C.8.7 X-Ray Modules
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### C.8.7 X-Ray Modules

This Section describes Modules used in one or more X-Ray IODs. These Modules contain Attributes that are specific to X-Ray images.

#### C.8.7.1 X-Ray Image Module

Table C.8-26. X-Ray Image Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Frame Increment Pointer | (0028,0009) | 1C | Required if Multi-frame Image. Contains the Data Element Tag of the attribute that is used as the Frame increment in Multi-frame image pixel data (see Section C.7.6.6). Enumerated Values: 00181063H Frame Time (0018,1063) 00181065H Frame Time Vector (0018,1065)
Lossy Image Compression | (0028,2110) | 1C | 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 Required if Lossy Compression has been performed on the Image. May be present otherwise.
Image Type | (0008,0008) | 1 | Image identification characteristics. See Section C.8.7.1.1.1 for specialization.
Pixel Intensity Relationship | (0028,1040) | 1 | The relationship between the Pixel sample values and the X-Ray beam intensity. See Section C.8.7.1.1.2.
Samples per Pixel | (0028,0002) | 1 | Number of samples (color planes) in this image shall have a value of 1.
Photometric Interpretation | (0028,0004) | 1 | Specifies the intended interpretation of the pixel data. Only MONOCHROME2 may be used.
Bits Allocated | (0028,0100) | 1 | Number of bits allocated for each pixel sample. See Section C.8.7.1.1.6.
Bits Stored | (0028,0101) | 1 | Number of bits stored for each pixel sample. See Section C.8.7.1.1.7.
High Bit | (0028,0102) | 1 | Most significant bit for pixel sample data. See Section C.8.7.1.1.8.
Pixel Representation | (0028,0103) | 1 | Data representation of the pixel samples. Shall have the value: 0000H = Unsigned Integer.
Scan Options | (0018,0022) | 3 | Parameters of scanning sequence. See Section C.8.7.1.1.4.
Include Table 10-7 “General Anatomy Optional Macro Attributes” | No Context ID for the Anatomic Region Sequence is defined.
R Wave Pointer | (0028,6040) | 3 | Marks the location(s) of the R Wave in the cardiac cycles by referencing frame numbers; frame numbers begin with 1.
Referenced Image Sequence | (0008,1140) | 1C | Other images significantly related to this image. Shall be present if Image Type (0008,0008) Value 3 is BIPLANE A or BIPLANE B. May be present otherwise. One or more Items shall be included in this Sequence. See Section C.8.7.1.1.13.
>Include Table 10-3 “Image SOP Instance Reference Macro Attributes” |
>Purpose of Reference Code Sequence | (0040,A170) | 3 | Describes the purpose for which the reference is made. Only a single Item is permitted in this Sequence.
>>Include Table 8.8-1 “Code Sequence Macro Attributes” | Defined CID 7201 “Referenced Image Purposes of Reference”.
Derivation Description | (0008,2111) | 3 | A text description of how this image was derived. See Section C.8.7.1.1.5 for further explanation.
Acquisition Device Processing Description | (0018,1400) | 3 | Indicates any visual processing performed on the images prior to exchange. See Section C.8.7.1.1.3.
Frame Label Vector | (0018,2002) | 3 | A multi-valued attribute that contains a descriptive label for each of the image frames. The number of values shall equal the number of frames.
Frame Dimension Pointer | (0028,000A) | 3 | Contains the Data Element Tags of one or more attributes that vary or increment for the frames of a multi-frame image. See Section C.8.7.1.1.12. Shall not be present if it would contain only one value and that value would be Frame Time (0018,1063) or Frame Time Vector (0018,1065).
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.

##### C.8.7.1.1 X-Ray Image Attribute Descriptions

###### C.8.7.1.1.1 Image Type

The Image Type attribute identifies important image characteristics in a multiple valued data element. For X-Ray, Image Type is specialized as follows:

- Value 1 shall identify the Pixel Data Characteristics in accordance with Section C.7.6.1.1.2

  Enumerated Values:

  ORIGINAL

  DERIVED

  ### Note

  X-Ray images generally use PRIMARY value for images captured from patient exposure.

- Value 2 shall identify the Patient Examination Characteristics in accordance with Section C.7.6.1.1.2

  Enumerated Values:

  PRIMARY

  SECONDARY

- Value 3 shall identify the image set in terms of the imaging planes.

