Merge pull request #484 from nipreps/enh/syn-laplacian-weight

ENH: Allow changing laplacians weights in SyN registration metric

Author: oesteban

sdcflows/data/sd_syn.json

@@ -5,7 +5,7 @@
     "dimension": 3,
     "interpolation": "Linear",
     "metric": [ ["Mattes", "Mattes"], ["Mattes", "Mattes"] ],
-    "metric_weight": [ [0.5, 0.5], [0.5, 0.5] ],
+    "metric_weight": [ [0.9, 0.1], [0.8, 0.2] ],
     "number_of_iterations": [ [ 200, 100 ], [ 10 ] ],
     "output_transform_prefix": "fmap_syn",
     "radius_or_number_of_bins": [ [48, 48], [48, 48] ],

sdcflows/data/sd_syn_sloppy.json

@@ -5,7 +5,7 @@
     "dimension": 3,
     "interpolation": "Linear",
     "metric": [ ["Mattes", "Mattes"], ["Mattes", "Mattes"] ],
-    "metric_weight": [ [0.5, 0.5], [0.5, 0.5] ],
+    "metric_weight": [ [0.9, 0.1], [0.8, 0.2] ],
     "number_of_iterations": [ [ 20, 10 ], [ 2 ] ],
     "output_transform_prefix": "fmap_syn",
     "radius_or_number_of_bins": [ [48, 48], [48, 48] ],

sdcflows/workflows/fit/syn.py

@@ -39,6 +39,7 @@
     "anat_mask",
     "sd_prior",
 )
+MAX_LAPLACIAN_WEIGHT = 0.5
 
 
 def init_syn_sdc_wf(
@@ -48,6 +49,7 @@ def init_syn_sdc_wf(
     debug=False,
     name="syn_sdc_wf",
     omp_nthreads=1,
+    laplacian_weight=None,
     sd_prior=True,
     **kwargs,
 ):
@@ -82,6 +84,11 @@ def init_syn_sdc_wf(
         Name for this workflow
     omp_nthreads : :obj:`int`
         Parallelize internal tasks across the number of CPUs given by this option.
+    laplacian_weight : :obj:`tuple` (optional)
+        Tuple of two weights of the Laplacian term in the SyN cost function (one weight per
+        registration level).
+    sd_prior : :obj:`bool`
+        Enable using a prior map to regularize the SyN cost function.
 
     Inputs
     ------
@@ -229,6 +236,16 @@ def init_syn_sdc_wf(
     syn.inputs.output_warped_image = debug
     syn.inputs.output_inverse_warped_image = debug
 
+    if laplacian_weight is not None:
+        laplacian_weight = (
+            max(min(laplacian_weight[0], MAX_LAPLACIAN_WEIGHT), 0.0),
+            max(min(laplacian_weight[1], MAX_LAPLACIAN_WEIGHT), 0.0),
+        )
+        syn.inputs.metric_weight = [
+            [1.0 - laplacian_weight[0], laplacian_weight[0]],
+            [1.0 - laplacian_weight[1], laplacian_weight[1]],
+        ]
+
     if debug:
         syn.inputs.args = "--write-interval-volumes 2"