Date shift

Shift every date by a fixed offset, preserving intervals and times.

Date shifting moves every date in a study by the same number of days. The dates no longer match the real ones, but the time between two scans and the time of day stay as they were. PS3.15 calls this the “Retain Longitudinal Temporal Information with Modified Dates” option.

What changes

• The offset is added to every DA value and to the date part of every DT value, including values inside sequences. Times stay as they are.
• Dates the profile would otherwise remove, such as Date of Last Calibration, are kept and shifted, because the option keeps them.
• Patient Birth Date is blanked, not shifted. Patient’s Age, sex, size and weight are kept instead, so the age at each scan stays in the file. PS3.15 calls this the “Retain Patient Characteristics” option. HIPAA and Teaching keep only age, capped at 89, and sex.
• With private tags removed, the Basic, +Pixel and HIPAA profiles record both options in De-identification Method Code Sequence (0012,0064) as codes 113107 and 113108, after 113100 for the Basic Profile.

Tip Auto derives an offset from the Patient ID, keyed by a secret stored on this installation. The same patient gets the same offset as long as you use the same browser or Mac app and click Auto before the Patient ID is replaced.

dcmage does not save the offset. Record it in your study records if you may need to reverse the shift.

For the full list of what gets shifted, the limits, and how to check the result, see DICOM date shifting.