Supplement xx: Wide Field Ophthalmic Photography Image SOP Class
Page 7
Digital Imaging and Communications in Medicine (DICOM)
Supplement 173: Wide Field Ophthalmic Photographyic Image Storage SOP Classes
Prepared by:
DICOM Standards Committee
1300 N. 17th Street Suite 9001847
Rosslyn, Virginia 22209 USA
VERSION: Draft Pre-Public Comment, June 24, 2014
Developed pursuant to DICOM Work Item: 2013-12-A
Table of Contents
Table of Contents 2
Scope and Field of Application 3
Changes to NEMA Standards Publication PS 3.2-2013 4
Part 2: Conformance 4
Changes to NEMA Standards Publication PS 3.3-2013 5
Part 3: Information Object Definitions Part 3 Additions 5
A.xx Wide Field Ophthalmic Photography Image Information Object Definition 6
A.xx.1 Wide Field Ophthalmic Photography Image IOD Description 6
A.xx.2 Wide Field Ophthalmic Photography Image IOD Entity-Relationship Model 6
A.xx.3 Wide Field Ophthalmic Photography Image IOD Modules 6
A.xx.4 Wide Field Ophthalmic Photography Image IOD Content Constraints 7
Changes to NEMA Standards Publication PS 3.4-2013 13
Part 4: Service Class Specifications 13
B.5 Standard SOP Classes 13
I.4 Media Standard Storage SOP Classes 13
Changes to NEMA Standards Publication PS 3.6-2013 15
Part 6: Data Dictionary 15
Changes to NEMA Standards Publication PS 3.16-2013 16
Part 16: Content Mapping Resource 16
CID 42x1 Wide Field Ophthalmic Photography Projection Method 16
Annex D DICOM Controlled Terminology Definitions (Normative) 17
Annex U Ophthalmology Use Cases (Informative) 18
U.x Wide Field Ophthalmic Use Cases 18
U.x.1 Routine Wide Field Image for Surveillance for Diabetic Retinopathy 18
U.x.2 Patient with Myopia 18
U.x.3 Patient with Diabetes 18
U.x.4 Patient with Diabetes 18
Supplement xx: Wide Field Ophthalmic Photography Image SOP Class
Page 7
Scope and Field of Application
A SOP Class to enable anatomically correct measurements on wide field ophthalmic photography 8-bit and 16 bit images.
Vendors have implemented new technology which enables the acquisition of OP images using wide field fundus photography. Since the back of the eye is approximately a concave sphere, taking a very wide-Field image of it introduces large error in any attempt to measure a lesion in that image (the error is very large when using a single value for the DICOM Pixel Spacing Attribute.). Therefore, DICOM WG 9 (Ophthalmology) has determined that a new Information Object Definition (IOD) is necessary to adequately represent wide field fundus photography. The OP IOD does not address wide fields, varied pixel spacing, and proper measurement of a spherical surface or other method of projection.
Manufacturers of ophthalmic photographic imaging devices have been developing OP images (using a narrow field) for many years in DICOM (ie., these SOP Classes are widely supported by the DICOM ophthalmic community). Therefore, these wide field OP imaging SOP Classes are an extension to already existing narrow field DICOM SOP Classes.
The expected use cases are described below in an informative annex that will become part of the standard.
Open Issues:
1 – Should wide field abilities be added to the Stereo relationship IOD? - No
2 – These wide field IODs use the existing OP IODs and expands them with the modules needed to capture the projection to 3D images. Since, we are expanding the OP object, should we changed the design of the OP object to include the enhanced capabilities such as the functional groups module, etc. (as used by enhanced CT, MR, US, OPT and others). Or should we continue to follow the multi-frame mechanism as already defined by the “narrow field” OP? -
WG9 has decided it is best to follow the currently defined OP multi-frame mechanism. The wide field extension is a feature already supported by multiple vendors and this important feature can be implemented based upon current solutions that are widely implemented by the ophthalmic community. Creating an “Enhanced OP” is a different solution that would require much more time to develop and implement by the vendors, and provides no additional user benefits. Our thoughts are this choice would delay the use of Wide Field images for over 5 years or more (as is quite common when other IODs decided to generate an Enhanced IOD).
3 – Should we support 8 and 16 bit in IODs (as already defined for OP) or combine into one SOP Class? – Decided to define two SOP Classes to be consistent with the current OP SOP Classes. Requiring implementations to support 16 bits (especially 16-bit color) is not widely implemented, therefore we do not wish to “raise the bar” for such a uncommonly used feature.
