VirtualPACS opens Grid access to imaging resources

Despite wide adoption of the DICOM standard, sharing digital imaging data across institutions can still be a challenge. Too often, the radiology community relies on slower, less efficient means such as CDs and U.S. mail to transfer imaging data between interested parties. A better solution to sharing DICOM data over the Internet has surfaced at Ohio State University. Researchers there are proposing a mechanism called VirtualPACS that allows users to access remote imaging data as if the images were stored in a centralized PACS."Using the VirtualPACS toolkit, users can perform standard DICOM query, retrieve, and submit functions across distributed image databases," said Ashish Sharma, Ph.D., of the OSU biomedical informatics department. The distributed data can be either native DICOM sources, such as PACS servers, or non-native DICOM sources: images in the National Cancer Imaging Archive, the American College of Radiology Imaging Network, and Quality Assurance Review Center."This means that VirtualPACS federates multiple remote data sources, including those that do not support DICOM messaging, and presents them to a DICOM client as a single virtual resource -- a virtual PACS," Sharma said. This work has the potential to become a key to enhancing multi-institutional collaborations in biomedical imaging studies, he said.

The VirtualPACS framework consists of three layers:

• the presentation layer provides a gateway between local DICOM clients and remote image data and converts DICOM requests into appropriate Grid requests
• the middleware layer provides tools, runtime support, and services for secure access to data resources
• the mediation layer implements tools for mapping various backend image databases to a common set of interfaces and data models to image data can be federated and accessed remotely within VirtualPACS

Security is handled by a caGrid security infrastructure called GAARDS. This package enables federation of user credentials, distributed role-based access control, secure and encrypted data transfer, and management of a trust fabric.

"GAARDS provides single sign-on. It can use an individual's institutional identity or a Grid-based virtual organization identity to generate a Grid credential used for authenticating and authorizing a user across the Grid," Sharma said. Researchers are currently developing extensions that will support other DICOM objects, such as structured reports and work lists."We are also developing security plug-ins that will leverage DICOM security for transactions between a DICOM client and the presentation layer of VirtualPACS," he said.VirtualPACS

software

is publicly available. Operational details can also be found in the

Journal of Digital Imaging

(2007 Sep 18; [Epub ahead of print]).