Damià Segrelles

Enhancing Privacy and Authorization Control Scalability in the Grid Through Ontologies

The use of data Grids for sharing relevant data has proven to be successful in many research disciplines. However, the use of these environments when personal data are involved (such as in health) is reduced due to its lack of trust. There are many approaches that provide encrypted storages and key shares to prevent the access from unauthorized users. However, these approaches are additional layers that should be managed along with the authorization policies. We present in this paper a privacy-enhancing technique that uses encryption and relates to the structure of the data and their organizations, providing a natural way to propagate authorization and also a framework that fits with many use cases. The paper describes the architecture and processes, and also shows results obtained in a medical imaging platform.

Creating virtual storages and searching DICOM medical images through a grid middleware based in OGSA

Most medical imaging departments of hospital and primary care services in developed countries have migrated in the last years to full digital storing, management and processing. The availability of clinical medical images is larger than ever, but the exploitation of its intrinsic knowledge is poor. Hospitals, clinics and primary care centres store the information locally with a poor degree of interoperability. Although current archiving, flow-control and processing means and protocols of PACS are successful for reporting and patient follow-up, the archiving systems are not designed to exchange interesting cases, to search by medical content or to aggregate epidemiological information. This article presents a Middleware based on Grid Technologies that addresses the problem of sharing, transferring and processing DICOM medical images in a distributed environment. It tackles the problem of incompatibilities by providing a virtual storage that builds-up virtual repositories integrating different individual and incompatible storages providing global searching, progressive transmission, automatic encryption and pseudo-anonimisation and a hook to remote processing services. Users from a virtual organisation can share the cases that arc relevant for their topic of research, epidemiological study or even deeper analysis of a complex individual case. The article describes the architecture, the technologies used, the problems faced and the solutions proposed, and the results in the form of a brief performance analysis and several snapshots.

Service monitoring and differentiation techniques for resource allocation in the grid, on the basis of the level of service

The study of meta-scheduling of jobs in the Grid has been a recurrent topic on the literature. Many tools have been developed for allocating the jobs to the most appropriate resources according to specific application needs while balancing the workload among resources. However, few of them focus on evaluating the level of service attained by providers of Grid services. On the contrary, Grid generally offers best-effort service to all the applications. Without Quality of Service (QoS), the jobs are executed without any guarantee on the execution time or throughput. Also, the support for qualitative attributes, such as security, is limited to the information provided by the resources. The uncertainty on the final performance is an issue that affects user satisfaction, reducing the interest of Grid infrastructures. In this paper, we present GRIDIFF, a software architecture that covers all necessary steps to integrate QoS into the process of allocating resources for the execution of jobs in the Grid. GRIDIFF has been used in practice to differentiate the resources according to the fulfillment of the 100% of the QoS considering three groups with failure rates of 9.1%, 13.3% and 64.1%, respectively. Scalability has been evaluated through simulation in up to 7000 nodes that can handle up to 250 monitoring agents per node.

TRENCADIS – a grid architecture for creating virtual repositories of DICOM objects in an OGSA-Based ontological framework

The creation of virtual repositories of medical data is a very important challenge to ease collaboration, research and training among medical organisations. However, there are several technical and legal problems, such as efficient large data distribution, privacy protection, post-processing and knowledge management. The TRENCADIS project is aiming at the development of an infrastructure able to tackle with such problems using Grid Technologies. This article presents the Grid Software Architecture developed, which is implemented on top of the OGSA specification and defines the mechanisms to create virtual repositories of DICOM objects. It integrates different repositories providing a single-database virtual view through high-level components. The TRENCADIS architecture proposes the use of ontologies and templates to organise the DICOM data of Structured Reports. The TRENCADIS architecture is being used for the development of a cyberinfraestructure for medical imaging on oncology in the land of Valencia, with the participation of seven hospitals.

A framework based on web services and grid technologies for medical image registration

Medical Imaging implies executing complex post-processing tasks such as segmentation, rendering or registration which requires resources that exceeds the capabilities of conventional systems. The usage of Grid Technologies can be an efficient solution, increasing the production time of shared resources. However, the difficulties on the use of Grid technologies have reduced its spreading outside of the scientific arena. This article tackles the problem of using Grid Technologies for the co-registration of a series of volumetric medical images. The co-registration of time series of images is a needed pre-processing task when analysing the evolution of the diffusion of contrast agents. This processing requires large computational resources and cannot be tackled efficiently on an individual basis. This article proposes and implements a four-level software architecture that provides a simple interface to the user and deals transparently with the complexity of Grid environment. The four layers implemented are: Grid Layer (the closest to the Grid infrastructure), the Gate-to-Grid (which transforms the user requests to Grid operations), the Web Services layer (which provides a simple, standard and ubiquitous interface to the user) and the application layer. An application has been developed on top of this architecture to manage the execution of multi-parametric groups of co-registration actions on a large set of medical images. The execution has been performed on the EGEE Grid infrastructure. The application is platform-independent and can be used from any computer without special requirements.

A supporting infrastructure for evaluating QoS-specific activities in SOA-based Grids

Despite the advances that have been made in Grid acceptance and adoption, further efforts are needed to ensure that the required level of service predictability is achieved. QoS issues require close attention, especially those aspects related to the evaluation of specific service activities with the aim of ensuring that the execution of a task produces an outcome according with its expectative behaviour. In this paper we present a supporting infrastructure to enable organisations to tackle the lack of tools for evaluating QoS-specific service activities. Additionally, we describe a case study that illustrates the applicability of the proposed model to general-purpose service management issues. The model has been tested in a controlled environment with promising results.

Introducing High-Performance and High-Throughput Processing in the TRENCADIS Data Sharing Architecture

TRENCADIS (towards a grid environment to process and share DICOM objects) is a data sharing infrastructure based on grid technologies that federate distributed repositories of radiological studies using ontological models on the information of the structured reports. TRENCADIS has demonstrated its efficiency in data sharing. This work describes an extension of the architecture, based on WSRF, to deal with both high-performance and high-throughput applications on medical images. This enables TRENCADIS to work with complex workflows exploiting the computing capabilities of current e-infrastructures, such as EGEE.

Long-term storage and management of encrypted biomedical data in real scenarios

This paper emphasizes the development and application of technologies to effective guarantying the confidentiality and integrity of patient data in Grid-enabled biomedical applications. By strongly focusing on the interaction between security technologies and the human environment, this paper relates the experience of developing a model for the storage and management of encrypted medical data in the Grid. The ideas and concepts behind the proposed solution are briefly explained, as well as the components implementing the model in an OGSA compliant architecture. TRENCADIS, a project for managing DICOM structured reporting objects for use in a Valencian cyberinfrastructure for medical imaging in oncology (CVIMO), is currently adopting the architecture as a core component.

A web-based application service provision architecture for enabling high-performance image processing

The work described in this paper presents a distributed software architecture for accessing high performance and parallel computing resources from web applications. The architecture is designed for the case of medical image processing, although the concept can be extended to many other application areas. Parallel computing algorithms for medical image segmentation and projection are executed remotely through Web services as being local. Ubiquity and security on the access and high performance tools have been the main design objectives. The implementation uses the Application Service Provision model, of increasing importance in the exploitation of software applications. The system is under clinical validation and considers all the industrial and de-facto standards in medical imaging (DICOM, ACR-NEMA, JPEG2000) and distributed processing (CORBA, Web Services, SOAP).