could someone help to explain why MR pictures flatted why display by MricroN,
some file display nomal,but some file diapay flatted
please
thanks

I am afraid this is an issue with your image and not my software: your image was acquired with anisotropic resolution, e.g. the resolution in plane is much higher than the resolution between slices. If your image stores the true resolution in the header, you can compensate for this artifact by choosing Help/Preferences and then clicking "Reorient images when loading" (it is optional whether you select the rotate to nearest orthogonal). 

You might also want to try MRIcroGL, which should stretch anisotropic images.