Orthanc: a Lightweight, Open-Source DICOM Server for Medical Imaging Informatics

Orthanc is a free and open-source ecosystem designed to lower the barrier to working with medical imaging data in clinical, research, and industrial settings. Built around the DICOM standard, the Orthanc server is distributed as a single executable with no external dependencies. It runs out-of-the-box on all major operating systems and exposes a RESTful API that enables straightforward integration with contemporary Web technologies and custom workflows. Originally developed at the University Hospital of Liège and actively maintained by UCLouvain in an academic setting, Orthanc is now used worldwide as a lightweight PACS (Picture Archiving and Communication System), as middleware for inter-site image exchange, as a substrate for teleradiology, and as a platform for de-identification and artificial intelligence (AI) pipelines. Its plugin architecture allows the core server to be extended with database backends, Web-based viewers, or additional capabilities such as DICOMweb support and whole-slide imaging. A companion project, the Stone Web Viewer, provides a bandwidth-efficient Web viewer built on WebAssembly. Recognised as a Digital Public Good, Orthanc integrates with open-source electronic health record systems and benefits from an active worldwide community. The mission of the Orthanc project is to make technological knowledge about medical imaging freely accessible to any institution, regardless of size or means