DICOM PS3.3 2016c - Information Object Definitions

C.8.11.3 DX Image Module
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#### C.8.11.3 DX Image Module

Table C.8-70 contains IOD Attributes that describe a DX Image by specializing Attributes of the General Image Module and Image Pixel Module, and adding additional Attributes.

Table C.8-70. DX Image Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Image Type | (0008,0008) | 1 | Image identification characteristics. See Section C.8.11.3.1.1 for specialization.
Samples per Pixel | (0028,0002) | 1 | Number of samples in this image. Enumerated Values: 1
Photometric Interpretation | (0028,0004) | 1 | Specifies the intended interpretation of the pixel data. Enumerated Values: MONOCHROME1 MONOCHROME2
Bits Allocated | (0028,0100) | 1 | Number of bits allocated for each pixel sample. Enumerated Values: 8 16
Bits Stored | (0028,0101) | 1 | Number of bits stored for each pixel sample. Enumerated Values: 6 7 8 9 10 11 12 13 14 15 16
High Bit | (0028,0102) | 1 | Most significant bit for pixel sample data. Shall be one less than the value in Bit Stored (0028,0101).
Pixel Representation | (0028,0103) | 1 | Data representation of the pixel samples. Enumerated Values: 0000H Unsigned Integer
Pixel Intensity Relationship | (0028,1040) | 1 | The relationship between the Pixel sample values and the X-Ray beam intensity. Enumerated Values: LIN Linearly proportional to X-Ray beam intensity LOG Logarithmically proportional to X-Ray beam intensity See Section C.8.11.3.1.2 for further explanation.
Pixel Intensity Relationship Sign | (0028,1041) | 1 | The sign of the relationship between the Pixel sample values stored in Pixel Data (7FE0,0010) and the X-Ray beam intensity. Enumerated Values: +1 Lower pixel values correspond to less X-Ray beam intensity -1 Higher pixel values correspond to less X-Ray beam intensity See Section C.8.11.3.1.2 for further explanation.
Rescale Intercept | (0028,1052) | 1 | The value b in the relationship between stored values (SV) in Pixel Data (7FE0,0010) and the output units specified in Rescale Type (0028,1054). Output units = m*SV + b. Enumerated Values: 0 See Section C.8.11.3.1.2 for further explanation.
Rescale Slope | (0028,1053) | 1 | m in the equation specified by Rescale Intercept (0028,1052). Enumerated Values: 1 See Section C.8.11.3.1.2 for further explanation.
Rescale Type | (0028,1054) | 1 | Specifies the output units of Rescale Slope (0028,1053) and Rescale Intercept (0028,1052). Enumerated Values: US Unspecified See Section C.8.11.3.1.2 for further explanation.
Presentation LUT Shape | (2050,0020) | 1 | Specifies an identity transformation for the Presentation LUT, other than to account for the value of Photometric Interpretation (0028,0004), such that the output of all grayscale transformations defined in the IOD containing this Module are defined to be P-Values. Enumerated Values: IDENTITY output is in P-Values - shall be used if Photometric Interpretation (0028,0004) is MONOCHROME2. INVERSE output after inversion is in P-Values - shall be used if Photometric Interpretation (0028,0004) is MONOCHROME1. See Section C.8.11.3.1.2 for further explanation.
Lossy Image Compression | (0028,2110) | 1 | Specifies whether an Image has undergone lossy compression (at a point in its lifetime). Enumerated Values: 00 Image has NOT been subjected to lossy compression. 01 Image has been subjected to lossy compression. Once this value has been set to 01 it shall not be reset. See Section C.7.6.1.1.5.
Lossy Image Compression Ratio | (0028,2112) | 1C | Describes the approximate lossy compression ratio(s) that have been applied to this image. See Section C.7.6.1.1.5.2. Required if Lossy Image Compression (0028,2110) is "01".
Derivation Description | (0008,2111) | 3 | A text description of how this image was derived. See Section C.8.11.3.1.4 for further explanation.
Acquisition Device Processing Description | (0018,1400) | 3 | Indicates any visual processing performed on the images prior to exchange. See Section C.8.11.3.1.3 for further explanation.
Acquisition Device Processing Code | (0018,1401) | 3 | Code representing the device-specific processing associated with the image (e.g., Organ Filtering code) ### Note This Code is manufacturer specific but provides useful annotation information to the knowledgeable observer.
Patient Orientation | (0020,0020) | 1C | Patient direction of the rows and columns of the image. See Section C.7.6.1.1.1 for further explanation. Required if View Code Sequence (0054,0220) is not present or is present with an Item value other than (G-8300, SRT, "tissue specimen") or (G-8310, SRT, "tissue specimen from breast"). May be present otherwise.
Calibration Image | (0050,0004) | 3 | Indicates whether a reference object (phantom) of known size is present in the image and was used for calibration. Enumerated Values: YES NO Device is identified using the Device Module. See Section C.7.6.12 for further explanation.
Burned In Annotation | (0028,0301) | 1 | Indicates whether or not image contains sufficient burned in annotation to identify the patient and date the image was acquired. Enumerated Values: YES NO
VOI LUT Sequence | (0028,3010) | 1C | Defines a sequence of VOI LUTs. See Section C.8.11.3.1.5 for further explanation. One or more Items shall be included in this Sequence. Required if Presentation Intent Type (0008,0068) is FOR PRESENTATION and Window Center (0028,1050) is not present. May also be present if Window Center (0028,1050) is present.
>LUT Descriptor | (0028,3002) | 1 | Specifies the format of the LUT Data in this Sequence. See Section C.8.11.3.1.5 for further explanation.
>LUT Explanation | (0028,3003) | 3 | Free form text explanation of the meaning of the LUT.
>LUT Data | (0028,3006) | 1 | LUT Data in this Sequence.
Window Center | (0028,1050) | 1C | Defines a Window Center for display. See Section C.8.11.3.1.5 for further explanation. Required if Presentation Intent Type (0008,0068) is FOR PRESENTATION and VOI LUT Sequence (0028,3010) is not present. May also be present if VOI LUT Sequence (0028,3010) is present.
Window Width | (0028,1051) | 1C | Window Width for display. See Section C.8.11.3.1.5 for further explanation. Required if Window Center (0028,1050) is sent.
Window Center & Width Explanation | (0028,1055) | 3 | Free form explanation of the meaning of the Window Center and Width. Multiple values correspond to multiple Window Center and Width values.

