nuss procedure, the demand to perform this surgery is greater than ever. Therefore, a Nuss procedure surgical planner would be an invaluable planning tool ensuring an optimal physiological and aesthetic outcome. In this dissertation, the development and validation of the Nuss procedure planner is investigated. First, a generic model of the ribcage is developed to overcome the issue of missing cartilage when PE ribcages are segmented and facilitate the flexibility of the model to accommodate a range of deformity. Then, the CT data collected from actual patients with PE is used to create a set of patient specific finite element models. Based on finite element analyses performed over those models, a set force-displacement data set is created. This data is used to train an artificial neural network to generalize the data set. In order to evaluate the planning process, a methodology which uses an average shape of the chest for comparison with results of the Nuss procedure planner is developed. This method is based on a sample of normal chests obtained from the ODU male population using laser surface scanning and overcomes challenging issues such as hole-filling, scan registration and consistency. Additionally, this planning simulator is optimized so that it can be used for training purposes. Haptic feedback and inertial tracking is implemented, and the force-displacement model is approximated using a neural network approach and evaluated for real-time performance. The results show that it is possible to utilize this approximation of the force-displacement model for the Nuss procedure simulator. The detailed ribcage model achieves real-time performance

Occupant protection design with FE human body models

The second leading cause of occupant fatalities in traffic accidents are thoracic injuries. Sternal fractures are the most typical moderate thoracic injury in frontal crash. Until now there is no clear understanding about the sternal injury mechanisms and how to minimize the risk of sternal fracture of the occupants. The design and assessment of advanced restraint systems capable to minimize such injuries is currently based on the Hybrid-III 50th percentile (H350) dummy in frontal crash. Despite the great benefits achieved with the H350 dummy, the inclusion of transducers and specific metrics for sternal loading were not part of its design purposes nor the representation of age-dependent factors. This suggests a gap of information in the design process of a restraint system. This gap could lead to an erroneous optimization of the system in terms of sternal injury risk minimization. It was hypothesized that the restraint design process needs to be complemented with more accurate and biofidelic tools, as human body models (HBMs), in terms of sternal loading minimization. A comparative analysis was needed. Three dimensions have been addressed in order to analyze the hypothesis: (i) Development of a novel elderly human model called Thums-elderly (based on the Thums-original) in order to address age-dependency factors and realistic geometrical properties of the thoracic cortical bone. This development included novel µCT data from PMHS and a multi-level validation process. (ii) Development of thoracic injury risk assessment methods for HBMs aiming for a direct comparison against dummy predictions. (iii) Comparison of the driver and passenger injury prediction of the dummy model and both HBMs (Thums-original and Thums-elderly) in a wide range of crash severities including a real-world accident reconstruction. A total of 168 occupant simulations were run and analyzed. The comparison addressed four different restraint systems including three adaptive