Working with DICOM LUT

Modality LUT

A Modality LUT allows the transformation of manufacturer-dependent pixel values into manufacturer-independent pixel values (e.g., Hounsfield units for CT images). The "Modality LUT" may be contained within an image, a Presentation State (that references an image), or as a "Standalone Modality LUT" (that references an image). The "Rescale Slope" (0028,1053) and "Rescale Intercept" (0028,1052) elements are used to describe the transformation when it is linear, while the "Modality LUT Sequence" (0028,3000) element is used to describe non-linear transformations. In both cases it is implied that the transformation can only occur for grayscale data, that is, images with "Photometric Interpretation" values of "MONOCHROME1" or "MONOCHROME2".

Methods and Properties

Member Description
DicomDataSet.DeleteModalityLut Used to remove the Modality LUT from a DICOM Data Set.
DicomDataSet.GetModalityLutAttributes and
DicomDataSet.SetModalityLut
Used to retrieve and update the values of the elements that describe a "Modality LUT" respectively.
DicomDataSet.GetModalityLutData Used to get the "LUT Data" (0028,3006) under the Modality LUT Sequence (0028,3000).
DicomModalityLutAttributes.IsModalityLutSequence If set to true and the transformation is non-linear, then DicomModalityLutAttributes.NumberOfEntries , DicomModalityLutAttributes.FirstStoredPixelValueMapped , and DicomModalityLutAttributes.EntryBits hold the values of the "LUT Descriptor" (0028,3002).
DicomModalityLutAttributes The properties describe all the attributes related to a "Modality LUT ". If the transformation defined by the LUT is linear, then DicomModalityLutAttributes.IsRescaleSlopeIntercept is set to true, then DicomModalityLutAttributes.RescaleIntercept and DicomModalityLutAttributes.RescaleSlope hold the values for "Rescale Intercept" (0028,1052) and "Rescale Slope" (0028,1053), respectively.

VOI LUT

A VOI LUT allows the transformation of the modality pixel values into pixel values that are meaningful for print or display. This transformation is applied after any "Modality LUT". The "VOI LUT" may be contained within an image, or a Presentation State (that references an image), or as a "Standalone VOI LUT" (that references an image). "Window Center" (0028,1050) and "Window Width" (0028,1051) are used to describe the transformation when it's linear, while the "VOI LUT Sequence" (0028,3010) is used to describe non-linear transformations. In both cases it is implied that the transformation can only occur for grayscale data (images with "Photometric Interpretation" values of "MONOCHROME1" and "MONOCHROME2"). If multiple values are present for the "Window Center" and "Window Width", both attributes shall have the same number of values and shall be considered as pairs. Multiple values indicate that multiple alternative views may be presented. If multiple items are present in "VOI LUT Sequence" (0028,3010), only one may be applied to the image for display. Multiple items indicate that multiple alternative views may be presented.

Methods and Properties

Member Description
DicomDataSet.DeleteVoiLut Used to delete all the elements related to a non-linear VOI LUT call.
DicomDataSet.DeleteWindow Used to delete all the elements related to a linear VOI LUT call.
DicomDataSet.GetVoiLut Used when the VOI LUT is non-linear, to get the format of the "LUT Data" under the "VOI LUT Sequence".
DicomDataSet.GetVoiLutData Used to get the table data ("LUT Data") itself.
DicomDataSet.GetWindow and
DicomDataSet.SetWindow
Use to retrieve and update the attributes that describe "Window Center" and "Window Width".
DicomDataSet.GetWindowCount Used to obtain the number of values under the window center element.
DicomDataSet.SetVoiLut Used to set the "LUT Data", for both the format of the data and the data itself.
DicomDataSet.VoiLutCount Used to obtain the number of items under the VOI LUT Sequence (0028,3010).

Palette Color Lookup Table

A Palette Color Lookup Table is used inside 8- and 16-bit color images where the pixel value is used as an index into each of the Red, Blue, and Green Palette Color Lookup Tables (0028,1101-1103&1201-1203). The DICOM standard defines two types of tables: "Contiguous Palette Color Tables" where the data for each table is represented by a single contiguous stream and "Segmented Palette Color Tables" where the data is stored in each table as a series of segments. Both types are supported by LEADTOOLS.

Methods and Properties

Member Description
DicomDataSet.DeletePaletteColorLut Used to remove the Palette Color Lookup Table from a DICOM Data Set.
DicomDataSet.GetPaletteColorLutAttributes and
DicomDataSet.SetPaletteColorLutAttributes
Used to retrieve or set the attributes that describe a Palette Color Lookup Table .
DicomDataSet.GetPaletteColorLutData and
DicomDataSet.SetPaletteColorLutData
Used to retrieve or set the table entries under "Red", " Green" or "Blue".

See Also

DicomDataSet

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