C.8.17 Ophthalmic Photography and Tomography Modules

C.8.17.1 Ophthalmic Photography Series Module

Table C.8.17.1-1 specifies the attributes that describe an Ophthalmic Photography Series.

Table C.8.17.1-1OPHTHALMIC PHOTOGRAPHY SERIES MODULE ATTRIBUTES

Attribute Name Tag Type Attribute Description
Modality (0008,0060) 1 Source equipment that produced the Ophthalmic Photography Series. Enumerated Value: OP

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

C.8.17.3 Ophthalmic Photographic Parameters Module

This Module describes equipment used to create original images.

Table C.8.17.3-1OPHTHALMIC PHOTOGRAPHIC PARAMETERS MODULE ATTRIBUTES

Attribute Name Tag Type Attribute Description
Acquisition Device Type Code Sequence (0022,0015) 1 Describes the type of acquisition device. Only a single item shall be included in this sequence.
>Include ‘Code Sequence Macro’ Table 8.8.1 Baseline CID 4202
Illumination Type Code Sequence (0022,0016) 2 Coded value for illumination. Zero or one item shall be included in this sequence.
>Include ‘Code Sequence Macro’ Table 8.8.1 Baseline CID 4203
Light Path Filter Type Stack Code Sequence (0022,0017) 2 Filters used in the light source path. Zero or more items shall be included in this sequence.
>Include ‘Code Sequence Macro’ Table 8.8.1 Baseline CID 4204
Light Path Filter Pass-Through Wavelength (0022,0001) 3 Nominal pass-through wavelength of light path filter in nm
Light Path Filter Pass Band (0022,0002) 3 Pass band of light path filter in nm. This Attribute has two Values. The first is the shorter and the second the longer wavelength relative to the peak. The values are for the - 3dB nominal (1/2 of peak) pass through intensity. One of the two Values may be zero length, in which case it is a cutoff filter.
Image Path Filter Type Stack Code Sequence (0022,0018) 2 Describes stack of filters used in image path. Zero or more items shall be included in this sequence.
>Include ‘Code Sequence Macro’ Table 8.8.1 Baseline CID 4204
Image Path Filter Pass-Through Wavelength (0022,0003) 3 Nominal pass-through wavelength of image path filter in nm
Image Path Filter Pass Band (0022,0004) 3 Pass band of image path filter in nm. This Attribute has two Values. The first is the shorter and the second the longer wavelength relative to the peak. The values are for the - 3dB nominal (1/2 of peak) pass through intensity. One of the two Values may be zero length, in which case it is a cutoff filter
Lenses Code Sequence (0022,0019) 2 Lenses that were used during the image acquisition. Zero or more items shall be included in this sequence.
>Include ‘Code Sequence Macro’ Table 8.8.1 Baseline CID 4205
Detector Type (0018,7004) 2 Type of detector used for creating this image. Defined terms: CCD = Charge Coupled Devices CMOS = Complementary Metal Oxide Semiconductor
Channel Description Code Sequence (0022,001A) 1C Describes the light color used for each channel to generate the image. Required if this differs from the natural interpretation. Note: Interpretation and representation of RGB images rely on the assumption that the red channel really contains the red wavelength range of illumination light, the blue channel the blue wavelength range, etc. Some modalities use the RGB Photometric Interpretation as a container representing 3 channels of any illumination wavelength. Shall have the same number of items as the Value of Samples per Pixel Used (0028,0003) if present, or otherwise the value of Samples per Pixel (0028,0002). The channels shall be described in the order in which the channels are encoded.
>Include ‘Code Sequence Macro’ Table 8.8.1 Baseline CID 4206
Camera Angle of View (0022,001E) 3 The aperture angle of the camera, in degrees

C.8.17.4 Ophthalmic Photography Acquisition Parameters Module

This Module describes patient clinical conditions related to the image acquisition.