restraint system variants. The assessment methods were grouped on rib fracture risk and sternal fracture risk. Sternal fracture risk was approached using HBM simulations by comparing two loadcases (non-injurious and injurious in terms of sternal fractures). Bending moments at the second inter-costal space (ICS_2) suggested to be a realistic criterion to quantify the risk of sternal fractures. An injury reference value of resultant moments at the second ICS “MXYZ ICS_2” of 20 Nm was proposed. Out of the benchmark crash cases, it was found that the H350 may underestimate the risk of thoracic injuries and sternal fractures particularly in frontal crash cases with considerably high lateral pulses. This is inherent to the H350 design purposes (frontal-crash dedicated dummy), nevertheless the dummy is currently still an injury prediction tool in assessment programs with crash cases precisely addressing lateral pulses as oblique barriers, offset deformable barriers, small-overlaps and accident reconstructions. For sternal fracture risk, the H350 is a not applicable tool, as this dummy was not designed to accurately measure sternal loading nor predict a risk of sternal fracture. An example of this fact was shown with the restraint system variant A (accident reconstruction case): A rather low AIS3 injury risk with the H350 indicated a safe design (at least for severe injuries) while no metrics of sternal loading or fracture risk were generated. The same variant tested with the HBMs showed an increased risk of sternal fracture. Restraint system variants (B, C and D) showed loading reduction with the HBMs up to non-injurious levels (under 20Nm). The same variants showed rather a marginal benefit with the H350. Lateral pulses are also believed to have an influence on the injury outcome of the front passengers, as the restraint system force transfer will be different due to the asymmetry of the belt paths. This effect is shown with the HBMs in terms of AIS2 (as sternal fracture). Regarding the effects of introducing age dependent factors (represented by the Thums-elderly), a reduced thorax stiffness was found in local- (component-) and body-region validation loadcases, specifically for cartilage, sternum and upper ribs. As the analysis was restricted to morphological dependency rather than material or failure limits, a “fragility” of the elderly model was not clearly represented. Nevertheless, the structural deformation is believed to be realistic due to the improvement achieved by introducing real cortical thicknesses from µCT data, especially on the sternal region. The Thums-elderly showed to be less sensitive, in terms of sternal loading, to successive shoulder belt force reduction than the Thums-original in high severity pulses. Sternal fractures and other moderate injuries will play an important role in the near future as optimization target in restraint system design. Sternal loading and sternal fracture risk need to be accurately predicted in order to assess the mitigation capabilities of a specific restraint system. While current dummies seem to be insufficient to reach the needed accuracy, HBMs show potential to assume this task. A simulation matrix with different crash severities and restraint system variants was built for benchmark purposes. The benchmark showed that current H350 dummies are not capable to discriminate noticeable improvements at sternal loading level, whereas HBMs do. Ageing and its effect on sternal fracture risk cannot be neither correctly represent with dummies. In order to represent ageing effects, HBMs need to be improved (e.g. realistic cortical thickness distribution and cartilage calcification). The injury prediction of an