  Enumerated Values:

  SINGLE PLANE

    Image is a single plane acquisition

  BIPLANE A

    Image is the first plane (e.g., Frontal) of a Bi-plane acquisition

  BIPLANE B

    Image is the second plane (e.g., Lateral) of a Bi-plane acquisition

- Other Values are implementation specific (optional).

###### C.8.7.1.1.2 Pixel Intensity Relationship

Pixel Intensity Relationship (0028,1040) shall identify the relationship of the pixel values to the X-Ray beam intensity.

Defined Terms:

LIN

  Approximately proportional to X-Ray beam intensity;

LOG

  Non-linear "Log Function"; A Modality LUT shall be included with the image to allow it to be scaled back to its proportional value to X-Ray beam intensity;

DISP

  Ready to be displayed; A Modality LUT may be included with the image to allow it to be scaled back to its proportional value to X-Ray beam intensity. The Attribute Acquisition Device Processing Description may be used to provide some indication on the pre-processing performed to create the ready to be displayed image.

###### C.8.7.1.1.3 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.8.7.1.1.4 Scan Options

The Scan Options attribute identifies any acquisition technique that was used during the acquisition of the image.

Defined Terms:

EKG

  EKG Event Trigger

PHY

  Physiological Event Trigger

TOMO

  Tomography

CHASE

  Bolus Chasing

ROTA

  Rotation

###### C.8.7.1.1.5 Derivation Description

If an Image is identified to be a Derived image (see Section C.8.7.1.1.1), 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 X-Ray 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.8.7.1.1.6 Bits Allocated

Enumerated Values:

8

16

###### C.8.7.1.1.7 Bits Stored

Enumerated Values:

8

10

12

16

###### C.8.7.1.1.8 High Bit

For X-Ray Images, High Bit (0028,0102) shall be one less than the value in Bit Stored.

###### C.8.7.1.1.9 Synchronization of Frame and Waveform Times

The synchronization of a multi-frame X-Ray image with a waveform (e.g., ECG, pressure, or respiration) encoded in a different SOP Instance is managed through the attributes of the Synchronization Module (see Section C.7.4.2) of the Frame of Reference IE.

### Note

The use of a Curve IE within the X-Ray IODs was previously defined in DICOM (see PS3.3-2004). That use has been retired in favor of encoding waveform data in a separate IOD.

###### C.8.7.1.1.12 Frame Dimension Pointer

Frame Dimension Pointer (0028,000A) identifies attributes that vary or increment with each frame, and are clinically significant for viewing or processing the image. This is intended for SOP Instances whose preferred clinical presentation is dependent on frame relationships other than simply time.

Defined Terms for multi-frame cine from the Cine Module (see Section C.7.6.5) are:

00181063H

  Frame Time (0018,1063)

00181065H

  Frame Time Vector (0018,1065)

Defined Terms for rotational acquisition from the XA Positioner Module (see Section C.8.7.5) are:

00181520H

  Positioner Primary Angle Increment (0018,1520)

00181521H

  Positioner Secondary Angle Increment (0018,1521)

Defined Terms for stepped acquisition from the X-Ray Table Module (see Section C.8.7.4) are:

00181135H

  Table Vertical Increment (0018,1135)

00181137H

  Table Longitudinal Increment (0018,1137)

00181136H

  Table Lateral Increment (0018,1136)

Defined Terms for an arbitrary labeled increment:

00182002H

  Frame Label Vector (0018,2002)

### Note

1. Previous editions of the standard did not include the optional Frame Dimension Pointer (0028,000A), but instead depended entirely on the mandatory Frame Increment Pointer (0028,0009), and envisaged that only time and no other dimension would relate frames. Image creators that add the Frame Dimension Pointer (0028,000A) must anticipate that many implementations will ignore or discard this attribute when displaying or storing images and continue to assume that frames are temporally related.

2. Frame Time (0018,1063) or Frame Time Vector (0018,1065) will also be present and will contain appropriate values consistent with the times of acquisition of the frames.

###### C.8.7.1.1.13 Referenced Image Sequence

When Image Type (0008,0008) Value 3 is BIPLANE A or BIPLANE B, Referenced Image Sequence (0008,1140) shall be used to identify the corresponding SOP Instance of the Biplane acquisition. In this case, either:

- only a single item shall be present, or

- multiple items may be present, each with the Purpose of Reference Code Sequence (0040,A170) present, and only the first item having the Purpose of Reference value (121314, DCM, "Other image of biplane pair").

The Referenced Frame Number (0008,1160) attribute shall not be present in the Item that references the corresponding SOP Instance of the Biplane acquisition.

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