Check size of decompressed sinograms

[bathomas]

nm_validate deliberately does not check the size of a sinogram due to compression. Should check if sinogram is compressed, and if not, check the size.

[bathomas]

nm_validate assumes there will be a DICOM header available. The decompressed mMR sinogram is in Interfile format. So either this means adding (rudimentary) Interfile support or perhaps re-using the parser in STIR.