improved “elderly” HBM (Thums-elderly) showed to be strong dependent on the crash severity, although, it showed a less sensitive response to restraint loading reduction compared to the HBM without age-dependent factors (Thums-original).Nach Kopfverletzungen sind Thoraxverletzungen die zweithäufigste Todesursache bei Verkehrsunfällen. Darunter sind Brustbeinfrakturen die häufigsten mittelschweren Thorax-verletzungen in Frontalaufprall-Unfällen. Gegenwärtig gibt es weder eine eindeutige Erklärung bzgl. des Verletzungsmechanismus von Brustbeinfrakturen noch klare Strategien, um deren Risiko in der Insassenschutzauslegung zu minimieren. Die aktuelle Auslegung im Frontalaufprall basiert auf Messwerten des Hybrid-III 50th Prozent (H350) Dummys. Dessen Verletzungs-prognose anhand der gemessenen Werte lassen eine eingeschränkte Bewertung der Effektivität des Rückhaltesystems erstellen. Der Dummy und dessen Messtechnik mangelt an Sensoren spezifisch für die Bewertung von Brustbein-verletzungen. Darüber hinaus wurde eine altersabhängige Prognose nicht dazu mitentwickelt. Diese Fakten weisen auf eine inkomplette Analyse in der Insassenschutzauslegung für die Minimierung der Brustbeinverletzungen hin. Die Hypothese lautet deshalb, dass diese „Lücke“ des Hardware- und virtuellen Entwicklungsprozesses durch genauere und biofidelere Modelle (es entspricht Menschmodellen) gelöst werden kann. Eine vergleichende Analyse von Dummy vs. Menschmodell ist dazu erforderlich. Die Analyse der Hypothese erfolgte anhand drei Schritten: (i) Entwicklung eines neuen Menschmodells „Thums-elderly“ (basiert auf Thums-original), um altersabhängige Faktoren und realistischerer Kortikalis (Kortikalschicht) der Rippen nachzubilden. Diese Entwicklung enthält neuartige µCT Daten von PMHS und die Ergebnisse eines Mehrebenen-Validierungsprozesses. (ii) Entwicklung der Auswertungsmethoden spezifisch für Menschmodelle gezielt um die Vergleichbarkeit zur Dummy-Prognose zu gewährleisten. (iii) Vergleichende Analyse Dummy vs. Menschmodell auf Fahrer- und Beifahrerpositionen in einem breiteren Spektrum von Unfallschweren. Ein Realunfall wurde ebenfalls rekonstruiert und analysiert. Insgesamt wurden 168 Insassensimulationen durchgeführt und ausgewertet. Der Vergleich adressiert ebenso vier Rückhaltesystemvarianten, drei davon adaptiv. Die Auswertungsmethode der Simulationen mit Menschmodellen wurde in Rippenfrakturen und Brustbeinfrakturen unterteilt. Biegeversuche und Gurtstraffung wurden mit dem Menschmodell nachsimuliert, um Verletzungskriterien für Brustbeinfrakturen zu definieren und zu quantifizieren. Binäre Versuchsergebnisse (Verletzung oder Nicht-Verletzung) dienten als Referenz. Die Biegemomente auf ICS_2 (zweiter interkostalraum) zeigten sich als realistisches Kriterium). Als Verletzungsreferenzwert (IRV) ist ein resultierendes Biegemoment auf ICS_2 (MXYZ ICS_2) von 20 Nm vorgeschlagen. Anhand der simulierten Lastfälle wurde festgestellt, dass der H350 zu einer Unterprognose des Risikos der Thoraxverletzungen tendiert, insbesondere in Frontallastfällen mit erheblichen Lateralpulsen. Diese Unterprognose erklärt sich teilweise dadurch, dass der Dummy spezifisch für Frontalcrashanwendung ausgelegt wurde. Jedoch wird der Dummy aktuell noch als Auswertungstool in Gesetz- und Verbraucherschutzlastfälle eingesetzt, obwohl die oben genannten Lateralpulse präsent sind (z.B. Oblique- und Offset-deformable Barrieren, Small-overlaps und Unfallrekonstruktionen). Für eine Prognose der Brustbeinverletzungen ist der H350 weder dazu ausgelegt noch wurden Verletzungsrisikokurven spezifisch dafür entwickelt. Ein Beispiel dafür ist die Verletzungsprognose in der Unfallrekonstruktion (siehe Rückhaltesystem