Dr Jano van Hemert, FRSE

Science, software and scripts

Wide Field Ophthalmic Photography Image Storage SOP Classes; DICOM Supplement 173

29 Mar 2015

With a small team comprising members from different companies and representatives of the American Academy of Ophthalmology, a new supplement was delivered from conception to approval in 14 months.

Supplement 173 defines Storage SOP Classes to enable anatomically correct measurements on wide field ophthalmic photography images.
Vendors have implemented new technology that enables the acquisition of OP images using wide field fundus photography. The Ophthalmic Photography IOD does not address wide fields, varied pixel spacing, and proper measurement of a stereographic projection or other methods of projection/mapping. Since the back of the eye is approximately a concave sphere, taking a very wide field image of it introduces large errors 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 two new Information Object Definitions (IODs) are necessary to adequately represent wide field fundus photography.

Manufacturers of ophthalmic photographic imaging devices have been developing OP images (using a narrow field) for many years in DICOM (i.e., these SOP Classes are widely supported by the DICOM ophthalmic community). Therefore, the wide field OP image storage SOP Classes are an extension to already existing narrow field DICOM SOP Classes.

Supplement 173 PDF