##### C.8.11.3.1 DX Image Attribute Descriptions

###### C.8.11.3.1.1 Image Type

Value 1 shall identify the Pixel Data Characteristics in accordance with Section C.7.6.1.1.2 where the Enumerated Values are defined to be ORIGINAL or DERIVED.

### Note

DX images may still be of type ORIGINAL rather than DERIVED despite the possibility that they may have undergone some processing. In this case a DERIVED image would have undergone yet further processing to make it substantially different from the original.

Value 2 shall identify the Patient Examination Characteristics in accordance with Section C.7.6.1.1.2 where the Enumerated Values are defined to be PRIMARY or SECONDARY.

### Note

DX images generally use PRIMARY value for images captured from patient exposure.

If images from the same exposure exist with different Values of Image Type, then they shall have different SOP Instance UIDs.

### Note

Source Image Sequence (0008,2112) may be used to relate these images.

Value 3 (which is specific to the IOD) shall be present and have zero length (null value).

Other Values (4 and beyond) are optional and implementation specific.

###### C.8.11.3.1.2 Pixel Intensity Relationship and Grayscale Transformations

Pixel Intensity Relationship (0028,1040) and Pixel Intensity Relationship Sign (0028,1041) describe how the stored pixel values in Pixel Data (7FE0,0010) are related to the X-Ray beam intensity incident on the detector.

They do not define a transformation intended to be applied to the pixel data for presentation.

### Note

For example, if Pixel Intensity Relationship (0028,1040) is LIN and Pixel Intensity Relationship Sign (0028,1041) is -1, then lower values of Pixel Data (7FE0,0010) indicate higher X-Ray beam intensities corresponding to less radiographically dense regions projected on the image such as through air, and higher values of Pixel Data (7FE0,0010) indicate lower X-Ray beam intensities corresponding to more radiographically dense regions projected on the image such as through bone and radio-opaque contrast agents.

The transformation to be applied to the pixel data for presentation is defined by the successive application of the conceptual Modality LUT, the VOI Attributes and the conceptual Presentation LUT. This shall result in the output of P-Values.

Rescale Slope (0028,1053) and Rescale Intercept (0028,1052) define a linear subset of a conceptual Modality LUT transformation. For IODs that include this Module, these Attributes define an identity transformation. IODs that include the DX Image Module shall not include the Modality LUT Module.

The Presentation LUT Shape (2050,0020) defines a subset of a conceptual Presentation LUT. For IODs that include this Module, this Attribute defines an identity transformation or inverse identity transformation. IODs that include the DX Image Module shall not include the Presentation LUT Module.

