A diffusion MRI analysis tool 
DSI Studio is an open-source diffusion MRI analysis tool that maps brain connections and correlates findings with neuropsychological disorders. It is a collective implementation of several methods, including DTI, QBI, DSI, generalized q-sampling imaging, q-space diffeomorphic reconstruction, diffusion MRI connectometry, and generalized deterministic fiber tracking. Its fiber tracking method has achieved the highest "valid connection" examined by an open competition (see the valid connection achieved by ID:03 at 

Scientific impact
DSI Studio has been applied to human and animal studies and facilitated many peer-review journal publications. In the year of 2015 alone, DSI Studio has facilitated 50 peer-reviewed journal publications (see Citations for details). The following figures are from these publications.

Fig. B has been adopted in Fornito A et al., Nat Rev Neurosci, 2015. 16(3): p. 159-72 (Box 1B), originally published in PLoS ONE 8(11): e80713. 2013.
Cerebral Cortex, 2013 Oct;23(10):2347-56     PLoS ONE 9(4): e93344. , 2014      
PLoS ONE 8(11): e80713. 2013

Open source, open file format
DSI Studio is open source. The file format used in DSI Studio can be loaded/save from MATLAB, giving users the greatest flexibility to process the data. DSI Studio supports DICOM file format, Bruker 2dseq, and 4D NIFTI. It was designed to work with other popular tools such as FSL, TrackVis.