Variante A, Kapitel 4.3): Bei der Betrachtung der Ergebnisse liefert die Prognose des Dummys ein niedriges AIS3+ Verletzungsrisiko. Diese Prognose entspricht prinzipiell einer robusten Performance des Rückhaltesystems. Dabei ist zu beachten, dass keine Informationen bzgl. der Brustbein-belastungen bzw. dem Verletzungsrisiko generiert sind. Auf der anderen Seite weist die Simulation mit dem Menschmodell (ebenso Rückhaltesystem Variante A) ein höheres Verletzungsrisiko des Brustbeins auf. Darüber hinaus zeigten die Rückhaltesystemvarianten B, C und D eine stetige Reduktion der Belastung bis zu einem optimalen Punkt unter dem Verletzungsreferenzwert (20 Nm). Die gleichen Varianten mit dem H350 zeigen eine minimale Verbesserung, allerdings immer auf ein AIS3+ Niveau bezogen. Die Prognosegüte des Menschmodells weist zusätzlich darauf hin, dass die Verletzungs-wahrscheinlichkeit auch in Abhängigkeit der Insassenposition (Fahrer oder Beifahrer) zu betrachten ist, insbesondere bei Lastfällen mit Lateralpulsen, bei welchen die asymmetrische Konstellation der Schulter-gurtverlauf einem anderen Deformationsmuster des Brustkorbes entsprechen muss. Dieser Effekt ist nur mit dem Menschmodell quantifizierbar, wenn auf dem Beifahrerbrustbein gemessene Biegemomente vom Fahrerbrustbein abweichen. Bzgl. altersabhängigen Effekten weist die Anwendung von einem altersabhängigen Menschmodell (Thums-Elderly) eine reduzierte Steifigkeit auf. Dies geht aus der Validierung der Körperregion des Brustkorbs und einzelnen Komponenten insbesondere Knorpel, Brustbein und obere Rippen hervor. Die vergleichende Analyse mit dem Thums-elderly war beschränkt auf eine morphologische Abhängigkeit. Altersabhängige Materialparameter wie Fließkurven und Versagenskriterien blieben unverändert. Eine typische „Zerbrechlichkeit“ wurde mit dem modifizierten Modell nicht komplett abgebildet. Nichtsdestotrotz erreicht das Thums-elderly ein realistisches Deformationsmuster anhand der Anwendung von µCT Daten für die Kortikalis (Kortikalschicht) der Rippen und des Brustbeins. Das Thums-elderly weist zusätzlich eine geringere Sensitivität bei sukzessiver Senkung des Niveaus des Gurtkraftbegrenzers im Vergleich mit Thums-original auf. Allerdings ist dieser Effekt nur bei Lastfällen mit „härteren“ Pulsen zu erkennen. Brustbeinfrakturen und andere mittelschwere Verletzungen werden eine wichtige Rolle als Optimierungsziel bei der Auslegung zukünftiger Rückhaltesysteme spielen. Dazu ist eine realistische Prognose dieser Verletzungen notwendig, um eine korrekte Auslegung und Optimierung des Rückhaltesystems durchzuführen. Aktuelle Dummys sind nicht in der Lage, eine realistische Prognose dieser Verletzungen zu generieren. HBMs zeigen ein deutliches Potential, um diese Aufgabe zu übernehmen. Eine Simulationsmatrix mit einem breiten Spektrum von Crashschweren und Rückhaltsystemen wurde als Benchmarkbasis aufgebaut. Die Ergebnisse aus dem H350 zeigen bei einer stetigen Reduktion der Rückhaltbelastung keine Reduktion des Brustbeinverletzungsrisikos. Mit HBMs zeigt diese Reduktion jedoch eine deutliche Minimierung dieses Risikos. Eine Altersabhängigkeit des Brustbeinverletzungsrisikos ist nicht von aktuellen Dummys prognostizierbar. Nur optimierte HBMs werden altersabhängige Effekte korrekt nachbilden. Faktoren wie eine realistischere Kortikalschicht und ein korrektes Verknöcherungsmuster der Knorpel sind erforderlich. Die Verletzungsprognose eines optimierten „altersabhängigen“ HBM (Thums-elderly) zeigt eine starke Abhängigkeit von der Crashschwere, es zeigt jedoch eine geringere Sensitivität nach einer Reduktion der Rückhaltbelastung im Vergleich zu dem nicht-altersabhängigen HBM (Thums-original)

