Stone of Orthanc is a lightweight, cross-platform C++ toolkit for the CPU-based rendering of medical images. It notably features support for MPR (multiplanar reconstruction of volume images), PET-CT fusion, and accurate physical world coordinates. Stone of Orthanc is not a fully-featured DICOM viewer, but rather a building block to create such applications.
Stone of Orthanc comes bundled with its own software-based rendering engine (based upon cairo). This engine will use CPU hardware acceleration, but not the GPU. This makes Stone a highly versatile framework that can run even on low-performance platforms. Stone is able to display DICOM series without having to entirely store them in the RAM.