The DICOM Anonymizer Keep Safe Private Elements Feature

This article describes how to use the DICOM anonymizer Keep Safe Private Elements feature. The intended audience for this information is clinical trial coordinators at principal investigator sites.

Mallinckrodt Institute of Radiology maintains a list of private elements on behalf of the National Cancer Institute.

The DICOM Anonymizer contains an internal index of safe private elements based on the Mallinckrodt list. The DICOM Anonymizer Configurator has a "Keep safe private elements" checkbox that invokes the feature. The line appears at the end of the list of global keep commands near the bottom of the configurator window.

New installations and upgrades contain updated default anonymizer scripts that include the "Keep safe private elements" command, but it is deselected for backward compatibility.

Upgrades do not automatically add the command to existing scripts. To add the command to an existing script, use the Edit menu in the configurator. After adding the command to a script, its checkbox must be selected to enable it.

The standard dictionary of private elements is contained in the CTP/libraries/CTP.jar file. This file can be opened by any Zip utility. The file is located in the root of the zip tree. It is called PrivateTagDictionary.xml. The schema has this form:

<?xml version="1.0" encoding="UTF-8"?>
<dictionary>
    <elements type="Private">
        <element
            code="X"
            cr="BrainWave: 1.2.840.113819.3"
            el="11"
            file="Discovery_MR.xlsx [sheet1.xml]"
            gp="1001"
            key="DICOMImplementationVersion"
            src="MIR"
            vm="1"
            vr="SH"/>
        <element
            code="X"
            cr="BrainWave: 1.2.840.113819.3"
            el="10"
            file="Discovery_MR.xlsx [sheet1.xml]"
            gp="2001"
            key="DICOMImplementationUID"
            src="MIR"
            vm="1"
            vr="UI"/>
        <element
            code="X"
            cr="BrainWave: 1.2.840.113819.3"
            el="12"
            file="Discovery_MR.xlsx [sheet1.xml]"
            gp="2001"
            key="WithinDICOMImplementationSOPInstanceUID"
            src="MIR"
            vm="1"
            vr="UI"/>
        etc.
    </elements>
</dictionary>

The important attributes are:

• gp: the group number (four hex characters)
• cr: the private creator (the block owner)
• el: the element number (two hex characters)
• code: the action code (defined in DICOM PS 3.15 Appendix E)

In the current implementation, only those private elements whose code attribute is K are considered safe.

The other attributes are not used by the Keep Safe Private Elements feature; they are included in the dictionary for documentation.

A local site can extend the dictionary by creating a file of the same name and placing it in the CTP directory. The local file is loaded after the standard file, so it can add to or overwrite elements in the standard index. This capability is only needed if the local site uses private elements not in the standard dictionary, and elements in the standard dictionary do not have to be included in the local dictionary unless the code attribute must be changed. If changes are made in the local file, CTP must be restarted for them to take effect.

In a local dictionary, only the four important attributes are required to be supplied for each element, but it is highly recommended that the vr and vm attributes also be supplied for future use in the DicomCorrector pipeline stage.