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Forum: Medical Applications
Re: Question Bug in DICOM example / "ReadPatientDataFile" ? (Holger Gottschlag)
Date: 03 Aug, 2011
From: Asja Pfaffenberger <Asja Pfaffenberger>

Hi Holger,

I agree with you. My way of avoiding the "10" was to modify DicomHandler::GetMaterialIndex where the conversion from density to material index takes place, since i wanted to be notified if the density exceeds the range for which materials are given. (But the effect is the same.) I would say, setting the index to "9" is fine as long as there are really no other materials in the dicom data set used with the example, like hip implants etc. Otherwise a new material and interval have to be defined.

Other modifications i made are specific to the dicom files i am reading in, but i will report them here since similar problems may be encountered by others. They refer to v9.4.p02.

1) Tag 0x00201041 "Slice Location" is type 3, i.e. optional (cf. ftp://medical.nema.org/medical/dicom/2009/), and was not used in the dicom data set i had, so i had the problem of not having continuous slice numbering since "Slice Location" was 0 for every slice. I then decided to use the z coordinate in 0x00200032 "Image Position" instead which is type 2 and should be present in all dicom data sets. This works fine.

2) Reading of the actual image started 8 bytes too early. I realised that by having unrealistically high Hounsfield units and DicomHandler::Pixel2Desinty therefore issued "@@@ Error density = -1 ...". You find attached a screen shot of the contents of our file, where the tag for the start of the pixels is 0x7fe 0010. (This info is for the authors of the example.) I do not quote our bug fix here since it is neither general nor nice.

With these modifications, the example seems to work.

Best regards, Asja

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