[Insight-users] Possible bug reading DICOM MONOCHROME1 images with Pixel Padding Value != 2^bits stored-1

[Iván Macía]

Hi,

 

I tried to load a DICOM MONOCHROME1 image (MG) and resulting output values
are outside the range specified in the DICOM fields. The resulting image is
shown in black with the W/L settings taken from DICOM.

 

Debugging a bit and getting deep into ITK, it seems like the problem lies in
the GDCM library in gdcm::PixelReadConvert::ConvertFixGreyLevels() and the
interpretation of (0028,0120) Pixel Padding Value and (0028,0107) Largest
Image Pixel Value. For this image, the Largest Image Pixel Value is 32767
and the Pixel Padding Value 32767 (recommended to be 2^16-1 = 65535) but not
mandatory.

 

In gdcm::PixelReadConvert::ConvertFixGreyLevels() always pixels are
converted in the form:

 

value = 65535 - value

 

which results in pixels above the 5571 - 32767 range for this image.

 

In my opinion, in this case it should be 

 

value = 32767 - value

 

which gives the correct values.

 

I am not totally sure, but the image seems to be following the standard.
Could please someone confirm this?

We have several of these images and none is loading correctly

 

I added a new bug entry in Mantis for this

http://public.kitware.com/Bug/view.php?id=8538

 

Thanks in advance 

 

Iván

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