Modality LUT Sequence

[paolom]

Hi,
I'm creating a DicomImage with default constructor and I obtain a white image.
After a dump, I found that this DICOM file has this field:

Code: Select all

(0028,3000) SQ (Sequence with explicit length #=1)      # 5820, 1 ModalityLUTSequence
  (fffe,e000) na (Item with explicit length #=4)          # 5812, 1 Item
    (0028,3002) SS 2881\-240\16                             #   6, 3 LUTDescriptor
    (0028,3003) LO [CRTLUT]                                 #   6, 1 LUTExplanation
    (0028,3004) LO [OD]                                     #   2, 1 ModalityLUTType
    (0028,3006) OW 0000\0000\0001\0001\0001\0002\0002\0002\0003\0003\0004\0004\0004... # 5762, 1 LUTData
  (fffe,e00d) na (ItemDelimitationItem for re-encoding)   #   0, 0 ItemDelimitationItem
(fffe,e0dd) na (SequenceDelimitationItem for re-encod.) #   0, 0 SequenceDelimitationItem

If I create a DicomImage with the CIF_IgnoreModalityTransformation option on the constructor, I can see the right image (as reported on the documentation, ignore modality transformation).

My questions are:
1) Why if I use the default constructor (whit modality transformation) I see I white image? Is it an error of the DICOM file's data?
2) Is it possible to change the use of the modality transformation by a function and not in the constructor?
3) How can I determine if the application of the modality LUT give to me a right image?

Thanks

[J. Riesmeier]

Re. 1) I guess that the reason for the "white image" is an inappropriate Modality LUT stored in the DICOM object.
Re. 2) No, there is no way to do it after the constructor has been called. This is because the intermediate representation of the pixel data is created during construction.
Re. 3) You could check whether the content of the LUT (including the descriptor) is appropriate for the pixel data, i.e. whether the output of the LUT creates many different grayscale values.

[paolom]

..whether the output of the LUT creates many different grayscale values

So do you think that I need to create the DicomImage whit the default modality LUT and analyze the pixelData, pixel by pixel, and If all the pixels are white recreate the DicomImage with the CIF_IgnoreModalityTransformation ?
Is there another way?!

[J. Riesmeier]

No, if you are in doubt that the result might not be OK you could check the LUT Data and Descriptor for abnormalities, i.e. before you start the DicomImage processing.