Toward a real time multi-tissue Adaptive Physics-Based Non-Rigid Registration framework for brain tumor resection

This paper presents an adaptive non-rigid registration method for aligning pre-operative MRI with intra-operative MRI (iMRI) to compensate for brain deformation during brain tumor resection. This method extends a successful existing Physics-Based Non-Rigid Registration (PBNRR) technique implemented in ITKv4.5. The new method relies on a parallel adaptive heterogeneous biomechanical Finite Element (FE) model for tissue/tumor removal depicted in the iMRI. In contrast the existing PBNRR in ITK relies on homogeneous static FE model designed for brain shift only (i.e., it is not designed to handle brain tumor resection). As a result, the new method (1) accurately captures the intra-operative deformations associated with the tissue removal due to tumor resection and (2) reduces the end-to-end execution time to within the time constraints imposed by the neurosurgical procedure. The evaluation of the new method is based on 14 clinical cases with: (i) brain shift only (seven cases), (ii) partial tumor resection (two cases), and (iii) complete tumor resection (five cases). The new adaptive method can reduce the alignment error up to seven and five times compared to a rigid and ITK\u27s PBNRR registration methods, respectively. On average, the alignment error of the new method is reduced by 9.23 and 5.63 mm compared to the alignment error from the rigid and PBNRR method implemented in ITK. Moreover, the total execution time for all the case studies is about 1 min or less in a Linux Dell workstation with 12 Intel Xeon 3.47 GHz CPU cores and 96 GB of RAM

On the Real-Time Performance, Robustness and Accuracy of Medical Image Non-Rigid Registration

Three critical issues about medical image non-rigid registration are performance, robustness and accuracy. A registration method, which is capable of responding timely with an accurate alignment, robust against the variation of the image intensity and the missing data, is desirable for its clinical use. This work addresses all three of these issues. Unacceptable execution time of Non-rigid registration (NRR) often presents a major obstacle to its routine clinical use. We present a hybrid data partitioning method to parallelize a NRR method on a cooperative architecture, which enables us to get closer to the goal: accelerating using architecture rather than designing a parallel algorithm from scratch. to further accelerate the performance for the GPU part, a GPU optimization tool is provided to automatically optimize GPU execution configuration.;Missing data and variation of the intensity are two severe challenges for the robustness of the registration method. A novel point-based NRR method is presented to resolve mapping function (deformation field) with the point correspondence missing. The novelty of this method lies in incorporating a finite element biomechanical model into an Expectation and Maximization (EM) framework to resolve the correspondence and mapping function simultaneously. This method is extended to deal with the deformation induced by tumor resection, which imposes another challenge, i.e. incomplete intra-operative MRI. The registration is formulated as a three variable (Correspondence, Deformation Field, and Resection Region) functional minimization problem and resolved by a Nested Expectation and Maximization framework. The experimental results show the effectiveness of this method in correcting the deformation in the vicinity of the tumor. to deal with the variation of the intensity, two different methods are developed depending on the specific application. For the mono-modality registration on delayed enhanced cardiac MRI and cine MRI, a hybrid registration method is designed by unifying both intensity- and feature point-based metrics into one cost function. The experiment on the moving propagation of suspicious myocardial infarction shows effectiveness of this hybrid method. For the multi-modality registration on MRI and CT, a Mutual Information (MI)-based NRR is developed by modeling the underlying deformation as a Free-Form Deformation (FFD). MI is sensitive to the variation of the intensity due to equidistant bins. We overcome this disadvantage by designing a Top-to-Down K-means clustering method to naturally group similar intensities into one bin. The experiment shows this method can increase the accuracy of the MI-based registration.;In image registration, a finite element biomechanical model is usually employed to simulate the underlying movement of the soft tissue. We develop a multi-tissue mesh generation method to build a heterogeneous biomechanical model to realistically simulate the underlying movement of the brain. We focus on the following four critical mesh properties: tissue-dependent resolution, fidelity to tissue boundaries, smoothness of mesh surfaces, and element quality. Each mesh property can be controlled on a tissue level. The experiments on comparing the homogeneous model with the heterogeneous model demonstrate the effectiveness of the heterogeneous model in improving the registration accuracy

Explore the Dynamic Characteristics of Dental Structures: Modelling, Remodelling, Implantology and Optimisation

