Merge pull request #400 from MRtrix3/5tt_documentation_additions

ACT: minor changes to documentation

Author: Lestropie

cmd/5ttgen.cpp

@@ -45,7 +45,8 @@ void usage ()
 	AUTHOR = "Robert E. Smith (r.smith@brain.org.au)";
 
   DESCRIPTION
-  + "concatenate segmentation results from FSL FAST and FIRST into the 5TT format required for ACT";
+  + "concatenate segmentation results from FSL FAST and FIRST into the 5TT format required for ACT"
+  + "Note: if you need to add a pathological tissue mask, use the 5ttedit command.";
 
   ARGUMENTS
   + Argument ("in_fast_one",   "first output PVE image from FAST (should be CSF)").type_image_in()

src/dwi/tractography/ACT/act.cpp

@@ -58,7 +58,7 @@ namespace MR
         void verify_5TT_image (const Image::Header& H)
         {
           if (!H.datatype().is_floating_point() || H.ndim() != 4 || H.dim(3) != 5)
-            throw Exception ("Image " + H.name() + " is not a valid ACT 5TT image");
+            throw Exception ("Image " + H.name() + " is not a valid ACT 5TT image (expecting 4D image with 5 volumes and floating-point datatype)");
         }