Hello all,

we received DICOM data from a country using Traditional Chinese. Much to our surprise, the data is encoded with (0008,0005) SpecificCharacterSet "ISO_IR 100". Our application reads the strings according to the standard and produces unreadable stuff, while other applications recognize the Chinese characters.
Next surprise: When dcmdump-ing the file, notepad++ also recognizes the Chinese characters correctly, so I can add a few lines of the dump. This is obviously a two-byte encoding, but I could not find any reference. What is the magic here?
Thank you, Sebastian

# Dicom-File-Format

# Dicom-Meta-Information-Header
# Used TransferSyntax: Little Endian Explicit
(0002,0000) UL 198 # 4, 1 FileMetaInformationGroupLength
(0002,0001) OB 00\01 # 2, 1 FileMetaInformationVersion
(0002,0002) UI =CTImageStorage # 26, 1 MediaStorageSOPClassUID
(0002,0003) UI [1.2.840.113619.2......................] # 56, 1 MediaStorageSOPInstanceUID
(0002,0010) UI =LittleEndianImplicit # 18, 1 TransferSyntaxUID
(0002,0012) UI [1.2.410.200010.99.3.5] # 22, 1 ImplementationClassUID
(0002,0013) SH [INF_4.5] # 8, 1 ImplementationVersionName

# Dicom-Data-Set
# Used TransferSyntax: Little Endian Implicit
(0008,0005) CS [ISO_IR 100] # 10, 1 SpecificCharacterSet
(0008,0016) UI =CTImageStorage # 26, 1 SOPClassUID
(0008,0018) UI [1.2.840.113619.2......................] # 56, 1 SOPInstanceUID
(0008,0060) CS [CT] # 2, 1 Modality
(0008,0070) LO [GE MEDICAL SYSTEMS] # 18, 1 Manufacturer
(0008,0080) LO [....綜合醫院] # 14, 1 InstitutionName
(0008,1030) LO [Low Dose Lung CT 低劑量肺部檢查(......補助)] # 44, 1 StudyDescription
(0008,1090) LO [Optima CT660] # 12, 1 ManufacturerModelName

Are you sure that these Chinese characters aren't just encoded in utf-8 in the DICOM file?

If they are, then notepad++ will probably be able to autodetect that they are utf-8 and display them properly, while applications that strictly enforce "ISO_IR 100" will display garbage.

If you can post a hex dump of one of the data elements that contains the characters, I could inspect it to see what encoding is used.

Hi David,
here is a dump of two of the affected tags, created with dcmdump:
>dcmdump +Qn +L +P InstitutionName +P StudyDescription "chinese_org.dcm"
(0008,0080) LO [©É¤¯ºî¦XÂå°|] # 14, 1 InstitutionName
(0008,1030) LO [Low Dose Lung CT §C¾¯¶qªÍ³¡Àˬd(®ç¶é¥«¸É§U)] # 44, 1 StudyDescription

Thanks for your help!

David Gobbi schrieb am Freitag, 28. April 2023 um 18:50:53 UTC+2:
> Are you sure that these Chinese characters aren't just encoded in utf-8 in the DICOM file?
>
> If they are, then notepad++ will probably be able to autodetect that they are utf-8 and display them properly, while applications that strictly enforce "ISO_IR 100" will display garbage.
>
> If you can post a hex dump of one of the data elements that contains the characters, I could inspect it to see what encoding is used.

The encoding is Big5. I'm suprised that Notepad++ could autodetect it. Here is how I checked the encoding in Python:

b = bytearray([169,201,164,175,186,238,166,194,229,176])
print(b.decode('big5'))
怡仁綜汕撠

I tried UTF-8 first, then Big5, and voila, that's what it was.

Although Big5 isn't part of the DICOM standard, I have a tool that can dump these files:
https://github.com/dgobbi/vtk-dicom/wiki/dicomdump
https://github.com/dgobbi/vtk-dicom/releases/tag/v0.8.14

dicomdump --charset big5 chinese_org.dcm

On Friday, 28 April 2023 at 11:46:49 UTC-6, David Gobbi wrote:

> dicomdump --charset big5 chinese_org.dcm

Ah, I forgot that for this to work, the original CharacterSet has to be removed first, e.g.

dcmodify -e 0008,0005 chinese_org.dcm

Thank you so much!

I was surprised by this capability of notepad++ as well. Then I learned that the primary author has Taiwanese roots: https://donho.github.io/

David Gobbi schrieb am Freitag, 28. April 2023 um 19:53:58 UTC+2:
> On Friday, 28 April 2023 at 11:46:49 UTC-6, David Gobbi wrote:
>
> > dicomdump --charset big5 chinese_org.dcm
>
> Ah, I forgot that for this to work, the original CharacterSet has to be removed first, e.g.
>
> dcmodify -e 0008,0005 chinese_org.dcm