[Dcmlib] [Fwd: Re: Unique tag within a dicom file]

[Mathieu Malaterre]

-------- Original Message --------
Subject: Re: Unique tag within a dicom file
Date: Tue, 16 Nov 2004 14:57:33 -0500
From: Andrei Leontiev <aleontievt at hotmail.com>
Newsgroups: comp.protocols.dicom
References: <wp9kd.375974$bp1.366155 at twister.nyroc.rr.com>

Hi, Mathieu -

No, there is no "general" key to identify a particular DICOM attribute
within DICOM Data Set (both DICOM messages and DICOM files contain Data Sets
augmented by some additional information).

On the top level of Data Set you can only "uniquely identify an attribute
which may or may not be a sequence. In the latter case, the value of the
attribute is in fact one or more Data Sets, and you have to parse them
exactly the same way you did the Top level Data Set. And these Data Sets can
in turn contain sequences containing Data Sets ad infinitum. DICOM SR
objects are especially notorious about it.

In other words, you should not consider the structure of DICOM Data Set as
flat where every element can be accessed directly, via offset, "unique key"
or any other mechanism, but rather as a tree where you have to navigate from
one node to another until you reach the leaf node. So, it is not enough to
know the tag of particular element, but also tags of all sequences it is
included into, i.e., path from the root to the leaf node.

Andrei

On 11/9/04 3:04 PM, in article wp9kd.375974$bp1.366155 at twister.nyroc.rr.com,
"Mathieu Malaterre" <mmalaterNOSP at Mnycap.rr.com> wrote:

> Hello,
> 
> I am a bit confused. I thought that a group + element, would give me a
> unique key to a Tag. But this isn't true within a sequence. Is there a
> 'general' key to identify a dicom value, within or not a sequence.
> 
> Thanks
> Mathieu
>