changing dicom-dict.txt has no effect

Hi,

I have MR images with a large amount of dicom private tags. I have copied and edited the dicom-dict.txt file to include as the final line

(2005,10A9) UT DistortionCorrection 1

and saved this as dicom-dict-copy.txt, which I had to manually import into the toolbox folder given the permissions on my pc.

I set dicom-dict-copy.txt as the new dictionary using dicomdict('set',filepath)

this is confirmed with dicomdict('get') = 'C:\Program Files\MATLAB\R2021b\toolbox\images\iptformats\dicom-dict-copy.txt'

However, the tag I have set is not recognised when i call inf.DistortionCorrection (inf = dicominfo(image)). Does anyone know why this does not work?

Answer 1

[Simon Chan]

You may refer to the following and try to create a new DICOM tag and write it to a new DICOM image.

After that, the DICOM header in the new image should contains your required information.

filename = 'Original.dcm';
I = dicomread(filename);
header = dicominfo(filename);
header.(dicomlookup('2005', '10A9'))='1';
newname = 'New.dcm';
dicomwrite(I,newname,header,'CreateMode','copy','WritePrivate',true);
new_header = dicominfo(newname);

[Cameron Starling]

Hi Simon, thanks for your help. Unfortunately I don't want to create any more headers, but I do need to be able to update the dicom tag lookup document. At present I am unable to access the private tags, which matlab just reads as a size of variable whilst undeclared. The problem is, despite declaring this variable, it is still unrecognised.

[Simon Chan]

The private tag will be something like this from the DICOM header:

Private_01f1_1026: [6×1 uint8]
Private_01f1_1027: [2×1 uint8]
Private_01f1_1032: [14×1 uint8]

You can access via

header.Private_01f1_1032

Take the transpose of the header in a character array:

char(header.Private_01f1_1032')

give the following result:

'VIEW_FROM_FEET'

So if you know the content is a number, you may use function str2double to convert it.

[Cameron Starling]

Brilliant, thanks very much. I am now able to access the information I'm after. I will need to revisit the topic of editing the dicom dictionary though. I'm sure this will be handy in the future.

[Simon Chan]

Great! Please accept the answer if you feel it useful.