HealthGrid 2006 (http://valencia2006.healthgrid.org) is the fourth edition of this open forum for the integration of Grid Technologies and its Applications in the Biomedical, Medical and Biological domains to pave the path to an International Research Area in HealthGrid. The main objective of HealthGrid conference and the HealthGrid Association is the exchange and discussion of ideas, technologies, solutions and requirements that interest the Grid and the Life-Sciences communities to foster the integration of Grids into Health. Participation is encouraged for Grid middleware and Grid applications developers, Biomedical and Health Informatics users and security and policy makers to participate in a set of multidisciplinary sessions with a common concern on the applications to Health.

HealthGrid conferences have been organized in an annual basis. The first conference, held in 2003 in Lyon (http://lyon2003.healthgrid.org), reflected the need to involve all actors – physicians, scientists and technologists – who might play a part in the application of Grid technology to Health, whether health care or bio-medical research. The second conference, held in Clermont-Ferrand in January 2004 (http://clermont2004.healthgrid.org) reported research and work in progress from a large number of projects. The third conference of Oxford (http://oxford2005.healthgrid. org) had a major concern on the results and deployment strategies in Healthcare. Finally, this issue aims at consolidating the collaboration among Biologists, Healthcare professionals and Grid Technology experts.

The conference includes a number of high-profile keynote presentations complemented by a set of high quality refereed papers. The number of contributions to this conference has increased from previous editions, reaching the number of 44 submissions of papers and demos from principal authors coming from 14 countries (according to the number of contributions: France, United Kingdom, Spain, Italy, Germany, Greece, The Netherlands, Belgium, Czech Republic, Cuba, Japan, Romania, Russia and Taiwan). Considering the affiliations of all the authors of the papers, the number of contributing countries is extended to 18 countries including Switzerland, Austria, Turkey and USA. The contributions of this edition follow mainly five main topics: Medical Imaging on the Grid; Ethical, Legal and Privacy Issues on HealthGrids; Bioinformatics on the Grid; Knowledge Discovery on HealthGrids and Medical Assessment and HealthGrid Applications. The maturity of the discipline of HealthGrids is clearly reflected on these subjects. There are more contributions related to two main application areas (Medical Imaging and Bioinformatics), confirming the analysis of the HealthGrid White Paper published last year, which outlined them as the two more promising areas for HealthGrids. Along with these two areas, the assessment on the results of HealthGrid applications, also focused by several contributions, denotes also the maturity of HealthGrids. Finally the other two areas (Knowledge Discovery and Ethical, Legal and Privacy Issues) focus on basic technologies which are very relevant for HealthGrids.

In Medical Imaging, the different contributions covered the problems of medical image processing and virtual distributed storages. In this topic there are contributions focusing on the structuring of medical information through semantic classifications, as in the case of the NeuroBase project presented by Barillot et al. or in the case of the TRENCADIS software architecture presented by Blanquer et al. The problem of encryption and data sharing is a very important topic addressed in contributions such as the Medical Data Manager (Montagnat et al.) and other contributions related with privacy. In the area of medical image processing several papers describe their experiences on providing services for neuroimaging. The work of Olabarriaga et al. cover image processing services for FMRI (Functional Magnetic Resonance Imaging), and Bagnasco et al. describe the application of Grid for the early diagnosis of Alzheimer's disease by assisting the diagnosis on PET / SPECT through Statistical Parametric Mapping and on the highly-computational problem of Fibre Tracking (Bucur et al.). On the area of modelling processes related with medical images, Bellet et al. proposes a web interface for MRI devices simulation, and Blanquer et al. proposes a Grid implementation of processing services for co-registration of medical images for assessing a quantitative diagnosis of liver cancer. In this precise topic of image co-registration, Montagnat et al. propose a mechanism to evaluate the quality of co-registration methods using the Grid, in a methodology called “Bronze Standard”. Finally, the problem of interactive use of Grids for medical image processing is tackled in the work of Germain-Renaud et al.

In the area of Ethical, Legal and Privacy Issues on HealthGrids, on one side, contributions focus on ethical and legal issues, such as the problem of medical consent (Herveg et al.) and the organisation of Virtual Organisations for clinical trials in epidemiology (Sinnott et al.). On the other side, different technical solutions for privacy enhancement are presented. In the work of Torres et al., a solution for sharing an en- crypted and distributed storage of medical images is presented. A similar approach is used by Blanchet et al. to propose a mechanism for encrypting genetic information. Other approaches for sharing and linking for distributed repositories of epidemiological data are presented in Ainsworth et al. and Tashiro et al.

The area of Bioinformatics is a very active one in HealthGrids. The increasing on size and complexity of genomic databases and protein modelling is opening the door to new Grid applications. Results in large-scale in-silico docking for malaria is presented in Jacq et al. and a grid-enabled protein structure prediction system namely Rokky-G is presented in the work of Masuda et al. Other important activity on this topic is the integration of bioinformatics information where the complexity of browsing data is also considered by Schroeder et al. in the frame of the Sealife project. Other approach based in data mediation is presented by Colonna et al. for predisposition Genes discovery. The integration of OGSA-DAI technologies for biochemical distributed data is proposed in Tverdokhlebov et al. The development of genomic processing services and its interfacing to Grid is presented in the porting of the GPS@ portal (Blanchet et al.), and in the work of Segrelles et al., in which an MPIBlast processing Grid service is developed and integrated in a Gene Annotation tool (Blast2GO). The early results of the BIOINFOGRID project are presented in the work of Milanesi et al. More consolidated results on bioprofiling are presented on the work of Sun et al. in the frame of the BIOPATTERN project. Finally, an application of HealthGrid to SARS is described in the work of Hung et al.

In the area of Knowledge Discovery on HealthGrids, contributions focus on the semantic integration of medical information. The work of Boniface et al., in the frame of the ARTEMIS project, focus on Healthcare data, whereas the work of Koutkias et al. focus on semantic integration of bioinformatics data. The semantic integration is the key for knowledge discovery in large databases, in which techniques such as Data Mining are applied. Tsiknakis et al. propose the use of these techniques for cancer study on the ACGT IP, and McClatchey et al. apply those techniques for the integration of paediatric information in the frame of the Health-e-child project.

In the area of Medical Assessment and HealthGrid Applications, covers, on one side, medical results of the application of Grid technologies to Health and other applications related to biomedical simulation and clinical environments. The application of Grids to radiotherapy is also a classic topic due to the maturity of High Energy Physics, revealing new applications of the MonteCarlo simulation to Intensity-Modulated Radiation Therapy (Gómez et al.) and interfacing to well-known environments such as GATE (Thiam et al.). Other applications of P2P and Grid technologies show their potential for emergency management (Harrison et al.), and collaborating environments (Kuba et al.). Finally, contributions also focus on the needs of hospital management systems for Grids (Graschew et al.), the success stories of e-DiaMoND and NeuroGrid projects (Ure et al.) and the exploitation of successful projects on Medical Imaging and Grids, such as the MAMMOGRID project (del Frate et al.).