OsiriX is an image processing application for the Apple MacOS operating system dedicated to DICOM images (".dcm" / ".DCM" extension) produced by equipment (MRI, CT, PET, PET-CT, ...). OsiriX is complementary to existing viewers, in particular to nuclear medicine viewers. It can also read many other file formats: TIFF (8,16, 32 bits), JPEG, PDF, AVI, MPEG and QuickTime. It is fully compliant with the DICOM standard for image communication and image file formats. OsiriX is able to receive images transferred by DICOM communication protocol from any PACS or medical imaging modality (STORE SCP - Service Class Provider, STORE SCU - Service Class User, and Query/Retrieve). Since 2010, a commercial version of OsiriX, named "OsiriX MD", is available. Its original source code is still available on GitHub. A demo version, "OsiriX Lite", still remains available free of charge with some limitations. History The OsiriX project started in 2004 at UCLA with Dr Antoine Rosset and Prof. Osman Ratib. OsiriX has been developed by Rosset, working in LaTour Hospital (Geneva, Switzerland) and Joris Heuberger, a computer scientist from Geneva. In 2010, a version of OsiriX for iPhone and iPod touch was released. In early 2015, the healthcare software company Purview forked OsiriX 5.9 to create the open-source Horos viewer, which added 64-bit capability and removed various limitations of OsiriX Lite. Horos was initially licensed under the GNU GPL license due to incomplete license information in the OsiriX source code, but this was subsequently modified to the GNU LGPL license to align with the intended OsiriX licensing. Horos and OsiriX Lite continue to share comparable feature sets. Features OsiriX has been specifically designed for navigation and visualization of multimodality and multidimensional images: 2D Viewer, 3D Viewer, 4D Viewer (3D series with temporal dimension, for example: Cardiac-CT) and 5D Viewer (3D series with temporal and functional dimensions, for example: Cardiac-PET-CT). The 3D Viewer offers all modern rendering modes: Multiplanar reconstruction (MPR), Surface Rendering, Volume Rendering and Maximum intensity projection (MIP). All these modes support 4D data and are able to produce image fusion between two different series (for example: PET-CT). OsiriX is simultaneously a DICOM PACS workstation for imaging and an image processing software package for research (radiology and nuclear imaging), functional imaging, 3D imaging, confocal microscopy and molecular imaging. OsiriX supports a complete plug-in architecture that allows one to expand the capabilities of OsiriX for personal needs. OsiriX is released under a proprietary