DICOM PS3.3 2016a - Information Object Definitions

C.8.17.12 Wide Field Ophthalmic Photography 3D Coordinates Module
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#### C.8.17.12 Wide Field Ophthalmic Photography 3D Coordinates Module

Table C.8.17.12-1 specifies the Attributes that describe the Wide Field Ophthalmic Photography 3D Coordinates Module.

Table C.8.17.12-1. Wide Field Ophthalmic Photography 3D Coordinates Module Attributes

Attribute Name | Tag | Type | Attribute Description
--- | --- | --- | ---
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). Only a single Item shall be included in Anatomic Region Modifier Sequence (0008,2220).
Transformation Method Code Sequence | (0022,1512) | 1 | Method used to map the 2D Pixel Image data in this SOP Instance to the 3D Cartesian coordinates in the Dimensional to Two Three Dimensional Map Sequence (0022,1518). Only a single Item shall be included in this Sequence. See Section C.8.17.12.1.1 for further explanation.
>>Include Table 8.8-1 “Code Sequence Macro Attributes” | Defined CID 4245 “Wide Field Ophthalmic Photography Transformation Method”
Transformation Algorithm Sequence | (0022,1513) | 1 | Software algorithm that performed the mapping. Only a single Item shall be included in this Sequence.
>Include Table 10-19 “Algorithm Identification Macro Attributes” |
Ophthalmic Axial Length | (0022,1019) | 1 | The axial length measurement used when performing the 2D pixel imagemapping into 3D Cartesian coordinates, in mm.
Ophthalmic Axial Length Method | (0022,1515) | 1 | The method used to obtain the Ophthalmic Axial Length. Enumerated values: MEASURED Measured axial length. ESTIMATED An estimated value based upon performing the examination (i.e. based upon surrogate markers of axial length). POPULATION A length that represents a population norm (i.e. not based upon a measured axial length or surrogate markers of axial length).
Ophthalmic FOV | (0022,1517) | 3 | The field of view used to capture the ophthalmic image, in degrees. The field of view is the maximum image size displayed on the image plane, expressed as the angle subtended at the exit pupil of the eye by the maximum dimension 2r (where r equals the radius).
Two Dimensional to Three Dimensional Map Sequence | (0022,1518) | 1 | A sparsely sampled map of 2D image pixels (with sub pixel resolution) to 3D coordinates. Each frame shall be referenced once and only once in this Sequence in Referenced Frame Numbers (0040,A136). One or more Items shall be included in this Sequence.
>Referenced Frame Numbers | (0040,A136) | 1 | References one or more frames within this SOP Instance to which this sequence item applies. The first frame shall be denoted as frame number one.
>Number of Map Points | (0022,1530) | 1 | The number of points in the map. Shall include one or more points.
>Two Dimensional to Three Dimensional Map Data | (0022,1531) | 1 | See Section C.8.17.12.1.2 for further explanation.

##### C.8.17.12.1 Wide Field Ophthalmic Photography 3D Coordinates Attribute Descriptions

###### C.8.17.12.1.1 Transformation Method Code Sequence

If Transformation Method Code Sequence (0022,1512) is (DCM, 111791, "Spherical projection") all the coordinates in the Two Dimensional to Three Dimensional Map Data (0022,1531) shall lie on a sphere with a diameter that shall be equal to Ophthalmic Axial Length (0022,1019).

If Transformation Method Code Sequence (0022,1512) is (DCM, 111792, "Surface contour mapping") the coordinates in the Two Dimensional to Three Dimensional Map Data (0022,1531) are based upon the contour of the eye, therefore it cannot be assumed to be a spherical surface.

###### C.8.17.12.1.2 Two Dimensional to Three Dimensional Map Data

Two Dimensional to Three Dimensional Map Data (0022,1531) is used to convey a sparsely sampled map of 2D image pixels (with sub pixel resolution) to 3D coordinates.

The origin of the 3D points shall be the Ophthalmic Coordinate System which is based upon the corneal vertex (i.e. the x, y and z coordinates of 0.0, 0.0, 0.0, in mm). See Section C.8.30.3.1.4.

All data points are encoded as a floating point 5-tuple where the values are:

- 1st value = 2D horizontal location (a sub pixel location between 0 and number of columns)

- 2nd value = 2D vertical location (a sub pixel location between 0 and number of rows)

- 3rd value = x 3D-coordinate

- 4th value = y 3D-coordinate

- 5th value = z 3D-coordinate

The ordering is 2D horizontal location1, 2D vertical location1, 3Dx1, 3Dy1, 3Dz1, … 2D horizontal locationn, 2D vertical locationn, 3Dxn, 3Dyn, 3Dzn.

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DICOM PS3.3 2016a - Information Object Definitions