The properties of a structure can be both narrowly and broadly described. The mechanical properties, as a narrow sense of property, are those that are quantitative and can be directly measured through experiments. They can be used as a metric to compare the benefits of one material versus another. Examples include Young’s modulus, tensile strength, natural frequency, viscosity, etc. Those with a broader definition, can be hardly measured directly. This thesis aims to study the dynamic properties of dental complex through experiments, clinical trials and computational simulations, thereby bridging some gaps between the numerical study and clinical application. The natural frequency and mode shapes, of human maxilla model with different levels of integrities and properties of the periodontal ligament (PDL), are obtained through the complex modal analysis. It is shown that the comprehensiveness of a computational model significantly affects the characterisation of dynamic behaviours, with decreasing natural frequencies and changed mode shapes as a result of the models with higher extents of integrity and preciseness. It is also found that the PDL plays a very important role in quantifying natural frequencies. Meanwhile, damping properties and the heterogeneity of materials also have an influence on the dynamic properties of dental structures. The understanding of dynamic properties enables to further investigate how it can influence the response when applying an external stimulus. In a parallel preliminary clinical trial, 13 patients requiring bilateral maxillary premolar extractions were recruited and applied with mechanical vibrations of approximately 20 g and 50 Hz, using a split mouth design. It is found that both the space closure and canine distalisation of the vibration group are significantly faster and higher than those of the control group (p<0.05). The pressure within the PDL is computationally calculated to be higher with the vibration group for maxillary teeth for both linguo-buccal and mesial-distal directions. A further increased PDL response can be observed if increasing the frequency until reaching a local natural frequency. The vibration of 50 Hz or higher is thus approved to be a potential stimulus accelerating orthodontic treatment. The pivotal role of soft tissue the PDL is further studied by quantitatively establishing pressure thresholds regulating orthodontic tooth movement (OTM). The centre of resistance and moment to force ratio are also examined via simulation. Distally-directed tipping and translational forces, ranging from 7.5 g to 300 g, are exerted onto maxillary teeth. The hydrostatic stress is quantified from nonlinear finite element analysis (FEA) and compared with normal capillary and systolic blood pressure for driving the tissue remodelling. Localised and volume-averaged hydrostatic stress are introduced to describe OTM. By comparing with clinical results in past literature, the volume average of hydrostatic stress in PDL was proved to describe the process of OTM more indicatively. Global measurement of hydrostatic pressure in the PDL better characterised OTM, implying that OTM occurs only when the majority of PDL volume is critically stressed. The FEA results provide new insights into relevant orthodontic biomechanics and help establish optimal orthodontic force for a specific patient. Implant-supported fixed partial denture (FPD) with cantilever extension can transfer excessive load to the bone surrounding implants and stress/strain concentration which potentially leads to bone resorption. The immediate biomechanical response and long-term bone remodelling outcomes are examined. It is indicated that during the chewing cycles, the regions near implant necks and apexes experience high von Mises stress (VMS) and equivalent strain (EQS) than the middle regions in all configurations, with or without the cantilever. The patient-specific dynamic loading data and CT based mandibular model allow us to model the biomechanical responses more realistically. The results provide the data for clinical assessment of implant configuration to improve longevity and reliability of the implant-supported FPD restoration. On the other hand, the results show that the three-implant supported and distally cantilevered FPDs see noticeable and continuous bone apposition, mainly adjacent to the cervical and apical regions. The bridged and mesially cantilevered FPDs show bone resorption or no visible bone formation in some areas. Caution should be taken when selecting the FPD with cantilever due to the risk of overloading bone resorption. The position of FPD pontics plays a critical role in mechanobiological functionality and bone remodelling. As an important loading condition of dental biomechanics, the accurate assignment of masticatory loads has long been demanded. Methods involving different principles have been applied to acquire or assess the muscular co-activation during normal or unhealthy stomatognathic functioning. Their accuracy and capability of direct quantification, especially when using alone, are however questioned. We establish a clinically validated Sequential Kriging Optimisation (SKO) model, coupled with the FEM and in vivo occlusal records, to further the understanding of muscular functionality following a fibula free flap (FFF) surgery. The results, within the limitations of the current study, indicates the statistical advantage of agreeing occlusal measurements and hence the reliability of using the SKO model over the traditionally adopted optimality criteria. It is therefore speculated that mastication is not optimally controlled to a definite degree. It is also found that the maximum muscular capacity slightly decreases whereas the actual muscle forces fluctuate over the 28-month period

Medical-Data-Models.org:A collection of freely available forms (September 2016)

