http://teem.sourceforge.net/ 
- unu.exe program link here
128^3 = 2 mega pixel
256^3 = 16 mega pixel
512^3 = 134 mega pixel
dug9 note your source2/teem folder, the NrrdIO is a static .lib 
- and gradient is a little command line utility to process an nrrd image into a gradient foo.nrrd (folder below)
Not done: ISMRMRD format for MRI data
https://onlinelibrary.wiley.com/doi/10.1002/mrm.26089 
https://github.com/ismrmrd/ismrmrd/tree/master/libsrc