Table C.8.17.4-1OPHTHALMIC PHOTOGRAPHY ACQUISITION PARAMETERS MODULE ATTRIBUTES

Attribute Name Tag Type Attribute Description
Patient Eye Movement Commanded (0022,0005) 2 Enumerated Values: YES NO
Patient Eye Movement Command Code Sequence (0022,0006) 1C Coded value for patient movement or orientation, which is the intent, and not necessarily the result, based on what the patient is capable of. Required if the value of Patient Eye Movement Commanded (0022,0005) is YES. Only a single item shall be included in this sequence.
>Include ‘Code Sequence Macro’ Table 8.8.1 Baseline CID 4201
Include ‘Ophthalmic Acquisition Parameters Macro’ Table C.8.17.8-2

C.8.17.5 Ocular Region Imaged Module

Table C.8.17.5-1 contains IOD Attributes that describe the anatomy contained in an Ophthalmic Photography or Ophthalmic Tomography IOD.

Table C.8.17.5-1OCULAR REGION IMAGED MODULE ATTRIBUTES

Attribute Name Tag Type Attribute Description
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 B = both left and right eye 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. Since most Ophthalmic Photographic Image studies contain images of both eyes, the series level attribute will rarely be present.
Relative Image Position Code Sequence (0022,001D) 3 The position of this image on the retina (as defined by a specified nomenclature; the nomenclature is implicit in the code used). Only a single Item is permitted in this sequence.
>Include ‘Code Sequence Macro’ Table 8.8.1 Baseline Context ID 4207
Include 'General Anatomy Mandatory Macro' Table 10-5 Defined Context ID 4209 for Anatomic Region Sequence

C.8.17.6 Ophthalmic Tomography Series Module

Table C.8.17.6-1 specifies the Attributes that identify and describe general information about the Ophthalmic Tomography Series.

Table C.8.17.6-1OPHTHALMIC TOMOGRAPHY SERIES MODULE ATTRIBUTES

Attribute Name Tag Type Attribute Description
Modality (0008,0060) 1 Type of equipment that originally acquired the data used to create the images in this Series. Enumerated Values: OPT See section C.7.3.1.1.1 for further explanation.
Series Number (0020,0011) 1 A number that identifies this Series.
Referenced Performed Procedure Step Sequence (0008,1111) 1C Uniquely identifies the Performed Procedure Step SOP Instance to which the Series is related (e.g. a Modality or General-Purpose Performed Procedure Step SOP Instance). Only a single Item shall be included in this sequence. Required if the Modality Performed Procedure Step SOP Class or General Purpose Performed Procedure Step SOP Class is supported.
>Include ‘SOP Instance Reference Macro' Table 10-11

C.8.17.7 Ophthalmic Tomography Image Module

Table C.8.17.7-1 specifies the Attributes that describe an Image produced by Ophthalmic Tomography imaging modalities.

Table C.8.17.7-1OPHTHALMIC TOMOGRAPHY IMAGE MODULE ATTRIBUTES

Attribute Name Tag Type Attribute Description
Image Type (0008,0008) 1 Image identification characteristics. See C.7.6.1.1.2 for Enumerated Values and Defined Terms and further explanation.
Samples Per Pixel (0028,0002) 1 Number of samples (planes) in this image. See C.7.6.3.1.1 for further explanation. Value shall be 1.
Acquisition DateTime (0008,002A) 1 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) .
Acquisition Duration (0018,9073) 1C The scan time in seconds used to create all frames of an Ophthalmic Tomography image. Required if Image Type (0008,0008) Value 1 is ORIGINAL. May be present otherwise.
Acquisition Number (0020,0012) 1 A number identifying the single continuous gathering of data over a period of time which resulted in this image.
Photometric Interpretation (0028,0004) 1 Specifies the intended interpretation of the pixel data. Enumerated Value shall be: MONOCHROME2
Pixel Representation (0028,0103) 1 Data representation of pixel samples. Enumerated Value shall be 0.
Bits Allocated (0028,0100) 1 Number of bits allocated for each pixel sample. Each sample shall have the same number of bits allocated. Bits Allocated (0028,0100) shall be 8 or 16
Bits Stored (0028,0101) 1 Number of bits stored for each pixel sample. Each sample shall have the same number of bits stored. Bits Stored (0028,0101) shall be 8, 12 or 16
High Bit (0028,0102) 1 Most significant bit for pixel sample data. Each sample shall have the same high bit. High Bit (0028,0102) shall be one less than Bits Stored
Presentation LUT Shape (2050,0020) 1 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.
Lossy Image Compression (0028,2110) 1 Specifies whether an Image has undergone lossy compression (at a point in its lifetime). Enumerated Values: 00 = Image has NOT been subjected to lossy compression. 01 = Image has been subjected to lossy compression. Once this tag has been set to 01 it shall not be reset. If this tag is empty, no information is explicitly available. 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. Required when compression has been applied. 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).
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 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). 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).
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: 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.
Concatenation Frame Offset Number (0020,9228) 1 Offset of the first frame in a multi-frame image of a concatenation. Value shall be 0.
In-concatenation Number (0020,9162) 1 Identifier for one SOP Instance belonging to a concatenation. Value shall be 1.
In-concatenation Total Number (0020,9163) 1 The number of SOP Instances sharing the same Concatenation UID (0020,9161). Value Shall be 1.
Image Comments (0020,4000) 3 User-defined comments about the image

