Longitudinal Temporal Information Modified Attribute
| Tag | (0028,0303) |
|---|---|
| Type | Optional (3) |
| Keyword | LongitudinalTemporalInformationModified |
| Value Multiplicity | 1 |
| Value Representation | Code String (CS) |
| Example Values |
|
Indicates whether or not the date and time Attributes in the Instance have been modified during de-identification.
Enumerated Values:
- UNMODIFIED
-
- MODIFIED
-
- REMOVED
-
See Section E.2 “Basic Application Level Confidentiality Profile” in PS3.15 and Section E.3.6 “Retain Longitudinal Temporal Information Options” in PS3.15 .
Section E.2 “Basic Application Level Confidentiality Profile” in PS3.15
E.2 Basic Application Level Confidentiality Profile
This Profile is intended for use in clinical trials, and other scenarios in which de-identification may be required, such as creation of teaching files, other types of publication, as well as submission of images and associated information to registries, such as oncology or radiation dose registries.
This Basic Application Level Confidentiality Profile defines an extremely conservative approach that removes all information related to:
-
the identity and demographic characteristics of the patient
-
the identity of any responsible parties or family members
-
the identity of any personnel involved in the procedure
-
the identity of the organizations involved in ordering or performing the procedure
-
additional information that could be used to match instances if given access to the originals, such as UIDs, dates and times
-
Private Attributes
when that information is present in the non-Pixel Data Attributes, including graphics or overlays, as described in Table E.1-1.
Note
Unless the Clean Pixel Data Option or the Clean Recognizable Visual Features Option is specified, this Profile does not address information in the pixels.
The Attribute Longitudinal Temporal Information Modified (0028,0303) shall be added to the Dataset with a Value of "REMOVED" if none of the Retain Longitudinal Temporal Information Options is applied.
Section E.3.6 “Retain Longitudinal Temporal Information Options” in PS3.15
E.3.6 Retain Longitudinal Temporal Information Options
Dates and times are recognized as having a potential for leakage of identity because they constrain the number of possible individuals that could be the imaging subject, though only if there is access to other information about the individuals concerned to match it against.
However, there are applications that require dates and times to be present to able to fulfill the objective. This is particularly true in therapeutic clinical trials in which the objective is to measure change in an outcome measure over time. Further, it is often necessary to correlate information from images with information from other sources, such as clinical and laboratory data, and dates and times need to be consistent.
Two mutually exclusive Options are specified to address these requirements:
-
Retain Longitudinal Temporal Information With Full Dates Option
-
Retain Longitudinal Temporal Information With Modified Dates Option
When the Retain Longitudinal Temporal Information With Full Dates Option is specified in addition to the Basic Application Level Confidentiality Profile, any dates and times present in the Attributes shall be retained, as described in Table E.1-1. The Attribute Longitudinal Temporal Information Modified (0028,0303) shall be added to the Dataset with a Value of "UNMODIFIED".
When the Retain Longitudinal Temporal Information With Modified Dates Option is specified in addition to the Basic Application Level Confidentiality Profile, any dates and times present in the Attributes listed in Table E.1-1 shall be modified. The modification of the dates and times shall be performed in a manner that:
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aggregates or transforms dates so as to reduce the possibility of matching for re-identification
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preserves the gross longitudinal temporal relationships between images obtained on different dates to the extent necessary for the application
-
preserves the fine temporal relationships between images and real-world events to the extent necessary for analysis of the images for the application
The Attribute Longitudinal Temporal Information Modified (0028,0303) shall be added to the Dataset with a Value of "MODIFIED".
Note
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Aggregation of dates may be performed by various means such as setting all dates to the first day of the month, all months to the first month of the year, etc., depending on the precision required for the application.
-
It is possible to modify all dates and times to dummy values by shifting them relative to an arbitrary event, and hence retain the precise longitudinal temporal relationships amongst a set of studies, when either de-identification of the entire set is performed at the same time, or some sort of mapping or database is kept to repeat this process on separate occasions. It may also be desirable to record the type of event and the temporal offset from that event, and Attributes are provided for that purpose; see Longitudinal Temporal Offset from Event (0012,0052) and Longitudinal Temporal Event Type (0012,0053) in the PS3.3 Section C.7.2.3 Clinical Trial Study Module.
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Transformation of dates and times should be considered together, in order to address studies that span midnight.
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Any transformation of times should be performed in such a manner as to not disrupt computations needed for analysis, such as comparison of start of injection time to the acquisition time for PET SUV, or extraction of time-intensity values from dynamic contrast enhanced studies.
The manner of date modification shall be described in the Conformance Statement.