Århus, Denmark
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Andersen E.S.,Aarhus University Hospital | Noe K.O.,University of Aarhus | Noe K.O.,Alexandra Institute | Sorensen T.S.,University of Aarhus | And 6 more authors.
Radiotherapy and Oncology | Year: 2013

Background and purpose: Variations in organ position, shape, and volume cause uncertainties in dose assessment for brachytherapy (BT) in cervix cancer. The purpose of this study was to evaluate uncertainties associated with bladder dose accumulation based on DVH parameter addition (previously called "the worst case assumption") in fractionated BT. Materials and methods: Forty-seven patients treated for locally advanced cervical cancer were included. All patients received EBRT combined with two individually planned 3D image-guided adaptive BT fractions. D2cm 3 and D0.1 cm 3were estimated by DVH parameter addition and compared to dose accumulations based on an in-house developed biomechanical deformable image registration (DIR) algorithm. Results: DIR-based DVH analysis was possible in 42/47 patients. DVH parameter addition resulted in mean dose deviations relative to DIR of 0.4 ± 0.3 Gyαβ3 (1.5 ± 1.8%) and 1.9 ± 1.6 Gyαβ3 (5.2 ± 4.2%) for D2cm 3 and D0.1cm 3 respectively. Dose deviations greater than 5% occurred in 2% and 38% of the patients for D2 cm 3 and D0.1cm 3 respectively. Visual inspection of the dose distributions showed that hotspots were located in the same region of the bladder during both BT fractions for the majority of patients. Conclusion: DVH parameter addition provides a good estimate for D2cm 3 whereas D0.1cm 3 is less robust to this approximation. © 2013 Elsevier Ireland Ltd. All rights reserved.


Dalgaard L.G.,Alexandra Institute | Gronvall E.,University of Aarhus | Verdezoto N.,University of Aarhus
Proceedings of the 2013 7th International Conference on Pervasive Computing Technologies for Healthcare and Workshops, PervasiveHealth 2013 | Year: 2013

Several projects have shown that self-management of medication in private homes can be challenging. Many projects focused on specific illness-related approaches (e.g. diabetes) or practical issues such as how to handle medication while travelling. However, designing for everyday medication management involves more than just specific illness-related strategies and should take into account the broad set of activities conforming people's everyday life. This study investigates how older adults manage their medication in everyday life. To inform the design of pervasive healthcare medication management systems (PHMMS), the study calls for attention to medication-specific particularities that account for: according to need medication, the heterogeneous care network, the substitute medication, the medication informational order, the shared responsibility and the adjustment of medication intake. These medication particularities can enhance the individual's medication overview and support the understanding of medication intake in everyday life. The study also presents five design principles for future design of PHMMS. © 2013 ICST.


Verdezoto N.,University of Aarhus | Olsen J.W.,Alexandra Institute
IHI'12 - Proceedings of the 2nd ACM SIGHIT International Health Informatics Symposium | Year: 2012

Several technologies have been developed to support people's medication management, including pillboxes, specialized software applications, reminders and paper-based medication lists. Several of these technologies were discovered in older adults' homes during user studies carried out with the main purpose to help them to manage their medications and recall challenges. We confirm that a considerable number of older adults integrate their medication treatments into their daily life routines, and that the lack of knowledge, caregiver's support, medicine outside the home, forgetting medication intake, complexity of medication regimen were equally important challenges. One of the major findings was the issue related to substitutions, as older adults get confused due to the volatile information that they receive regarding their medications. We define basic requirements in order to address these issues towards the design of a personalized medication management system. We further describe our initial stage in a participatory design process as part of the ongoing Lev Vel Consortium. Copyright © 2012 ACM.


Christensen H.Bae.,University of Aarhus | Hansen K.M.,Copenhagen University | Kyng M.,University of Aarhus | Kyng M.,Alexandra Institute | Manikas K.,Copenhagen University
Information and Software Technology | Year: 2014

Context Telemedicine, the provision of health care at a distance, is arguably an effective way of increasing access to, reducing cost of, and improving quality of care. However, the deployment of telemedicine is faced with standards that are hard to use, application-specific data models, and application stove-pipes that inhibit the adoption of telemedical solutions. To which extent can a software ecosystem approach to telemedicine alleviate this? Objective In this article, we define the concept of software ecosystem architecture as the structure(s) of a software ecosystem comprising elements, relations among them, and properties of both. Our objective is to show how this concept can be used (i) in the analysis of existing software ecosystems and (ii) in the design of new software ecosystems. Method We performed a mixed-method study that consisted of a case study and an experiment. For (i), we performed a descriptive, revelatory case study of the Danish telemedicine ecosystem and for (ii), we experimentally designed, implemented, and evaluated the architecture of 4S. Results We contribute in three areas. First, we define the software ecosystem architecture concept that captures organization, business, and software aspects of software ecosystems. Secondly, we apply this concept in our case study and demonstrate that it is a viable concept for software ecosystem analysis. Finally, based on our experiments, we discuss the practice of software engineering for software ecosystems drawn from experience in creating and evolving the 4S telemedicine ecosystem. Conclusion The concept of software ecosystem architecture can be used analytically and constructively in respectively the analysis and design of software ecosystems. © 2014 Elsevier B.V.