MDM-Portal (Medical Data-Models) is a meta-data repository for creating, analysing, sharing and reusing medical forms, developed by the Institute of Medical Informatics, University of Muenster in Germany. Electronic forms for documentation of patient data are an integral part within the workflow of physicians. A huge amount of data is collected either through routine documentation forms (EHRs) for electronic health records or as case report forms (CRFs) for clinical trials. This raises major scientific challenges for health care, since different health information systems are not necessarily compatible with each other and thus information exchange of structured data is hampered. Software vendors provide a variety of individual documentation forms according to their standard contracts, which function as isolated applications. Furthermore, free availability of those forms is rarely the case. Currently less than 5 % of medical forms are freely accessible. Based on this lack of transparency harmonization of data models in health care is extremely cumbersome, thus work and know-how of completed clinical trials and routine documentation in hospitals are hard to be re-used. The MDM-Portal serves as an infrastructure for academic (non-commercial) medical research to contribute a solution to this problem. It already contains more than 4,000 system-independent forms (CDISC ODM Format, www.cdisc.org, Operational Data Model) with more than 380,000 dataelements. This enables researchers to view, discuss, download and export forms in most common technical formats such as PDF, CSV, Excel, SQL, SPSS, R, etc. A growing user community will lead to a growing database of medical forms. In this matter, we would like to encourage all medical researchers to register and add forms and discuss existing forms