Photometric Interpretation (0028,0004) indicates whether lower values that are the output of the VOI Attributes should be displayed as darker or lighter. Since the output of the equivalent of a conceptual Presentation LUT is in P-Values, which are defined in PS3.14 such that lower values correspond to lower luminance levels, then the definition of the Presentation LUT Shape (2050,0020), otherwise intended to be an identity transformation, must take into account the effect of the value specified for Photometric Interpretation (0028,0004).

### Note

Regardless of the values of Pixel Intensity Relationship (0028,1040) and Pixel Intensity Relationship Sign (0028,1041), the grayscale transformations to be applied to Pixel Data (7FE0,0010) are defined by the equivalent of the Modality LUT (Rescale Slope (0028,1053) and Rescale Intercept (0028,1052)), Value of Interest Attributes, Photometric Interpretation (0028,0004) and the equivalent of the Presentation LUT (Presentation LUT Shape (2050,0020)). However, the combination of the grayscale transformations and the description of the pixel intensity relationship, together define whether, for example, air is expected to be displayed as black or white.

###### C.8.11.3.1.3 Acquisition Device Processing Description

Acquisition Device Processing Description (0018,1400) provides some indication in human readable text of the digital processing on the images before exchange. Examples of this processing are: edge enhanced, subtracted, time filtered, gamma corrected, convolved (spatially filtered).

###### C.8.11.3.1.4 Derivation Description

If an Image is identified to be a Derived image in Image Type (0008,0008), Derivation Description (0008,2111) is an optional and implementation specific text description of the way the image was derived from an original image. As applied to DX images, it may be used to describe derivation operations such as edge enhancement, temporal filtering, digital subtraction, or other linear and non-linear transformations.

###### C.8.11.3.1.5 VOI Attributes

The Attributes of the VOI LUT Module are specialized in the DX Image Module.

Window Center (0028,1050) and Window Width (0028,1051) specify a linear conversion (unless otherwise specified by the value of VOI LUT Function (0028,1056); See Section C.11.2.1.3) from the output of the (conceptual) Modality LUT values to the input to the (conceptual) Presentation LUT. Window Center contains the value that is the center of the window. Window Width contains the width of the window.

The application of Window Center (0028,1050) and Window Width (0028,1051) shall not produce a signed result.

### Note

If the Presentation LUT Shape (2050,0020) is IDENTITY, then the result of applying Window Center (0028,1050) and Window Width (0028,1051) is P-Values.

If multiple values are present, both Attributes shall have the same number of values and shall be considered as pairs. Multiple values indicate that multiple alternative views should be presented.

The VOI LUT Sequence specifies a (potentially non-linear) conversion from the output of the (conceptual) Modality LUT values to the input to the (conceptual) Presentation LUT.

If multiple items are present in VOI LUT Sequence (0028,3010), only one shall be applied. Multiple items indicate that multiple alternative views should be presented.

If any VOI LUT Attributes are included by an Image, a Window Width and Window Center or the VOI LUT Table, but not both,shall be applied to the Image for display. Inclusion of both indicates that multiple alternative views should be presented.

The three values of LUT Descriptor (0028,3002) describe the format of LUT Data (0028,3006).

The first value is the number of entries in the lookup table.

The second value is the first stored pixel value mapped. This pixel value is mapped to the first entry in the LUT. All image pixel values less than the first value mapped are also mapped to the first entry in the LUT Data. An image pixel value one greater than the first value mapped is mapped to the second entry in the LUT Data. Subsequent image pixel values are mapped to the subsequent entries in the LUT Data up to an image pixel value equal to number of entries + first value mapped - 1 that is mapped to the last entry in the LUT Data. Image pixel values greater than number of entries + first value mapped are also mapped to the last entry in the LUT Data.

The third value specifies the number of bits for each entry in the LUT Data (analogous to "bits stored"). It shall be between 10-16. The LUT Data shall be stored in a format equivalent to 16 "bits allocated" and "high bit" equal to "bits stored" - 1. The third value conveys the range of LUT entry values. These unsigned LUT entry values shall range between 0 and 2n-1, where n is the third value of the LUT Descriptor.

### Note

1. The third value is restricted in the VOI LUT Module to 8 or 16 but is specialized here.

2. The first and second values are not specialized and are the same as in the VOI LUT Module.

LUT Data (0028,3006) contains the LUT entry values.

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DICOM PS3.3 2016c - Information Object Definitions