Noe K.O.,University of Aarhus | Noe K.O.,Alexandra Institute | Sorensen T.S.,University of Aarhus
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

We present an algorithm for solid organ registration of pre-segmented data represented as tetrahedral meshes. Registration of the organ surface is driven by force terms based on a distance field representation of the source and reference shapes. Registration of internal morphology is achieved using a non-linear elastic finite element model. A key feature of the method is that the user does not need to specify boundary conditions (surface point correspondences) prior to the finite element analysis. Instead the boundary matches are found as an integrated part of the analysis. The method is evaluated on phantom data and prostate data obtained in vivo based on fiducial marker accuracy and inverse consistency of transformations. The parallel nature of the method allows an efficient implementation on a GPU and as a result the method is very fast. All validation registrations take less than 30 seconds to complete. The proposed method has many potential uses in image guided radiotherapy (IGRT) which relies on registration to account for organ deformation between treatment sessions. © 2010 Springer-Verlag.


Dalgaard L.G.,Alexandra Institute | Gronvall E.,University of Aarhus | Verdezoto N.,University of Aarhus
Proceedings - 2013 IEEE International Conference on Healthcare Informatics, ICHI 2013 | Year: 2013

Healthcare activities in private home settings that are not supervised by a healthcare professional can challenge older adults. To support such unsupervised care activities, an increasingly number of reminders and monitoring systems are designed. However, most of these systems target a specific treatment or a specific condition. In this paper, we discuss experiences from designing the tablet-based application MediFrame. MediFrame is a personal medication management system to support older adults in non-clinical settings such as the home. The paper describes the user-centered design process and the resulting tablet application. We show how MediFrame can be used to support adherence in medical treatments through fieldwork informed use scenarios. Based on early qualitative feedback, we also discuss lessons learned and how designers can support a holistic medication experience for an older adult's everyday life. © 2013 IEEE.


Jakobsen T.P.,Alexandra Institute | Makkes M.X.,TU Eindhoven | Nielsen J.D.,Alexandra Institute
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

We present an efficient implementation of the Orlandi protocol which is the first implementation of a protocol for multiparty computation on arithmetic circuits, which is secure against up to n-1 static, active adversaries. An efficient implementation of an actively secure self-trust protocol enables a number of multiparty computation where one or more of the parties only trust himself. Examples includes auctions, negotiations, and online gaming. The efficiency of the implementation is largely obtained through an efficient implementation of the Paillier cryptosystem, also described in this paper. © 2010 Springer-Verlag Berlin Heidelberg.


Andersen S.A.W.,Rigshospitalet | Mikkelsen P.T.,Alexandra Institute | Konge L.,Center for Clinical Education | Caye-Thomasen P.,Rigshospitalet | Sorensen M.So.,Rigshospitalet
Laryngoscope | Year: 2016

Objectives/Hypothesis Cognitive load theory states that working memory is limited. This has implications for learning and suggests that reducing cognitive load (CL) could promote learning and skills acquisition. This study aims to explore the effect of repeated practice and simulator-integrated tutoring on CL in virtual reality (VR) mastoidectomy simulation. Study Design Prospective trial. Methods Forty novice medical students performed 12 repeated virtual mastoidectomy procedures in the Visible Ear Simulator: 21 completed distributed practice with practice blocks spaced in time and 19 participants completed massed practice (all practices performed in 1 day). Participants were randomized for tutoring with the simulator-integrated tutor function. Cognitive load was estimated by measuring reaction time in a secondary task. Data were analyzed using linear mixed models for repeated measurements. Results The mean reaction time increased by 37% during the procedure compared with baseline, demonstrating that the procedure placed substantial cognitive demands. Repeated practice significantly lowered CL in the distributed practice group but not in massed practice group. In addition, CL was found to be further increased by 10.3% in the later and more complex stages of the procedure. The simulator-integrated tutor function did not have an impact on CL. Conclusion Distributed practice decreased CL in repeated VR mastoidectomy training more consistently than was seen in massed practice. This suggests a possible effect of skills and memory consolidation occurring over time. To optimize technical skills learning, training should be organized as time-distributed practice rather than as a massed block of practice, which is common in skills-training courses. Level of Evidence N/A. Laryngoscope, 126:E74-E79, 2016. © 2015 The American Laryngological, Rhinological and Otological Society, Inc.


Nielsen J.D.,Alexandra Institute | Pagter J.I.,Alexandra Institute | Stausholm M.B.,Alexandra Institute
2012 IEEE International Conference on Pervasive Computing and Communications Workshops, PERCOM Workshops 2012 | Year: 2012

We present a solution which improves the level of privacy possible in location based services (LBS). A core component of LBS is proximity testing of users. Alice wants to know if she is near to Bob (or generally some location). The presented solution support private proximity testing and is actively secure meaning it prevents a number of attacks possible in existing protocols for private proximity testing. We demonstrate that the improved security provided only implies a factor of two penalty on execution time compared to an existing passively secure protocol. We also provide a security analysis and discuss the relevance of secure multiparty computation for location based services. © 2012 IEEE.


Neerbek J.,Alexandra Institute
ACM International Conference Proceeding Series | Year: 2012

Frequent itemset mining finds frequently occurring itemsets in transactional data. This is applied to diverse problems such as decision support, selective marketing, financial forecast and medical diagnosis. The cloud, computation as an utility service, allows us to crunch large mining problems. There are a number of algorithms for doing frequent itemset mining, but none are out-of-the-box suited for the cloud, requiring large data structures to be synchronized across the network. One of the best algorithms for doing frequent itemset mining is the known FP-growth (Frequent Patterns growth). We develop a cloud-enabled algorithmic variant for frequent itemset mining that scales with very little communication and computational overhead and even, with only one worker node, is faster than FP-growth. We develop the concept of a postfix path and show how this allows us to lower the communicational cost and leads to adjustable work sizes. This concept provides a very exible algorithmic solution that can be applied to a wide variety of different problem sizes and setups. Copyright 2012 ACM.

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