C.8.17.2 Ophthalmic Photography Image Module

Table C.8.17.2-1 specifies the Attributes that describe an Ophthalmic Photography Image produced by Ophthalmic Photography equipment (OP) imaging Modalities.

Table C.8.17.2-1 OPHTHALMIC PHOTOGRAPHY IMAGE MODULE ATTRIBUTES

Attribute Name Tag Type Attribute Description
Image Type (0008,0008) 1 Image identification characteristics. See C.8.17.2.1.4 for specialization.
Instance Number (0020,0013) 1 A number that identifies this image.
Samples per Pixel (0028,0002) 1 Number of samples (planes) in this image. Enumerated values: 1 or 3. See C.8.17.2.1.2 for further explanation.
Samples per Pixel Used (0028,0003) 1C The number of samples (planes) containing information. Enumerated value: 2. Required if different from Samples per Pixel (0028,0002). See section C.8.17.2.1.2
Photometric Interpretation (0028,0004) 1 Specifies the intended interpretation of the pixel data. See section C.8.17.2.1.3
Pixel Representation (0028,0103) 1 Data representation of the pixel samples. Enumerated value: 0
Planar Configuration (0028,0006) 1C Indicates whether the pixel data are sent color-by-plane or color-by-pixel. Required if Samples per Pixel (0028,0002) has a value greater than 1. Enumerated value shall be 0 (color-by-pixel).
Pixel Spacing (0028,0030) 1C Nominal physical distance at the focal plane (in the retina) between the center of each pixel, specified by a numeric pair - adjacent row spacing (delimiter) adjacent column spacing in mm. See 10.7.1.3 for further explanation of the value order. Note: These values are specified as nominal because the physical distance may vary across the field of the images and the lens correction is likely to be imperfect. Required when Acquisition Device Type Code Sequence (0022,0015) contains an item with the value (SRT, R-1021A,”Fundus Camera”). May be present otherwise.
Content Time (0008,0033) 1 The time the image pixel data creation started.
Content Date (0008,0023) 1 The date the image pixel data creation started.
Acquisition DateTime (0008,002A) 1C The date and time that the acquisition of data started. Note: The synchronization of this time with an external clock is specified in the synchronization Module in Acquisition Time Synchronized (0018,1800). Required if Image Type (0008,0008) Value 1 is ORIGINAL. May be present otherwise.
Source Image Sequence (0008,2112) 2C A Sequence that identifies the Images that were used to derive this Image. Required if Image Type Value 1 is DERIVED. Zero or more items shall be included in this sequence. See C.7.6.1.1.4 for further explanation.
>Include Image SOP Instance Reference Macro, Table 10-3
>Purpose of Reference Code Sequence (0040,A170) 1 Describes the purpose for which the reference is made, that is what role the source image or frame(s) played in the derivation of this image. Only a single Item shall be included in this sequence.
>>Include ‘Code Sequence Macro’ Table 8.8-1 Defined CID 7202.
Lossy Image Compression (0028,2110) 1 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
Lossy Image Compression Ratio (0028,2112) 1C Describes the approximate lossy compression ratio(s) that have been applied to this image. See C.7.6.1.1.5 for further explanation. May be multivalued if successive lossy compression steps have been applied. Notes: 1. For example, a compression ratio of 30:1 would be described in this Attribute with a single value of 30. 2. For historical reasons, the lossy compression ratio should also be described in Derivation Description (0008,2111) Required if Lossy Image Compression (0028,2110) has a value of “01”.
Lossy Image Compression Method (0028,2114) 1C A label for the lossy compression method(s) that have been applied to this image. See C.7.6.1.1.5 for further explanation. May be multivalued if successive lossy compression steps have been applied; the value order shall correspond to the values of Lossy Image Compression Ratio (0028,2112). Required if Lossy Image Compression (0028,2110) has a value of “01”. Note: For historical reasons, the lossy compression method should also be described in Derivation Description (0008,2111).
Presentation LUT Shape (2050,0020) 1C Specifies an identity transformation for the Presentation LUT, 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. Required if Photometric Interpretation (0028,0004) is MONOCHROME2
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
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 Value: YES NO
Recognizable Visual Features (0028,0302) 3 Indicates whether or not the image contains sufficiently recognizable visual features to allow the image or a reconstruction from a set of images to identify the patient. Enumerated Values: YES NO If this Attribute is absent, then the image may or may not contain recognizable visual features.

C.8.17.2.1 Ophthalmic Photography Image Module Attribute Descriptions

C.8.17.2.1.1 Referenced Image Sequence

The Referenced Image Sequence (0008,1140) in the General Image Module (Section C.7.6.1) shall not convey stereoscopic information, which instead shall be encoded using the Stereometric Relationship IOD.

C.8.17.2.1.2 Samples per Pixel and Samples per Pixel Used

Samples per Pixel (0028,0002) shall be 1 or 3.

Cameras producing 2-color images are required to use a value of 3 for Samples per Pixel (0028,0002) and a value of 2 for Samples per Pixel Used (0028,0003). For 2-color images with a RGB Photometric Interpretation, the R and G channel shall be used and the B channel shall have all values set to zero.

Note: In the case of Photometric Interpretations typically used for compression such as YBR_FULL_422, the encoding will be as if the RGB values were transformed to YCbCr.

C.8.17.2.1.3 Photometric Interpretation

Specifies the intended interpretation of the pixel data. Enumerated Values shall be:

MONOCHROME2

RGB

YBR_FULL_422

YBR_PARTIAL_420

YBR_ICT

YBR_RCT

C.8.17.2.1.4 Image Type

The Image Type attribute (0008,0008) (General Image Module, C.7.6.1) identifies important image characteristics in a multiple valued data element. For the Ophthalmic Photography Image IOD, Image Type is specified as a Type 1 attribute and further 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;

  1. Value 2 shall identify the Patient Examination Characteristics in accordance with Section C.7.6.1.1.2; Enumerated Value is: PRIMARY

  2. Value 3 shall only be present if Value 1 is DERIVED; Defined Terms: MONTAGE.

  3. Value 4 (optionally present) shall identify the type of test performed for image acquisition. Defined terms:

COLOR - a picture take at “white” light; no filters applied

REDFREE - a picture take at “green” illumination light; or just the green channel of a color sensor

RED - a picture take at “red” illumination light; or just the red channel of a color sensor

BLUE - a picture take at “blue” illumination light; or just the blue channel of a color sensor

FA- fluorescein injected; a picture taken at fluorescein exciting illumination light; a filter passing just the emitted wavelength to sensor applied

ICG - Indocyanine green injected; a picture taken at Indocyanine green exciting illumination light; a filter passing just the emitted wavelength to sensor applied

Note: A Montage Image is constructed out of several individual images, which also can be exchanged separately. The images used to create the montage image will be included in the source image sequence if those images are also exchanged. A Montage Image is identified as Image Type DERIVED\PRIMARY\MONTAGE