with regard to DICOM you probably refer to Supplement 55 "Attribute
Level Confidentiality (including De-identification)" which has also
been incorporated into DICOM 2003 (part 15, annex E).
And you're right, there have been a couple of discussions in this
group about anonymization in the past. Search for "anonymization",
"anonymize", "hipaa" or "supplement 55" in Google Groups.
Here's one of these discussions (I hope this link really works):
http://groups.google.com/groups?th=2e654e8fc982b408
Regards,
Joerg Riesmeier