Disfunção vascular nos doentes com coarctação da aorta tratada

RESUMO: As cardiopatias congénitas (CC) afetam aproximadamente 1% dos recémnascidos e são responsáveis pela maior proporção de mortalidade infantil nos países desenvolvidos. A coarctação da aorta (CoA), a 6ª CC mais frequente, consiste numa estenose da aorta descendente proximal. Se não for tratada, tem uma história natural desfavorável. A cirurgia, dilatação com balão e a implantação de stent são atualmente técnicas que podem atingir o objetivo de uma remoção eficaz e duradoura da estenose ístmica, sendo a decisão baseada na idade doente, anatomia da CoA e preferência do operador ou da instituição. Contudo, um bom resultado anatómico não evita morbilidade e mortalidade de longo prazo, apresentando cerca de metade dos doentes hipertensão arterial (HTA), e registando-se mortalidade precoce, maioritariamente devido a complicações cardiovasculares e acidentes vasculares cerebrais. O perfil tensional anómalo sugere que os resultados subótimos possam ser secundários a disfunção vascular, cuja existência foi bem documentada em doentes com CoA tratada. Existem anomalias intrínsecas da estrutura arterial e função, alterações da sensibilidade neuro-hormonal ou da regulação endócrina, e fatores adquiridos, como a idade do tratamento, que contribuem para esta disfunção vascular. Os maus resultados a longo prazo podem resultar igualmente do tipo de tratamento efetuado, que provavelmente impactam de modo diverso a rigidez do istmo aórtico e potencialmente comprometem as funções da aorta. Este efeito da modalidade terapêutica não foi até ao momento estudado. A CoA não é uma simples doença mecânica que fica resolvida quando é removido o obstáculo. Objetivos e Hipóteses: O objetivo deste estudo é comparar a função vascular entre diferentes modalidades terapêuticas de CoA. A hipótese principal é a de que os doentes submetidos a dilatação com balão têm melhor função vascular que os doentes submetidos a cirurgia ou implantação de stent, pois aquela modalidade terapêutica tem menor potencial para danificar a integridade e propriedades biomecânicas da parede da aorta do que estas. Métodos: Avaliação prospetiva da função vascular usando múltiplas modalidades não invasivas, de modo a comparar os resultados de três grupos de doentes com CoA, tratados com dilatação com cirurgia, balão ou implantação de stent, após controle das variáveis de confusão. Em doentes com CoA tratada com sucesso, comparámos prospectivamente a rigidez da aorta com tonometria de aplanação e ressonância magnética cardíaca; função endotelial com tonometria arterial periférica endotelial; analise da onda de pulso com tonometria de aplanação e tonometria arterial periférica endotelial; massa ventricular esquerda e anatomia do arco aórtico com ressonância magnética cardíaca; marcadores séricos de função endotelial, inflamação, função da parede arterial e matriz extracelular; e saúde cardiovascular ideal. A análises estatística incluiu ajuste para as variáveis de confusão. Resultados: O estudo foi realizado em sete grandes centros, de Portugal e Estados Unidos da América. Foram incluídos 75 doentes, tratado por cirurgia (n=28), dilatação com balão (n=23) e implantação de stent (n=24). Os grupos tiveram idade semelhante à data de inclusão, gravidade da CoA, gradiente residual e perfil metabólico, mas eram diferentes quanto à idade à data do tratamento. A HTA, rigidez da aorta, função endotelial e massa ventricular eram semelhantes entre os grupos. Contudo, o grupo da dilatação com balão tinha mais distensibilidade regional da aorta ascendente, menor tensão arterial (TA) sistólica durante o exercício, menos alteração da variação noturna da TA, e dose menor de biomarcadores inflamatórios. Os resultados permaneceram inalterados após ajuste das potenciais variáveis de confusão, incluindo idade à data do tratamento. Conclusões: A modalidade terapêutica não estava associada à presença de HTA, rigidez arterial global e função endotelial. Contudo, os doentes com dilatação com balão tinham um perfil de função vascular mais favorável, caracterizado por maior distensibilidade da aorta ascendente, TA noturna mais baixa, menor resposta hipertensiva no esforço e menores marcadores séricos de inflamação. São necessários mais estudos para confirmar se os nossos resultados poderão contribuir para o refinamento do paradigma de tratamento da CoA, ao adicionar ao objetivo de remoção da estenose, a preservação da função vascular, quando dois ou mais tratamentos são aplicáveis.ABSTRACT: Introduction: Congenital heart disease (CHD) affects approximately 1% of liveborns and accounts for the largest proportion of infant mortality in developed countries. Coarctation of the aorta (CoA), the 6th most common CHD, consists of a narrowing of the proximal descending aorta. If left untreated, it has an unfavorable natural history. Surgery, balloon dilation (BD) or stent implantation are all current treatments that can achieve a successful long-term removal of the stenosis, and the choice is based on age, CoA anatomy, and personal or institutional preference. Coarctation is not a mere mechanical disease that is treated by removing the increased afterload. In fact, a good anatomic result does not avoid long-term cardiovascular (CV) morbidity and mortality, with late systemic hypertension (HTN) in approximately half of the patients, and reduced life expectancy, mostly due to CV complications and stroke. The abnormal blood pressure (BP) phenotype suggests that the suboptimal results are likely due to abnormal vascular function, which has been well documented in patients with repaired CoA. There are inherent changes in the arterial structure and function, impaired neuronal sensitivity or endocrinal auto-regulation, and acquired features, such as age at treatment, that contribute to vascular dysfunction in CoA. The poor long-term vascular outcome may also be impacted by the different types of repair, which likely have differing effects on the stiffness of the repaired segment and potentially compromise both the conduit and cushioning functions of the aorta. The effects of treatment modality on long-term vascular function remain uncharacterized. Aims and Hypothesis: The goal of this study is to assess vascular function in this patient population for comparison among the treatment modalities. The central hypothesis of this study was that patients who have undergone successful BD will have better vascular function than patients who have undergone successful surgical repair or stenting since this modality is least likely to damage the integrity and biomechanical properties of the aortic wall. Methods: Prospective assessment of vascular function using multiple non-invasive modalities, and compare the results among the three groups of CoA patients previously treated using surgery, BD or stent implantation after frequency matching for confounding variables. In successfully repaired CoA patients, we prospectively compared aortic stiffness by applanation tonometry and cardiac magnetic resonance (CMR); endothelial function by endothelial pulse amplitude testing; pulse waveform analysis by applanation tonometry and endothelial pulse amplitude testing; BP phenotype by office BP, ambulatory BP monitoring, and BP response to exercise; left ventricular (LV) mass and aortic morphometrics by CMR; blood biomarkers of endothelial function, inflammation, vascular wall function, and extracellular matrix; and ideal cardiovascular health. In the statistical analysis, we adjusted for potential confounders. Results: This study was done in seven, large volume centers from Portugal and the United States of America. Participants included 75 patients treated with surgery (n=28), BD (n=23), or stent (n=24). Groups had similar age at enrollment, CoA severity, residual gradient, and metabolic profile but differed by age at treatment. Systemic HTN, aortic stiffness, endothelial function, and LV mass were similar among groups. However, BD had more distensible ascending aortas, lower peak systolic BP during exercise, less impairment in diurnal BP variation, and lower inflammatory biomarkers. The results were unchanged after adjustment for potential confounders, including age at treatment. Conclusions: Treatment modality was not associated with major vascular outcomes such as systemic HTN, global aortic stiffness, and endothelial function. However, BD patients had a better vascular phenotype profile characterized by higher ascending aorta distensibility, lower night-time BP, lower peak exercise BP and lower levels of inflammatory markers. Further studies are required to confirm if our results may contribute to refining the CoA treatment paradigm by adding to the goals of therapy the preservation of vascular function when two or more treatment techniques are applicable

Pan European Voice Conference - PEVOC 11

The Pan European VOice Conference (PEVOC) was born in 1995 and therefore in 2015 it celebrates the 20th anniversary of its establishment: an important milestone that clearly expresses the strength and interest of the scientific community for the topics of this conference. The most significant themes of PEVOC are singing pedagogy and art, but also occupational voice disorders, neurology, rehabilitation, image and video analysis. PEVOC takes place in different European cities every two years (www.pevoc.org). The PEVOC 11 conference includes a symposium of the Collegium Medicorum Theatri (www.comet collegium.com