MRIcroGL
-Drag a brain template image (eg mni152_2009_256.nii)
-Overlays>add overlay> select the contrast.hdr you want (eg t image)
Shader drop down: simple
Table: color: 1hot; change the min max (according to the image, eg t values; if it's a negative contrast then enter negative values)
Color> back color> white
Color> colorbar> visible
Display> render, then play with depth, azimuth, elevation sliders to get the right angle
Overlays> transparency on background: 0% opaque
Overlays> transparency on other background> 50%