The value constraints on Concatenation Frame Offset Number (0020,9228), In-concatenation Number (0020,9162), and In-concatenation Total Number (0020,9163) have the effect of requiring the entire image to be in one concatenation.

C.8.17.8 Ophthalmic Tomography Acquisition Parameters Module

Table C.8.17.8-1 describes patient clinical conditions related to an Ophthalmic Tomography image acquisition.

Table C.8.17.8-1OPHTHALMIC TOMOGRAPHY ACQUISITION PARAMETERS MODULE ATTRIBUTES

Attribute Name Tag Type Attribute Description
Axial Length of the Eye (0022,0030) 2 Axial length of the eye in mm.
Horizontal Field of View (0022,000C) 2 The horizontal field of view in degrees
Include ‘Ophthalmic Acquisition Parameters Macro’ Table C.8.17.8-2

Table C.8.17.8-2OPHTHALMIC ACQUISITION PARAMETERS MACRO

Attribute Name Tag Type Attribute Description
Refractive State Sequence (0022,001B) 2 The refractive state of the imaged eye at the time of acquisition. Zero or one Item shall be included in this sequence. Zero length means the refractive state was not measured.
>Spherical Lens Power (0022,0007) 1 Sphere value in diopters
>Cylinder Lens Power (0022,0008) 1 Cylinder value in diopters
>Cylinder Axis (0022,0009) 1 Axis value in degrees
Emmetropic Magnification (0022,000A) 2 Emmetropic magnification value (dimensionless). Zero length means the emmetropic magnification was not measured.
Intra Ocular Pressure (0022,000B) 2 Value of intraocular pressure in mmHg. Zero length means the pressure was not measured
Pupil Dilated (0022,000D) 2 Whether or not the patient’s pupils were pharmacologically dilated for this acquisition. Enumerated Values: YES NO If this tag is empty, no information is available.
Mydriatic Agent Sequence (0022,0058) 2C Information about the agent administered. Zero or more items shall be included in this sequence. Note: An empty sequence indicates that an agent was used for dilation, but the name was not entered. Required if the value of Pupil Dilated (0022,000D) is YES.
>Mydriatic Agent Code Sequence (0022,001C) 1 The actual agent administered to dilate the pupil. Only a single Item shall be included in this sequence.
>>Include ‘Code Sequence Macro’ Table 8.8-1 Baseline CID 4208.
>Mydriatic Agent Concentration (0022,004E) 3 The concentration of the agent.
>Mydriatic Agent Concentration Units Sequence (0022,0042) 1C Units of measure for the Mydriatic Agent Concentration. Only a single Item shall be included in this sequence. Required if Mydriatic Agent Concentration (0022,004E) is present.
>>Include 'Code Sequence Macro' Table 8.8-1. Defined CID 3082
Degree of Dilation (0022,000E) 2C The degree of the dilation in mm. Required if the value of Pupil Dilated (0022,000D) is YES.

C.8.17.9 Ophthalmic Tomography Parameters Module

Table C.8.17.9-1 describes the parameters and characteristics of the acquisition device related to an Ophthalmic Tomography image acquisition.

