Currently, most medical information is scattered across diverse independent information systems, such as Hospital Information System (HIS), Picture Archiving and Communication System (PACS), and other medical databases, with varying degree of interconnectivity and data integration. In this environment, our objective is to collate text data, mostly in HIS, with relevant image data, mostly in PACS, transparently from different local sources and have them as a logically integrated whole. Even though there has been much research on designing PACS DBs and discussing issues of data integration, very few have addressed the dynamic nature of data integration in the context of medical informatics. With various reasons including security, it is desirable for a user to be able to create an integrated view based on data semantics, given data range, and security classification. In addition, the integrity of the integrated view should be maintained even with the local schema changes. In order to accomplish these capabilities, generic tools which can perform semi-automated integration of information have to be developed. In this paper, we will discuss the technical background regarding data integration of different local PACS DBs and HIS. Also, based on the integrated-view (or schema), several aspects of query processing are discussed.