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  • Submission and De-identification Overview

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Private Tags - Unfortunately, there are many cases where vendors do not make the conformance statement for a piece of equipment publicly available or do not adequately define what is stored in the private tags, but these fields are extensively used by DICOM vendors to store information about the scans which are sometimes necessary for researchers to utilize the data. When a submitting site sends DICOM data to TCIA all private tags are retained and then de-identified by TCIA during curation of the data according to the Retain Safe Private Option. The Retain Safe Private Option allows for the retention of DICOM tags stored in the private fields.  TCIA uses a private tag dictionary maintained by the Posda curation toolkit to decide the disposition of a vendor written private tag. The Posda private tag dictionary is a compilation of 4 well-known private tag dictionaries, :

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  • DICOM3tools

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  • DCMTK

The addition of the other 3 private tag dictionaries allows for an expanded set of scientifically useful tags to be retained. To implement the new Posda private tag dictionary, TCIA resolved any discrepancies between the 4 included dictionaries and assigned dispositions to all private tags ever seen by Posda. Unique values seen within the private tags were inspected to ensure that dispositions were correctly assigned.  If a new private tag is encountered in the Posda database that does not have a private tag disposition, values are inspected in relation to the tag description together with values in the tags and a disposition is assigned. If there is no existing private tag description, an attempt is made to find a manufacturer’s definition of the tag. If no such description can be found the disposition is defined to remove the tag. TCIA will remove any private tags from the images that are not specified in the private tag dictionary or are defined as containing a form of PHI such as name, SSN, etc.  All date and datetime private tags that are retained are offset using the same offset as applied to the standard tags for the image. All private tags containing UIDs are assigned a TCIA root and appended with a hashed value as done with the standard tags. This ensures all references to other images contained within TCIA are maintained. A manual inspection of all private tags is performed using tagSniffer reports and any PHI that may be found is removed, emptied, date offset, or hashed as appropriate.

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