loading just the meta header information

[xargon]

Hi everyone,

I am using the DCMTK library on Linux and have a need where I have to recursively scan and build volumes from files in a user specified directory. The problem is that I am running out of memory doing these scans.

To arrange the DICOM files, I only need the information from the headers.

I am loading the files as follows:

I have a DCMFileFormat object that it a class member:

Code: Select all

DcmFileFormat *         m_dcmFileFormat; 

To load the file, I am using:

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m_dcmFileFormat->loadFile(fileName, EXS_Unknown, EGL_noChange, DCM_MaxReadLength, ERM_fileOnly)

My question is does the loadFile statement load the whole file (with data) into the memory? If yes, is there a way to delay the loading unless the call is made to retrieve DCM_PixelData?

Cheers,
Luca

[Michael Onken]

Hi Luca,

m_dcmFileFormat->loadFile(fileName, EXS_Unknown, EGL_noChange, DCM_MaxReadLength, ERM_fileOnly)

Your call loads all elements into memory that are larger than the size (in bytes) given by DCM_MaxReadLength. Usually this value is set to 4 KB so only elements (including pixel data element) are loaded having a value length of more than 4096 bytes. If you want to load bigger values per default, you can increment this threshold. For your purposes this should be a good default.

The last parameter in the loadFile() call denotes, whether DCMTK should try to parse a DICOM file that includes a meta header (which is the usual case) or a file without metaheader (which is what you choosed with ERM_fileOnly). Best choice for this option should be the value ERM_autoDetect to let DCMTK decide what to do. Only if you already know that your files do not contain metaheader information you should use ERM_fileOnly.

Regards,
Michael

[xargon]

Hi Michael,

Thanks for the reply. You mention:

your call loads all elements into memory that are larger than the size (in bytes) given by DCM_MaxReadLength.

Don't you mean that all elements less than the size given by DCM_MaxReadLength are loaded?

Thanks,
Luca

[Jörg Riesmeier]

Don't you mean that all elements less than the size given by DCM_MaxReadLength are loaded?

Yes, you are correct.

Another little mistake in Michael's posting: ERM_fileOnly does mean exactly the opposite, i.e. only DICOM files with meta header are loaded

[Michael Onken]

Hoppla..., of course it is correct, what Jörg points out...I'm so sorry
Michael