diff --git a/siena_flow2tal b/siena_flow2tal
index 49a916133af844ab8eb24724076cf2a5f3bd38ac..0296d4b6e04b74a2bfed9effd47f50c2007e85ba 100755
--- a/siena_flow2tal
+++ b/siena_flow2tal
@@ -4,7 +4,7 @@
 #
 #   Stephen Smith, FMRIB Image Analysis Group
 #
-#   Copyright (C) 2002-2004 University of Oxford
+#   Copyright (C) 2002-2005 University of Oxford
 #
 #   SHCOPYRIGHT
 
@@ -49,6 +49,9 @@ ${FSLDIR}/bin/convert_xfm -omat ${A}_halfwayto_${B}_to_tal.mat -concat ${A}_to_t
 
 # dilate flow image, -> standard space -> mask with ss edge image -> blur -> remask
 ${FSLDIR}/bin/avwmaths ${A}_to_${B}_flow -dil -dil -dil -dil -dil -dil -dil -dil -dil -dil -dil -dil -dil -dil ${A}_to_${B}_flow_dil
+${FSLDIR}/bin/avwmaths ${B}_to_${A}_flow -dil -dil -dil -dil -dil -dil -dil -dil -dil -dil -dil -dil -dil -dil ${A}_to_${B}_flow_dilback
+${FSLDIR}/bin/avwmaths ${A}_to_${B}_flow_dil -sub ${A}_to_${B}_flow_dilback -div 2 ${A}_to_${B}_flow_dil
+/bin/rm ${A}_to_${B}_flow_dilback*
 ${FSLDIR}/bin/flirt -in ${A}_to_${B}_flow_dil -ref ${FSLDIR}/etc/standard/avg152T1_brain -out ${A}_to_${B}_flow_to_tal -applyxfm -init ${A}_halfwayto_${B}_to_tal.mat
 ${FSLDIR}/bin/avwmaths ${A}_to_${B}_flow_to_tal -mas ${FSLDIR}/etc/standard/avg152T1_edges ${A}_to_${B}_flow_to_tal
 ${FSLDIR}/bin/ip ${A}_to_${B}_flow_to_tal ${A}_to_${B}_flow_to_tal 0 -s 10