Fix NiftiDataWriter spacing handling for 1mm pixel dimensions

Signed-off-by: Simone Bendazzoli <simben@kth.se>

Author: SimoneBendazzoli93

monai/deploy/operators/nii_data_writer_operator.py

@@ -70,8 +70,11 @@ def convert_and_save(self, seg_image, nii_path):
         """
         image_writer = SimpleITK.ImageFileWriter()
 
+        pixdim = seg_image.metadata()["pixdim"]
+        if pixdim[0] == 1:
+            pixdim = np.array(pixdim[1:4])
         image = SimpleITK.GetImageFromArray(seg_image._data)
-        image.SetSpacing(seg_image.metadata()["pixdim"])
+        image.SetSpacing(pixdim)
 
         if len(seg_image.metadata()["direction"]) == 16:
             direction = []