Table C.8.17.9-1OPHTHALMIC TOMOGRAPHY PARAMETERS MODULE ATTRIBUTES

Attribute Name Tag Type Attribute Description
Acquisition Device Type Code Sequence (0022,0015) 1 Describes the type of acquisition device. Only a single item shall be included in this sequence.
>Include ‘Code Sequence Macro’ Table 8.8-1 Baseline CID 4210
Light Path Filter Type Stack Code Sequence (0022,0017) 2 Filters used in the light source path. Zero or more items shall be included in this sequence.
>Include ‘Code Sequence Macro’ Table 8.8-1 Baseline CID 4204
>Light Path Filter Pass-Through Wavelength (0022,0001) 3 Nominal pass-through wavelength of light path filter in nm
>Light Path Filter Pass Band (0022,0002) 3 Pass band of light path filter in nm. This Attribute has two Values. The first is the shorter and the second the longer wavelength relative to the peak. The values are for the - 3dB nominal (1/2 of peak) pass through intensity. One of the two Values may be zero length, in which case it is a cutoff filter.
Detector Type (0018,7004) 1 Type of detector used for creating this image. Defined terms: CCD = Charge Coupled Device CMOS = Complementary Metal Oxide Semiconductor PHOTO = Photodetector INT = Interferometer
Illumination Wave Length (0022,0055) 1C Wavelength of the illuminator in nm. Required if Acquisition Device Type Code Sequence (0022,0015) contains an item with the value (A-00FBE, SRT, ”Optical Coherence Tomography Scanner”). May be present otherwise.
Illumination Power (0022,0056) 1C Power of the illuminator in microwatts at corneal plane. Required if Acquisition Device Type Code Sequence (0022,0015) contains an item with the value (SRT, A-00FBE,”Optical Coherence Tomography Scanner”). May be present otherwise.
Illumination Bandwidth (0022,0057) 1C Bandwidth of the illuminator in nm. Required if Acquisition Device Type Code Sequence (0022,0015) contains an item with the value (A-00FBE, SRT, ”Optical Coherence Tomography Scanner”). May be present otherwise.
Depth Spatial Resolution (0022,0035) 1C The inherent limiting resolution in microns for depth of the acquisition equipment for high contrast objects for the data gathering and reconstruction technique chosen. If variable, the value at the center of the scanning volume. Required if Acquisition Device Type Code Sequence (0022,0015) contains an item with the value (A-00FBE, SRT, ”Optical Coherence Tomography Scanner”). May be present otherwise.
Maximum Depth Distortion (0022,0036) 1C Maximum distortion in depth direction in % of Depth Spatial Resolution. Required if Acquisition Device Type Code Sequence (0022,0015) contains an item with the value (SRT, A-00FBE,”Optical Coherence Tomography Scanner”). May be present otherwise.
Along-scan Spatial Resolution (0022,0037) 1C The inherent limiting resolution in microns of the acquisition equipment in the direction of a row. Required if Acquisition Device Type Code Sequence (0022,0015) contains an item with the value (A-00FBE, SRT, ”Optical Coherence Tomography Scanner”). May be present otherwise.
Maximum Along-scan Distortion (0022,0038) 1C Maximum distortion in along-scan direction in % of Along-scan Spatial Resolution. Required if Acquisition Device Type Code Sequence (0022,0015) contains an item with the value (A-00FBE, SRT, ”Optical Coherence Tomography Scanner”). May be present otherwise.
Across-scan Spatial Resolution (0022,0048) 1C The inherent limiting resolution in microns of the acquisition equipment perpendicular to the slice. Required if Acquisition Device Type Code Sequence (0022,0015) contains an item with the value (A-00FBE, SRT, ”Optical Coherence Tomography Scanner”). May be present otherwise.
Maximum Across-scan Distortion (0022,0049) 1C Maximum distortion in across-scan direction in % of cross-scan Spatial Resolution. Required if Acquisition Device Type Code Sequence (0022,0015) contains an item with the value (A-00FBE, SRT, ”Optical Coherence Tomography Scanner”). May be present otherwise.

C.8.17.10 Ophthalmic Tomography Functional Group Macros

C.8.17.10.1 Ophthalmic Frame Location Macro

Table C.8.17.10-1 specifies the attributes of the Ophthalmic Frame Location Functional Group Macro. This is used to provide a frame location relative to one or more referenced images. This macro describes a frame perpendicular or parallel to the reference image; it describes column locations for frames that are scanned either uniformly along a line segment, or with a non-uniform spacing along any trajectory in the reference image.

