Move prob_threshold definition to top of file

Relocated the definition of prob_threshold to the top-level scope to avoid redeclaration within the loop and improve code clarity.

Author: markmikkelsen

GannetSegment.m

@@ -44,6 +44,8 @@
 
 run_count = 0;
 setup_spm = 1;
+prob_threshold = 0.9; % threshold to reduce partial volume effect and
+                      % improve accuracy of tissue probability maps
 
 % Loop over voxels if PRIAM
 for kk = 1:length(vox)
@@ -165,8 +167,6 @@
         T1     = spm_vol(struc);
         T1_tmp = T1.private.dat(:,:,:);
 
-        prob_threshold = 0.9; % threshold to reduce partial volume effect and improve accuracy
-
         WM_vol_tmp = WM_vol.private.dat(:,:,:);
         WM_vol_tmp(WM_vol_tmp < prob_threshold) = 0;
         T1_WM = WM_vol_tmp .* T1_tmp;