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

[Bill Lorensen]

Mathieu,

Can it be fixed in gdcm 1.x?

Bill

On Mon, Feb 16, 2009 at 10:48 AM, Mathieu Malaterre
<mathieu.malaterre at gmail.com> wrote:
> On Mon, Feb 16, 2009 at 1:03 PM, Iván Macía <imacia at vicomtech.org> wrote:
>> 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
>
> Agreed with diagnosis. Thanks for bug report.
>
> If you switch to gdcm 2.x (using ITK_USE_SYSTEM_GDCM) this bug will go away.
>
> Thanks,
> --
> Mathieu
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