Is this Meta Information?

[bsapach]

Hello,

I've been trying to get DCM_DiffusionGradientDirection out of a dicom file, with no success. (Tag Not Found). But when I open the file in a text editor I see:


DiffusionGradientDirection □□□□□□□FD□□□□□M□□□□□M□□□□□□0.00000□□□□□□M□□□□□-0.7072000□□□□□M□□□□□□0.7071000


What is this? Is this meta-information? Or some proprietary data? This element is indeed FD, and those appear to be sine values, how can I access this information?

[Michael Onken]

Hi,

perhaps it would be easier not to read the binary DICOM file using a text editor, but e. g. dcmdump, that's within the DCMTK release. In the output, you probably will find the tag you're searching again.

Regards,
Michael

[Alexander Fedotov]

[quote="bsapach"]Hello,

I've been trying to get DCM_DiffusionGradientDirection out of a dicom file, with no success. (Tag Not Found). But when I open the file in a text editor I see:
[/quote]

A binary file (DICOM) is better to open by a binary (HEX) editor.

And this attribute (0018,9076) is the sequence,
are you sure that the correct method of DcmItem has been called?

Alexander.

[bsapach]

perhaps it would be easier not to read the binary DICOM file using a text editor, but e. g. dcmdump, that's within the DCMTK release. In the output, you probably will find the tag you're searching again.

DcmDump gives me this on any of these files does not give me any "diffusion" values at all, in fact the word diffusion doesn't occur in the output at all. There are these however:


(0029,0010) LO [SIEMENS CSA HEADER] # 18, 1 PrivateCreator
(0029,0011) LO [SIEMENS MEDCOM HEADER] # 22, 1 PrivateCreator
(0029,0012) LO [SIEMENS MEDCOM HEADER2] # 22, 1 PrivateCreator
(0029,1008) CS [IMAGE NUM 4] # 12, 1 Unknown Tag & Data
(0029,1009) LO [20051027] # 8, 1 Unknown Tag & Data
(0029,1010) OB 53\56\31\30\04\03\02\01\38\00\00\00\4d\00\00\00\45\63\68\6f\4c\69... # 6936, 1 Unknown Tag & Data
(0029,1018) CS [MR] # 2, 1 Unknown Tag & Data
(0029,1019) LO [20051027] # 8, 1 Unknown Tag & Data
(0029,1020) OB 53\56\31\30\04\03\02\01\2c\00\00\00\4d\00\00\00\55\73\65\64\50\61... # 37944, 1 Unknown Tag & Data
(0029,1131) LO [4.0.72431994] # 12, 1 Unknown Tag & Data
(0029,1132) UL 131072 # 4, 1 Unknown Tag & Data
(0029,1133) UL 0 # 4, 1 Unknown Tag & Data
(0029,1134) CS [DB TO DICOM] # 12, 1 Unknown Tag & Data
(0029,1260) LO [com] # 4, 1 Unknown Tag & Data


So I suspect that all of this information is in one of these Unknown elements.

When I look at the file in a text editor I can find "DiffusionGradientDirection" and the values I mentioned previously. But "Diffusion..." shouldn't be present (as text) in a normal binary DICOM element should it? And the fact that the values are visible in the text editor means they were written as ascii text, not binary floats. This data is from a Siemens Sonata scanner, and it looks like there is a great deal more ascii data in the file.

Lastly, when I try using DicomDataset::findAndGetSequence() and DicomDataset::findAndGetSequenceItem() on DCM_DiffusionGradientDirectionSequence I get "Tag Not Found". As far as I know these are the only functions for retreiving an SQ item.

Beau

[Michael Onken]

right.

Perhaps the text is hidden in one of the private attribute values. You could try a

Code: Select all

dcmdump YOUR_FILE +L > dump.txt

This will dump all tag values, including very long values like pixel data etc. and redirects all output to the file dump.txt.
Then open dump.txt in your favourite text editor and search a string, you're interested in. You should find the desired string there, otherwise it could be an error in the file itself.

A last possibility could be, that the text is hidden in the abitrary 128 Byte Preambel, that precedes any DICOM file. But that would be a very strange way to store such a value...

Regards and good luck,
Michael