4 – Can and/or should we use the Deformable Spatial Registration Module to encode the projection 3D Cartesian coordinates? This module is specifically for transforming data into a new grid that enables registration of two data objects. Our objective is to define a space for measurement only and that is defined in a fundamentally different way: it defines x,y,z coordinates in a Euclidean space rather than a transformation field from one grid space to another grid space. Therefore, we are not able to use this module.
Changes to NEMA Standards Publication PS 3.2-2013
Digital Imaging and Communications in Medicine (DICOM)
Part 2: Conformance
Item: Add to table A.1-2 categorizing SOP Classes:
The SOP Classes are categorized as follows:
Table A.1-2
UID VALUES
UID Value / UID NAME / Category… / … / …
1.2.840.10008.5.1.4.1.1.xxxx / Wide Field Ophthalmic Photography 8-bit Image Storage / Transfer
1.2.840.10008.5.1.4.1.1.yyyy / Wide Field Ophthalmic Photography 16-bit Image Storage / Transfer
… / … / …
Changes to NEMA Standards Publication PS 3.3-2013
Digital Imaging and Communications in Medicine (DICOM)
Part 3: Information Object DefinitionsPart 3 Additions
Modify PS3.3 Table A.1-1 to add new IODs for: Wide Field Ophthalmic Photography Imaging (8 and 16 bit)
IODsModules / … / Wide Field
Oph
8-bit / Wide Field
Oph
16-bit / …
Patient / M / M
Clinical Trial Subject / U / U
General Study / M / M
Patient Study / U / U
Clinical Trial Study / U / U
General Series / M / M
Ophthalmic Series / M / M
Clinical Trial Series / U / U
…
Synchronization / M / M
…
General Equipment / M / M
Enhanced General Equipment / M / M
SC Equipment
General Image / M / M
Image Plane
Image Pixel / M / M
Enhanced Contrast/Bolus / C / C
…
Cine / C / C
Multi-frame / M / M
…
Ophthalmic Photography Image / M / M
Wide Field Ophthalmic Photography Image / M / M
Wide Field Ophthalmic Photography Quality Rating / C / C
Ocular Region Imaged / M / M
Ophthalmic Photography Acquisition Parameters / M / M
Ophthalmic Photographic Parameters / M / M
SOP Common / M / M
Modify PS3.3 Annex A
A.xx Wide Field Ophthalmic Photography 8-bit Image Information Object Definition
This Section defines an Information Object to be used with several types of ophthalmic photographic imaging devices that generate wide field OP 8-bit images, including fundus cameras, slit lamp cameras, scanning laser ophthalmoscopes, stereoscopic cameras, video equipment and digital photographic equipment.
A.xx.1 Wide Field Ophthalmic Photography Image IOD Description
The Wide Field Ophthalmic Photography 8-bit Image IOD specifies a single-frame or a multi-frame image acquired on a digital photographic DICOM modality. This IOD can be used to encode single wide Field ophthalmic images and other combinations including cine sequences.
A.xx.2 Wide Field Ophthalmic Photography Image IOD Entity-Relationship Model
The E-R Model in Section A.1.2 of this Part depicts those components of the DICOM Information Model that directly reference the Wide Field Ophthalmic Photography 8-bit IOD, with exception of the Curve, VOI LUT, Frame of Reference and Modality LUT entities, which are not used. Table A.xx-1 specifies the Modules of the Wide Field Ophthalmic Photography 8-bit Image IOD.
A.xx.3 Wide Field Ophthalmic Photography Image IOD Modules
Table A.xx-1
WIDE FIELD OPHTHALMIC PHOTOGRAPHY 8-bit IMAGE IOD MODULES
Patient / Patient / C.7.1.1 / M
Clinical Trial Subject / C.7.1.3 / U
Study / General Study / C.7.2.1 / M
Patient Study / C.7.2.2 / U
Clinical Trial Study / C.7.2.3 / U
Series / General Series / C.7.3.1 / M
Ophthalmic Photography Series / C.8.17.1 / M
Clinical Trial Series / C.7.3.2 / U
Frame of Reference / Synchronization / C.7.4.2 / M
Equipment / General Equipment / C.7.5.1 / M
Image / General Image / C.7.6.1 / M
Image Pixel / C.7.6.3 / M
Enhanced Contrast/Bolus / C 7.6.4.b / C – Required if contrast was administered; see A.42.4.2
Cine / C.7.6.5 / C - Required if there is a sequential temporal relationship between all frames
Multi-frame / C.7.6.6 / M
Ophthalmic Photography Image / C.8.17.2 / M
Wide Field Ophthalmic Photography Image / C.8.17.x / M
Wide Field Ophthalmic Photography Quality Rating / C.8.17.y / C – Required if a quality rating value exists for the this SOP Instance
Ocular Region Imaged / C.8.17.5 / M
Ophthalmic Photography Acquisition Parameters / C.8.17.4 / M
Ophthalmic Photographic Parameters / C.8.17.3 / M
SOP Common / C.12.1 / M
A.xx.4 Wide Field Ophthalmic Photography Image IOD Content Constraints
The following constraints on Series and Image attributes take precedence over the descriptions given in the Module Attribute Tables.
