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.188.8.131.52.2; Enumerated Values are: ORIGINAL and DERIVED;
b. Value 2 shall identify the Patient Examination Characteristics in accordance with Section C.184.108.40.206.2; 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).
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.|
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).
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|
If an Image is identified to be a Derived image (see C.220.127.116.11.1 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.
For X-Ray Images, Bits Allocated (0028,0100) shall have the Enumerated Value of 8 or 16.
For X-Ray Images, Bits Stored (0028,0101) shall have the Enumerated Values of 8, 10, 12, or 16.
For X-Ray Images, High Bit (0028,0102) shall have the Enumerated Value of one less than the value in Bit Stored.
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.
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.
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.