The Digital Imaging and Communications in Medicine (DICOM) standard defines Radiology medical device interoperability and image data exchange between modalities, image databases - Picture Archiving and Communication Systems (PACS) - and image review end-points. However the scope of DICOM and PACS technology is currently limited to the trusted and static environment of the hospital. In order to meet the demand for ad-hoc tele-radiology and image guided medical procedures within the global healthcare enterprise, a new technology must provide mobility, security, flexible scale of operations, and rapid responsiveness for DICOM medical devices and subsequently medical image data. Grid technology, an informatics approach to securely federate independently operated computing, storage, and data management resources at the global scale over public networks, meets these core requirements. Here we present an approach to federate DICOM and PACS devices for large-scale medical image workflows within a global healthcare enterprise. The Globus MEDICUS (Medical Imaging and Computing for Unified Information Sharing) project uses the standards-based Globus Toolkit Grid infrastructure to vertically integrate a new service for DICOM devices – the DICOM Grid Interface Service (DGIS). This new service translates between DICOM and Grid operations and thus transparently extends DICOM to Globus based Grid infrastructure. This Grid image workflow paradigm has been designed to provide not only solutions for global image communication, but fault-tolerance and disaster recovery using Grid data replication technology. Actual use-case of 40 MEDICUS Grid connected international hospitals of the Childerns Oncology Group and the Neuroblastoma Cancer Foundation and further clinical applications are discussed. The open-source Globus MEDICU http://dev.globus.org/wiki/Incubator/MEDICUS.