A.xx.4.1 Bits Allocated, Bits Stored, and High Bit
For Wide Field Ophthalmic Photography 8 bit images, the Enumerated Value of Bits Allocated (0028,0100) (Image Pixel Module, C.7.6.3) shall be 8; the Enumerated Value of Bits Stored (0028,0101) shall be 8; and the Enumerated Value of High Bit (0028,0102) shall be 7.
For Wide Field Ophthalmic Photography 16 bit images, the Enumerated Value of Bits Allocated (0028,0100) (Image Pixel Module, C.7.6.3) shall be 16; the Enumerated Value of Bits Stored (0028,0101) shall be 16; and the Enumerated Value of High Bit (0028,0102) shall be 15.
A.xx.4.2 Contrast/Bolus Agent Sequence
For Contrast/Bolus Agent Sequence (0018,0012), the defined CID 4200 shall be used.
A.yy Wide Field Ophthalmic Photography 16-bit Image Information Object Definition
This Section defines an Information Object to be used with several types of ophthalmic photographic imaging devices that generate wide field OP 16-bit images, including fundus cameras, slit lamp cameras, scanning laser ophthalmoscopes, stereoscopic cameras, video equipment and digital photographic equipment.
A.yy.1 Wide Field Ophthalmic Photography Image IOD Description
The Wide Field Ophthalmic Photography 16-bit Image IOD specifies a single-frame or a multi-frame image acquired on a digital photographic DICOM modality. This IOD can be used to encode single wide Field ophthalmic images and other combinations including cine sequences.
A.yy.2 Wide Field Ophthalmic Photography Image IOD Entity-Relationship Model
The E-R Model in Section A.1.2 of this Part depicts those components of the DICOM Information Model that directly reference the Wide Field Ophthalmic Photography 16-bit IOD, with exception of the Curve, VOI LUT, Frame of Reference and Modality LUT entities, which are not used. Table A.xx-1 specifies the Modules of the Wide Field Ophthalmic Photography 16-bit Image IOD.
A.yy.3 Wide Field Ophthalmic Photography Image IOD Modules
Table A.yy-1
WIDE FIELD OPHTHALMIC PHOTOGRAPHY 16-bit IMAGE IOD MODULES
Patient / Patient / C.7.1.1 / M
Clinical Trial Subject / C.7.1.3 / U
Study / General Study / C.7.2.1 / M
Patient Study / C.7.2.2 / U
Clinical Trial Study / C.7.2.3 / U
Series / General Series / C.7.3.1 / M
Ophthalmic Photography Series / C.8.17.1 / M
Clinical Trial Series / C.7.3.2 / U
Frame of Reference / Synchronization / C.7.4.2 / M
Equipment / General Equipment / C.7.5.1 / M
Image / General Image / C.7.6.1 / M
Image Pixel / C.7.6.3 / M
Enhanced Contrast/Bolus / C 7.6.4.b / C – Required if contrast was administered; see A.42.4.2
Cine / C.7.6.5 / C - Required if there is a sequential temporal relationship between all frames
Multi-frame / C.7.6.6 / M
Ophthalmic Photography Image / C.8.17.2 / M
Wide Field Ophthalmic Photography Image / C.8.17.x / M
Wide Field Ophthalmic Photography Quality Rating / C.8.17.y / C – Required if a quality rating value exists for the this SOP Instance
Ocular Region Imaged / C.8.17.5 / M
Ophthalmic Photography Acquisition Parameters / C.8.17.4 / M
Ophthalmic Photographic Parameters / C.8.17.3 / M
SOP Common / C.12.1 / M
A.yy.4 Wide Field Ophthalmic Photography Image IOD Content Constraints
The following constraints on Series and Image attributes take precedence over the descriptions given in the Module Attribute Tables.
