Fix Spacingd updating non-metadata entries that share the key prefix

monai/transforms/spatial/dictionary.py

@@ -18,7 +18,7 @@
 from __future__ import annotations
 
 import warnings
-from collections.abc import Hashable, Mapping, Sequence
+from collections.abc import Hashable, Mapping, MutableMapping, Sequence
 from typing import Any, cast
 
 import numpy as np
@@ -523,7 +523,13 @@ def __call__(self, data: Mapping[Hashable, torch.Tensor], lazy: bool | None = No
                 lazy=lazy_,
             )
             if isinstance(d[key], MetaTensor):
-                meta_keys = [k for k in d.keys() if k is not None and k.startswith(f"{key}_")]
+                # only refresh metadata dictionaries (e.g. "image_meta_dict"); other entries that merely
+                # share the prefix (e.g. a string "image_path") must be left untouched
+                meta_keys = [
+                    k
+                    for k in d.keys()
+                    if isinstance(k, str) and k.startswith(f"{key}_") and isinstance(d[k], MutableMapping)
+                ]
                 for meta_key in meta_keys:
                     if "filename_or_obj" in d[key].meta and is_supported_format(
                         d[key].meta["filename_or_obj"], ["nii", "nii.gz"]

tests/transforms/test_spacingd.py

@@ -173,6 +173,22 @@ def test_space_same_shape(self):
         out = Spacingd(("img_1", "img_2"), pixdim=1, ensure_same_shape=False)({"img_1": img_1, "img_2": img_2})
         self.assertNotEqual(out["img_1"].shape, out["img_2"].shape)  # ensure_same_shape False
 
+    def test_meta_dict_updated_for_nifti(self):
+        img = MetaTensor(torch.zeros(1, 8, 8, 8), affine=torch.eye(4), meta={"filename_or_obj": "img.nii.gz"})
+        out = Spacingd("image", pixdim=2.0)({"image": img, "image_meta_dict": {"affine": torch.eye(4)}})
+        # the metadata dict is refreshed from the resampled image (spacing 1 -> 2)
+        assert_allclose(affine_to_spacing(out["image_meta_dict"]["affine"]), (2.0, 2.0, 2.0), type_test=False)
+
+    def test_non_meta_dict_entries_untouched(self):
+        # entries that share the "<key>_" prefix but are not metadata dicts must not be modified (issue #9165)
+        img = MetaTensor(torch.zeros(1, 8, 8, 8), affine=torch.eye(4), meta={"filename_or_obj": "img.nii.gz"})
+        data = {"image": img, "image_path": "img.nii.gz", "image_index": 3, 0: "int key"}
+        out = Spacingd("image", pixdim=2.0)(data)
+        self.assertEqual(out["image_path"], "img.nii.gz")
+        self.assertEqual(out["image_index"], 3)
+        self.assertEqual(out[0], "int key")
+        self.assertEqual(out["image"].shape, (1, 4, 4, 4))
+
 
 if __name__ == "__main__":
     unittest.main()