SIMBIO-M 2014, SIMulation technologies in the fields of BIO-Sciences and Multiphysics: BioMechanics, BioMaterials and BioMedicine, Marseille, France, june 2014

Proceedings de la 3ème édition de la conférence internationale Simbio-M (2014). Organisée conjointement par l'IFSTTAR, Aix-Marseille Université, l'université de Coventry et CADLM, cette conférence se concentre sur les progrès des technologies de simulation dans les domaines des sciences du vivant et multiphysiques: Biomécanique, Biomatériaux et Biomédical. L'objectif de cette conférence est de partager et d'explorer les résultats dans les techniques d'analyse numérique et les outils de modélisation mathématique. Cette approche numérique permet des études prévisionnelles ou exploratoires dans les différents domaines des biosciences

Detailed subject-specific FE rib modeling for fracture prediction

Objective: The current state of the art human body models (HBMs) underpredict the number of\ua0fractured ribs. Also, it has not been shown that the models can predict the fracture locations. Efforts have been made to create subject specific rib models for fracture prediction, with mixed results. The aim of this study is to evaluate if subject-specific finite element (FE) rib models, based\ua0on state-of-the-art clinical CT data combined with subject-specific material data, can predict rib\ua0stiffness and fracture location in anterior-posterior rib bending.Method: High resolution clinical CT data was used to generate detailed subject-specific geometry\ua0for twelve FE models of the sixth rib. The cortical bone periosteal and endosteal surfaces were\ua0estimated based on a previously calibrated cortical bone mapping algorithm. The cortical and the\ua0trabecular bone were modeled using a hexa-block algorithm. The isotropic material model for the\ua0cortical bone in each rib model was assigned subject-specific material data based on tension coupon tests.\ua0\ua0Two different modeling strategies were used for the trabecular bone.\ua0The capability of the FE model to predict fracture location was carried out by modeling physical\ua0dynamic anterior-posterior rib bending tests. The rib model predictions were directly compared to the results from the tests. The predicted force-displacement time history, strain measurements at\ua0four locations, and rotation of the rib ends were compared to the results from the physical tests\ua0by means of CORA analysis. Rib fracture location in the FE model was estimated as the position\ua0for the element with the highest first principle strain at the time corresponding to rib fracture in\ua0the physical test.Results: Seven out of the twelve rib models predicted the fracture locations (at least for one of\ua0the trabecular modeling strategies) and had a force-displacement CORA score above 0.65. The\ua0other five rib models, had either a poor force-displacement CORA response or a poor fracture\ua0location prediction. It was observed that the stress-strain response for the coupon test for these\ua0five ribs showed significantly lower Young’s modulus, yield stress, and elongation at fracture compared to the other seven ribs.Conclusion: This study indicates that rib fracture location can be predicted for subject specific rib\ua0models based on high resolution CT, when loaded in anterior-posterior bending, as long as the\ua0rib’s cortical cortex is of sufficient thickness and has limited porosity. This study provides guide-lines for further enhancements of rib modeling for fracture location prediction with HBMs

Organ-focused mutual information for nonrigid multimodal registration of liver CT and Gd–EOB–DTPA-enhanced MRI

Accurate detection of liver lesions is of great importance in hepatic surgery planning. Recent studies have shown that the detection rate of liver lesions is significantly higher in gadoxetic acid-enhanced magnetic resonance imaging (Gd–EOB–DTPA-enhanced MRI) than in contrast-enhanced portal-phase computed tomography (CT); however, the latter remains essential because of its high specificity, good performance in estimating liver volumes and better vessel visibility. To characterize liver lesions using both the above image modalities, we propose a multimodal nonrigid registration framework using organ-focused mutual information (OF-MI). This proposal tries to improve mutual information (MI) based registration by adding spatial information, benefiting from the availability of expert liver segmentation in clinical protocols. The incorporation of an additional information channel containing liver segmentation information was studied. A dataset of real clinical images and simulated images was used in the validation process. A Gd–EOB–DTPA-enhanced MRI simulation framework is presented. To evaluate results, warping index errors were calculated for the simulated data, and landmark-based and surface-based errors were calculated for the real data. An improvement of the registration accuracy for OF-MI as compared with MI was found for both simulated and real datasets. Statistical significance of the difference was tested and confirmed in the simulated dataset (p < 0.01)

Use of Parametric Finite Element Models to Investigate Effects of Occupant Characteristics on Lower-Extremity Injuries in Frontal Crashes.

The lower extremities are the body region at greatest risk of serious injury in frontal motor-vehicle crashes. Age, sex, and body mass index (BMI) affect the risks of clinically significant lower-extremity injuries such that women, older occupants, and occupants with higher BMI are at increased risk of these injuries in frontal crashes. Computational simulation is the most efficient way to characterize the biomechanical factors that explain the effects of age, sex, and BMI on lower-extremity injury risk. This type of simulation requires a finite element (FE) model with geometry that is parametric with these characteristics. This research developed and validated such a parametric FE whole-body model and used it to explore the effects of variations in lower-extremity geometry, material properties, body size, and body shape on lower-extremity injury risk. The parametric whole-body FE model was based on statistical models of lower-extremity bone surface geometry and cross-sectional geometry. These models were developed by morphing and fitting template FE meshes onto bone geometries extracted from CT data. Principal component analysis was applied to the resulting nodal coordinates and linear regression on principal component scores was used to develop models that describe how geometry varies with age, stature, and BMI. The parametric FE whole-body model was developed by combining the mesh geometries predicted by the statistical lower-extremity bone models, an existing external body surface shape model, and material properties that varied with age. Whole-body FE models associated with specific sets of characteristics were developed by positioning the lower-extremity bones inside the external surface model using surface model landmarks. A template whole-body mesh was then morphed to the external surface shape using the positioned lower-extremity bone models as fixed location landmarks. Simulations were performed with these models to investigate effects of occupant characteristics on lower-extremity injury risk. Frontal crash simulations with the whole-body models showed that age and BMI significantly affect strain values and peak forces, agreeing with the hypotheses that elderly and high BMI occupants are at increased risk of lower-extremity injury.PHDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113339/1/katklein_1.pd

