Amide's a Medical Imaging Data Examiner (AMIDE) is a completely free tool for viewing, analysing, and registering volumetric medical imaging data sets. It's been written on top of GTK+ , and runs on any system that supports this toolkit (Linux, Windows, Mac OS X with fink, etc.).
You can use the category filters given on the right sidebar to narrow down your search results.
Rad is a DICOM workstation written in Cocoa for MacOSX. Using QuickTime, OpenGL, and open source databases iRad aims to provide an easy and efficient way to review medical images from CT, MRI, ultrasound, and other DICOM sources such as angiography.
The goal of OpenIGTLink is to provide a standardized mechanism to connect software/hardware through the network for image-guided therapy (IGT) applications. The features of OpenIGTLink include:
3D Slicer is an open source software platform for medical image informatics, image processing, and three-dimensional visualization. Built over two decades through support from the National Institutes of Health and a worldwide developer community, Slicer brings free, powerful cross-platform processing tools to physicians, researchers, and the general public.