3D Slicer

3D Slicer is a free, open-source platform for medical image computing: it handles visualization, segmentation, registration, and analysis of 3D biomedical data.

3D Slicer is the premier modular, open-source software package (BSD-style license) for advanced medical image analysis and scientific visualization. Built on robust frameworks like VTK and ITK, the platform provides core tools for segmentation, registration, and quantification of multimodal data, including DICOM and meshes. It supports a vast array of clinical research applications: neurosurgery, prostate cancer, and orthopedic biomechanics, for example. The architecture is highly extensible, offering over 150 community-developed extensions, and features a C++ core with a powerful Python API for rapid development and deployment of custom solutions.

https://www.slicer.org