C.8.7.1 X-Ray Image Module

Table C.8-26X-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 C.7.6.6). Specialized for X-Ray as Enumerated Value: 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. Enumerated Values: 00 = Image has NOT been subjected to lossy compression. 01 = Image has been subjected to lossy compression. See C.7.6.1.1.5 Required if Lossy Compression has been performed on the Image.
Image Type (0008,0008) 1 Image identification characteristics. See 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 'General Anatomy Optional Macro' Table 10-7 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 ‘Image SOP Instance Reference Macro’ Table 10-3
>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 Code Sequence Macro Table 8.8-1 Defined Context ID 7201
Derivation Description (0008,2111) 3 A text description of how this image was derived. See 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 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 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:

a. Value 1 shall identify the Pixel Data Characteristics in accordance with Section C.7.6.1.1.2; Enumerated Values are: ORIGINAL and DERIVED;

b. Value 2 shall identify the Patient Examination Characteristics in accordance with Section C.7.6.1.1.2; Enumerated Values are: PRIMARY and SECONDARY.

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

c. Value 3 shall identify the image set in terms of the imaging planes. Enumerated Values are:

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

d. 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 are:

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 which was used during the acquisition of the image. Defined Terms are:

EKG EKG Event Trigger
PHY Physiological Event Trigger
TOMO Tomography
CHASE Bolus Chasing
STEP Stepping
ROTA Rotation

C.8.7.1.1.5 Derivation Description

If an Image is identified to be a Derived image (see C.8.7.1.1.1 Image Type), 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

For X-Ray Images, Bits Allocated (0028,0100) shall have the Enumerated Value of 8 or 16.

C.8.7.1.1.7 Bits Stored

For X-Ray Images, Bits Stored (0028,0101) shall have the Enumerated Values of 8, 10, 12, or 16.

C.8.7.1.1.8 High Bit

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

C.8.7.1.1.9 Synchronization of Frame and Waveform Times

The synchronization of a multiframe 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 which 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 multiframe cine from the Cine Module (see 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 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 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)

Notes: 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:

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