A.yy.4.1 Bits Allocated, Bits Stored, and High Bit
For Wide Field Ophthalmic Photography 16 bit images, the Enumerated Value of Bits Allocated (0028,0100) (Image Pixel Module, C.7.6.3) shall be 16; the Enumerated Value of Bits Stored (0028,0101) shall be 16; and the Enumerated Value of High Bit (0028,0102) shall be 15.
A.yy.4.2 Contrast/Bolus Agent Sequence
For Contrast/Bolus Agent Sequence (0018,0012), the defined CID 4200 shall be used.
Modify PS3.3 Annex C
C.8.17.X Wide Field Photography Ophthalmic Coordination Containers Image Module
Table C.8.17.X-1 specifies the Attributes that describe an extension to the Ophthalmic Image module for wide field ophthalmic images using the three coordination containers method.
Table C.8.17.X-1
WIDE FIELD OPHTHALMIC PHOTOGRAPHY IMAGE MODULE ATTRIBUTES
Projection Method Code Sequence / (00gg,0012) / 1 / The projection method used to project the 2D Pixel Image data (0028,0100) to the 3D Cartesian coordinates (3CC) in the Coordinates Container Sequence (00gg,0018).
Only a single Item shall be permitted in this sequence.
>Include 'Code Sequence Macro' Table 8.8-1. Defined Context ID is 42x1
Projection Method Algorithm Sequence / (00gg,0013) / 1 / Software algorithm used to provide projection method.
Only a single Item shall be permitted in this sequence.
>Include ‘Algorithm Identification Macro’ Table 10-19
Include ‘General Anatomy Mandatory Macro’ Table 10-5 / The concept code for Anatomic Region Sequence (0008,2218) shall be (T-AA000, SRT, “Eye”), and Defined Context ID 244 shall be used for Anatomic Region Modifier Sequence (0008,2220).
Only a single Item shall be permitted in this sequence.
Estimated Ophthalmic Axial Length / (00gg,0015) / 1C / The estimated axial length measurement, in mm.
Required if Ophthalmic Axial Length (0022,1019) is not present
Ophthalmic Axial Length / (0022,1019) / 1C / The actual axial length measurement, in mm.
Required if Estimated Ophthalmic Axial Length (00gg,0015) is not present.
Image Type / (0008,0008) / 1 / Image identification characteristics.
See C.8.X.2.1.1 for specialization.
Ophthalmic FOV Field / (00gg,0017) / 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 equal the radius).
Coordinates Container Sequence / (00gg,0018) / 1 / Three coordinate containers (3CC) includes 3D coordinate of all or a subset of pixels (namely coordinate points) to the 2D image. If the number of coordinate points is less than the number of image pixels, the 3D coordinate of every pixel is then computed by using Interpolation Type (0052,0039) from the coordinate of the coordinate points.
One or more Items are permitted in this sequence.
Interpolation Type / (0052,0039) / 1 / The type of interpolation used for computing the Cartesian coordinate of every pixel from the coordinate of the set of Coordinates Point Location (00gg,0020).
Enumerated Value:
SPLINE
NONE
>Rows / (0028,0010) / 1 / Number of rows in the image to convey the coordinate point locations for this item.
>Column / (0028,0011) / 1 / Number of columns in the image to convey the coordinate point locations for the item.
>Referenced Frame Numbers / (0040,A136) / 1C / 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.
Required if the values in this sequence item do not apply to all frames.
Coordinates Container Point Location Sequence / (00gg,0019) / 1 / The container to convey the specific point location (3D coordinate) for each pixel in the image or a subset of the image pixels when interpolation is used.
One or more Items are permitted in this sequence.
Coordinates Point Location / (00gg,0020) / 1 / The x, y, and z coordinate of a point in the image, in mm.
The origin of these points shall be the center of the pupil (i.e. the x, y and z coordinates of 0.0, 0.0, 0.0, in mm). See C.8.x.2.1.2 for further explanation.
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.
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”). Shall not be sent when Coordinates Container Sequence ((00gg,0018) or Anatomic Structure Reference Point (0022,1463) is present.
May be present otherwise.
C.8.17.x.1 Wide Field Ophthalmic Photography Image Attribute Descriptions
C.8.17.x.1.1 Image TypeCoordinates Points Location
For Wide Field Ophthalmic Photography Images, Image Type (0008,0008) is specified to be Type 1 and Value 3 shall only be present if Value 1 is DERIVED;
Defined Terms for Value 3:
MONTAGE