With the advent of digital imaging technology and the implementation of electronic patient records, the vast amount of online information has exceeded any human processing capability. This information "overload" challenges hospital information systems, meanwhile provides unprecedented opportunities for decision support to healthcare professionals and patients alike. In Healthcare domain, knowledge is represented in all formats and generated from all sources. The medical knowledge bases are diverse, with many details, relationships, and sometimes uncertainties. Semantic Web technology provides a universal framework for connecting information semantically and unambiguously. In this work, a semantic webized ontology(RPGOntology) is developed based on the EU Referral Guideline for Imaging [1]. Written in RDF [2] and OWL [3], it can be consumed by any generic reasoning engines for semantic web. Test cases include using RPGOntology to validate radiological orders and find recommendations for a given medical condition. Issues regarding clinical validation and evolving of RPGOntology are also discussed.