Detrimental Thoracoabdominal Interaction With Lateral Airbag Restraints

Side impact motor vehicle crashes pose unique challenges for occupant protection, particularly with regard to torso injury mitigation. The minimal crush distance between the vehicle exterior and the occupant torso has necessitated advanced passive safety technologies in response to tightened regulatory requirements and increased public awareness of safety issues. In particular, lateral airbag restraints (side airbags) have undergone a rapid and unregulated introduction in recent years, with US availability increasing to over 90% of new vehicles in 2010. As with frontal airbag restraints, the prdissertationsity for injury to occupants in close proximity to side airbag deployment remains a concern. Test protocols have been proposed to evaluate occupant injury risk from airbag deployment with mechanical occupant surrogates. Yet few studies have attempted to characterize thoracoabdominal responses to close-proximity airbag contact in actual crashes, leaving unaddressed the relevance of test protocols and occupant surrogates currently employed. To address this issue, the present study sought to identify and characterize injury and biomechanical responses of the thoracoabdominal region to torso-interacting side airbag restraints. A novel biological experimental approach was developed from a multi-body analysis and from an evaluation of documented restraint performance. Biomechanical responses of deflection, deflection rate, the Viscous Criterion, and deformation obliquity with respect to subject anatomy were quantified. Further, tissue-level material response was examined through a comparative finite element analysis of subject-specific loading. Results indicated that traumatic visceral injury specific to the posterolateral region was associated with close-proximity airbag interaction. Deformation response was uniquely oblique with respect to anatomy, necessitating the refinement of existing injury metrics. Biomechanical tolerances were also determined for risk of trauma to posterolateral viscera. These results are useful for the development of mechanical occupant surrogates and reductions to injury risks from close-proximity side airbag loading

Validation of the SAFER Human Body Model Kinematics in Far-Side Impacts

Human Body Models are essential for real-world occupant protection assessment. With the overall purpose to create a robust human body model which is biofidelic in a variety of crash situations, this study aims to evaluate the biofidelity of the SAFER human body model in far-side impacts. The pelvis, torso and the upper and lower extremities of the SAFER human body model were updated. In addition, the shoulder area was updated for improved shoulder belt interaction in far-side impacts. The model was validated using kinematic corridors based on published human subject test data from two far-side impact set-ups, one simplified and one vehicle-based. The simplified far-side set-up included six configurations with different parameter settings, and the vehicle-based included two configurations: with and without far-side airbag, respectively. The updated SAFER HBM was robust and in general the model predicted the published human subject responses (kinematic CORA score &gt; 0.65) for all configurations in both test set-ups. An exception was a 90 degree far-side impact with the D-ring in the forward position, in the simplified set-up. Here the model could not predict the shoulder belt retention, resulting in a low CORA score. Based on the overall results, the model is considered valid to be used for assessment of far-side impact countermeasures

Automatic Image Segmentation of Healthy and Atelectatic Lungs in Computed Tomography

Computed tomography (CT) has become a standard in pulmonary imaging which allows the analysis of diseases like lung nodules, emphysema and embolism. The improved spatial and temporal resolution involves a dramatic increase in the amount of data that has to be stored and processed. This has motivated the development of computer aided diagnostics (CAD) systems that have released the physician from the tedious task of manually delineating the boundary of the structures of interest from such a large number of images, a pre-processing step known as image segmentation. Apart from being impractical, the manual segmentation is prone to high intra and inter observer subjectiveness. Automatic segmentation of the lungs with atelectasis poses a challenge because in CT images they have similar texture and gray level as the surrounding tissue. Consequently, the available graphical information is not sufficient to distinguish the boundary of the lung. The present work aims to close the existing gap left by the segmentation of atelectatic lungs in volume CT data. A-priori knowledge of anatomical information plays a key role in the achievement of this goal