Table C.8.17.10-1

Ophthalmic Frame Location Macro Attributes

Attribute Name Tag Type Attribute Description
Ophthalmic Frame Location Sequence (0022,0031) 1 Specifies the column locations for this frame in terms of locations on a referenced image. One or more Items shall be included in this sequence.
>Include ‘Image SOP Instance Reference Macro’ Table 10-3 Defined Term for Purpose of Reference is (121311, DCM, ”Localizer”)
>Reference Coordinates (0022,0032) 1 Image coordinates for the points on the referenced image that correspond to the points on this frame. See section C.8.17.10.1.1.
>Depth of Transverse Image (0022,0041) 2C Relative position in microns signifying the location of a Transverse image in the z-axis. Required if Ophthalmic Image Orientation (0022,0039) is TRANSVERSE.
>Ophthalmic Image Orientation (0022,0039) 1 Enumerated Values: LINEAR NONLINEAR TRANSVERSE

C.8.17.10.1.1 Reference Coordinates

A frame can be described in terms of its “position” on another image. In the case of ophthalmic tomography (OPT) images with longitudinal orientation, the OPT image corresponds to a vertical slice along a trajectory on the referenced image. Each column of the OPT frame is nominally perpendicular to the image. Therefore, each column of the OPT frame can also correspond to a particular pixel on an associated image. It is normal in OPT analysis to indicate the location of the OPT slice by showing the corresponding pixel locations on the image. For Transverse frames, the position is indicated by two corners of a rectangle.

Note: The simple geometric relationship modules are not practical to use for describing the relationship between OPT and retinal photography images. The retinal surface is highly curved, and the optical path is influenced by the lens and other eye structures. It is impractical to measure all of the geometric and optical properties of the eye to the degree needed to establish the relationship by geometric computation. It is easy to capture a retinal image and the slice path on that image as part of the OPT acquisition.

The OPT columns for a retinal slice are not strictly perpendicular to the retina and there are minor systematic distortions as a result. This DICOM functional group does not attempt to capture the data needed to measure or correct for these effects, except for the presence of the Maximum Along-scan Distortion Attribute (0022,0038).

The relationship between the columns in the image frame and the reference image are illustrated in Figure C.8.17.10-1.

Frames can be captured using a linear scan with uniform column spacing. This permits the column position to be described by giving the endpoints of the line segment that was scanned. Figure C.8.17.10-1 shows such a scan labeled as “OCT Frame 1”. When describing this frame using the Linear Column Locations Functional Group Macro, the sequence attributes would contain:

  1. The Attributes of the Image SOP Instance Reference Macro would point to a frame of the reference image.

  2. The Reference Coordinates (0022,0032) would contain values that give the row and column coordinates for the image pixel on the referenced image that corresponds to the first column of the OPT Frame 1 and the row and column coordinates that corresponds to the last column of the OPT Frame 1.

Frames can also be taken along curved paths, or with non-uniform spacing. These frames cannot be described by just the two endpoints. These frames are described by specifying the referenced image pixel coordinates for each column in the frame. The frame labeled “OCT Frame 2” illustrates this kind of relationship. The Non-linear Column Locations Functional Group Macro description for this frame would contain:

  1. The Attributes of the Image SOP Instance Reference Macro would point to a frame of the reference image.

  2. The Reference Coordinates (0022,0032) would contain 2N integer values. Their contents would be:

1-2 (e,f)

…. other values

2L-1, 2L (g,h)

….. other values

2N-1, 2N (x,y)

A three dimensional OPT raster scan image would be described by a series of Linear Column Location Sequences, one for each frame.

Note: One expected use of column location is the automatic generation of annotation graphics display. The slice location can be indicated and dynamically controlled on the reference image while examining the observed slices. This replaces the relatively inflexible practice of creating a modified retinal image with burned in annotation to indicate the slice locations.

[pic]

Figure C.8.17.10-1: Relationship of Longitudinal (nominally perpendicular) OCT Frames to Reference Frame

In the case of ophthalmic tomography (OPT) images with a transverse orientation, the OPT image corresponds to a sub-rectangle of the reference image. See Figure C.8.17.10-2. The OPT frame is nominally parallel to the reference image. Therefore, each corner of the OPT frame can also correspond to a particular pixel on an associated image. It is assumed that the edges of OPT frame are exactly parallel to the edges of the reference image.

[pic]

Figure C.8.17.10-2: Relationship of Transverse (nominally parallel) OCT Frame to Reference Frame