C.8.30.2 Corneal Topography Map Image Module
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#### C.8.30.2 Corneal Topography Map Image Module

Table C.8.30.2-1 specifies the Attributes that describe an Image produced by corneal topography mapping devices.

Table C.8.30.2-1. Corneal Topography Map Image Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
Instance Number | (0020,0013) | 1 | A number that identifies this instance.
Content Date | (0008,0023) | 1 | The date the data creation was started.
Content Time | (0008,0033) | 1 | The time the data creation was started.
Acquisition DateTime | (0008,002A) | 1 | The date and time that the acquisition of data that resulted in this image started. ### Note The synchronization of this time with an external clock is specified in the Synchronization Module in Acquisition Time Synchronized (0018,1800).
Image Type | (0008,0008) | 1 | Image identification characteristics. See Section C.8.30.2.1.1 for specialization.
Samples Per Pixel | (0028,0002) | 1 | Number of samples (planes) in this image. See Section C.7.6.3.1.1 for further explanation. Enumerated Values: 1
Photometric Interpretation | (0028,0004) | 1 | Specified the intended interpretation of the pixel data. See Section C.7.6.3.1.2 for further explanation. Enumerated Values: PALETTE COLOR
Pixel Representation | (0028,0103) | 1 | Data representation of pixel samples. Enumerated Values: 0000H unsigned integer
Include Table 10-10 “Basic Pixel Spacing Calibration Macro Attributes” |
Pixel Aspect Ratio | (0028,0034) | 1 | Ratio of the vertical size and horizontal size of the pixels in the image specified by a pair of integer values where the first value is the vertical pixel size, and the second value is the horizontal pixel size.
Bits Allocated | (0028,0100) | 1 | Number of bits allocated for each pixel sample. Each sample shall have the same number of bits allocated. See PS3.5 for further explanation. Enumerated Values: 8 16
Bits Stored | (0028,0101) | 1 | Number of bits stored for each pixel sample. Enumerated Values: 8 16
High Bit | (0028,0102) | 1 | Most significant bit for pixel sample data. Each sample shall have the same high bit. See PS3.5 for further explanation. Enumerated Values: 7 if Bits Stored (0028,0101) = 8 15 if Bits Stored (0028,0101) = 16
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 Section C.7.6.1.1.5 for further explanation.
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 for further explanation. May be multi-valued if successive lossy compression steps have been applied; the value order shall correspond to the values of Lossy Image Compression Method (0028,2114). ### Note For example, a compression ratio of 30:1 would be described in this Attribute with a single value of 30. For historical reasons, the lossy compression ratio may also be described in Derivation Description (0008,2111). Required if Lossy Image Compression (0028,2110) is "01".
Lossy Image Compression Method | (0028,2114) | 1C | A label for the lossy compression method(s) that have been applied to this image. See Section C.7.6.1.1.5 for further explanation. May be multi-valued if successive lossy compression steps have been applied; the value order shall correspond to the values of Lossy Image Compression Ratio (0028,2112). ### Note For historical reasons, the lossy compression method may also be described in Derivation Description (0008,2111). Required if Lossy Image Compression (0028,2110) is "01".
Burned In Annotation | (0028,0301) | 1 | Indicates that the image does not contain burned in annotation to identify the patient and date the image was acquired. Enumerated Values: NO
Recognizable Visual Features | (0028,0302) | 1 | 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 ### Note Corneal topography is similar to finger prints as it is unique to individuals. Therefore, it could be used by a trained person or an expert system to identify the patient.
Image Laterality | (0020,0062) | 1 | Laterality of object imaged (as described in Anatomic Region Sequence (0008,2218)) examined. Enumerated Values: R right eye L left eye ### Note This Attribute is mandatory, in order to ensure that images may be positioned correctly relative to one another for display. Shall be consistent with any laterality information contained in Primary Anatomic Structure Modifier Sequence (0008,2230), if present. ### Note Laterality (0020,0060) is a Series level Attribute and must be the same for all Images in the Series, hence it must be absent.
Include Table C.7.6.16-12 “Real World Value Mapping Macro Attributes” | Defined CID for Measurement Units Code Sequence is 4267
Include Table 10-5 “General Anatomy Mandatory Macro Attributes” | The concept code for Anatomic Region Sequence (0008,2218) shall be (T-AA000, SRT, "Eye"), and Defined CID 244 “Laterality” shall be used for Anatomic Region Modifier Sequence (0008,2220). Defined CID 4266 “Ophthalmic Anatomic Structure Reference Point” shall be used for Primary Anatomic Structure Sequence (0008,2228). Only a single Item shall be permitted in this sequence. ### Note Although Primary Anatomic Structure Sequence (0008,2228) is Type 3, it is important to convey this information if able to be determined.

##### C.8.30.2.1 Corneal Topography Map Image Module Attribute Descriptions

###### C.8.30.2.1.1 Image Type

For Corneal Topography Maps, Image Type (0008,0008) is specified to be Type 1.

Defined Terms for Image Type Value 3:

CORNEAL_TOPO

  Identifies a topographic map of the cornea

###### C.8.30.2.1.2 Corneal Topography Map Real World Value and Image Transformations

The Corneal Topography Map SOP Class supports a sequence of transformations that completely define the conversion of a stored image into a displayed image.

The sequence of transformations from corneal measurements to a displayable image is explicitly defined in Figure C.8.30.2.1-1. Figure C.8.30.2.1-1 also conveys the transformation to display the scaling of the color map using its Real World Value Macro (see Table C.7.6.16-12 for more details on the Real World Value Macro).

Figure C.8.30.2.1-1. Corneal Topography Map Real World Value and Image Transformation Pipeline

An SCP of the Corneal Topography Map Storage SOP Class, when rendering SOP Instances of the Class shall apply the image transformations (i.e., Palette Color LUT) and the Real World Value LUT to display the annotated color scale. The annotated color scale shall conform to the "ISO Standard 19980 - Ophthalmic instruments - Corneal topographers, second edition, section B.4 Standardized colour Scale."

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