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bug: Fix field removal and blanking to clean up child UID references #293

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Merged
vsoch merged 2 commits into from
Dec 2, 2025
Merged

bug: Fix field removal and blanking to clean up child UID references #293

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d911d72
bug: Fix field removal and blanking to clean up child UID references
Simlomb Nov 17, 2025
9ecfb9b
feat: add get_child_fields to list child fields UIDs, bump version an…
Simlomb Nov 24, 2025
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24 changes: 22 additions & 2 deletions deid/dicom/parser.py
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Original file line number Diff line number Diff line change
Expand Up @@ -181,22 +181,42 @@ def delete_field(self, field):
Delete a field from the dicom.

We do this by way of parsing all nested levels of a tag into actual tags,
and deleting the child node.
and deleting the child node. If the field being deleted has nested children
(e.g., a sequence), also remove all child field UIDs from the internal lookup.
"""
# Returns the parent, and a DataElement (indexes into parent by tag)
parent, desired = self.get_nested_field(field, return_parent=True)
if parent and desired in parent:
del parent[desired]
# Remove the field itself from the lookup
self.fields.remove(field.uid)
# Also remove any child fields that were nested under this field
field_uid_prefix = field.uid + "__"
child_uids = [
uid for uid in self.fields if uid.startswith(field_uid_prefix)
]
for child_uid in child_uids:
self.fields.remove(child_uid)

def blank_field(self, field):
"""
Blank a field
Blank a field.

If the field being blanked has nested children (e.g., a sequence),
also remove all child field UIDs from the internal lookup since they
become inaccessible after blanking the parent.
"""
# Returns the parent, and a DataElement (indexes into parent by tag)
parent, desired = self.get_nested_field(field, return_parent=True)
if parent and desired in parent:
parent[desired].value = None
# Also remove any child fields that were nested under this field
field_uid_prefix = field.uid + "__"
child_uids = [
uid for uid in self.fields if uid.startswith(field_uid_prefix)
]
for child_uid in child_uids:
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@vsoch vsoch Nov 21, 2025

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A few comments. When we blank a field, it technically is still there (just blank) so why would we remove it (and child fields) here? Also, if there is shared logic between these functions to derive and yield child fields, we might instead have a shared function:

for child_uid in self.yield_child_fields(field):
    # do action(s)

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@Simlomb Simlomb Nov 24, 2025

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A few comments. When we blank a field, it technically is still there (just blank) so why would we remove it (and child fields) here?

When a parent field is blanked that tag has zero length, hence there are no more child tags. The error raised because the uid lookup still listed those nested tags with other actions, even when they did not exist anymore in the dicom file. In those new lines we do not remove the tags from the dicom files, but just from the field lookup.

Also, if there is shared logic between these functions to derive and yield child fields, we might instead have a shared function:

for child_uid in self.yield_child_fields(field):
    # do action(s)

Thanks for catching that, I added the new method. I also bumped the version and changelog. Let me know if you have any other comments.

self.fields.remove(child_uid)

def replace_field(self, field, value):
"""
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76 changes: 76 additions & 0 deletions deid/tests/test_action_interaction.py
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Expand Up @@ -1865,6 +1865,82 @@ def test_remove_remove_should_remove(self):
with self.assertRaises(KeyError):
_ = outputfile[field].value

def test_remove_parent_tag_replace_child_with_no_conflict(self):
"""RECIPE RULE
REMOVE (0032,1064) Requested Procedure Code Sequence
REPLACE (0008,0104) "Anonymized"
"""
print(
"Test REMOVE standard sequence tag and REPLACE child tag should not cause conflict"
)
dicom_file = get_file(self.dataset)

field1 = "(0032,1064)"
action1 = "REMOVE"
action2 = "REPLACE"
value2 = "Anonymized"
field2 = "(0008,0104)"
field_dicom1 = "00321064"
field_dicom2 = "00080104"

actions = [
{"action": action1, "field": field1},
{"action": action2, "field": field2, "value": value2},
]
recipe = create_recipe(actions)

result = replace_identifiers(
dicom_files=dicom_file,
deid=recipe,
save=True,
remove_private=False,
strip_sequences=False,
)
outputfile = utils.dcmread(result[0])

self.assertEqual(1, len(result))
with self.assertRaises(KeyError):
_ = outputfile[field_dicom1].value
_ = outputfile[field_dicom1][0][field_dicom2].value

def test_blank_parent_tag_remove_child_with_no_conflict(self):
"""RECIPE RULE
BLANK (0032,1064) Requested Procedure Code Sequence
REPLACE (0008,0104) "Anonymized"
"""
print(
"Test BLANK standard sequence tag and REPLACE child tag should not cause conflict"
)
dicom_file = get_file(self.dataset)

field1 = "(0032,1064)"
action1 = "BLANK"
action2 = "REPLACE"
value2 = "Anonymized"
field2 = "(0008,0104)"
field_dicom1 = "00321064"
field_dicom2 = "00080104"

actions = [
{"action": action1, "field": field1},
{"action": action2, "field": field2, "value": value2},
]
recipe = create_recipe(actions)

result = replace_identifiers(
dicom_files=dicom_file,
deid=recipe,
save=True,
remove_private=False,
strip_sequences=False,
)
outputfile = utils.dcmread(result[0])

self.assertEqual(1, len(result))
self.assertEqual(len(outputfile[field_dicom1].value), 0)
with self.assertRaises(IndexError):
_ = outputfile[field_dicom1][0][field_dicom2].value


if __name__ == "__main__":
unittest.main()