Материал: part17

UUU.1.3.4 Transformation Method Code Sequence​

If Transformation Method Code Sequence (0022,1512) is (111791, DCM, "Spherical projection") is used then all coordinates in the​ Two Dimensional to Three Dimensional Map Sequence (0022,1518) are expected to lie on a sphere with a diameter that is equal to​ Ophthalmic Axial Length (0022,1019).​

The use of this model for representing the 3D retina enables the calculation of the shortest distance between two points using great​ circles as per section UUU.1.3.2.​

UUU.2 Relationship Between Ophthalmic Tomography Image and Ophthalmic​ Optical Coherence Tomography B-scan Volume Analysis IODs​

This Section provides examples of the relationship between the Ophthalmic Tomography Image SOP Instance(s) and Ophthalmic​ Optical Coherence Tomography B-scan Volume Analysis SOP Instance(s).​

Below is a typical example.​

•​Ophthalmic Tomography Image SOP Instance UID is "1.2.3.4.5" and contains five frames.​

•​Ophthalmic Optical Coherence Tomography B-scan Volume Analysis SOP Instance encodes five frames (e.g., one frame for each​ ophthalmic tomography frame).​

•​References are encoded via the Per-frame Functional Groups Sequence (5200,9230) using Attributes Derivation Image Sequence​ (0008,9124) and Source Image Sequence (0008,2112).​

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FigureUUU.2-1.OphthalmicTomographyImageandOphthalmicOpticalCoherenceTomographyB-scan​

Volume Analysis IOD Relationship - Simple Example​

Below is a more complex example.​

•​Ophthalmic TomographyImage SOP Instance UID is "2.3.4.5" and contains 3 frames.​

•​Ophthalmic TomographyImage SOP Instance UID is "1.6.7.8.9" and contains 2 frames.​

•​Ophthalmic Optical Coherence Tomography B-scan Volume Analysis SOP Instance encodes five frames (e.g., one frame for each​ Ophthalmic TomographyFrame from the two Ophthalmic Tomography Image SOP Instances).​

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FigureUUU.2-2.OphthalmicTomographyImageandOphthalmicOpticalCoherenceTomographyB-scan​

Volume Analysis IOD Relationship - Complex Example​

UUU.3 Ophthalmic Tomography Angiography Examples​

OCT en face images are derived from images obtained using OCT technology (i.e., structural OCT volume images plus angiographic​ flow volume information). With special image acquisition sequences and post hoc image processing algorithms, OCT-A detects the​ motion of the blood cells in the vessels to produce images of retinal and choroidal blood flow with capillary level resolution. En face​ images derived from these motion contrast volumes are similar to images obtained in retinal fluorescein angiography with contrast​ dye administered intravenously, though differences are observed when comparing these two modalities. This technology enables a​ high resolution visualization of the retinal and choroidal capillary network to detect the growth of abnormal blood vessels to provide​ additional insights in diagnosing and managing a variety of retinal diseases including diabetic retinopathy, neovascular age-related​ macular degeneration, retinal vein occlusion and others.​

The following are examples of how the ophthalmic tomography angiography DICOM objects may be used.​

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UUU.3.1 Clinical Examples​

UUU.3.1.1 Diabetic Macular Ischemia​

A 54 year old female patient with an 18 year history of DM2 presents with unexplained painless decreased visual acuity in both eyes.​ The patient was on hemodialysis (HD) for diabetes related renal failure. She had a failed HD shunt in the right arm and a functioning​ shunt in the left. SD-OCT testing showed no thickening of the macula. Because of her renal failure and HD history IVFA was deferred​ andOCTangiographyofthemaculaewasperformed.Thisshowedsignificantwideningofthefovealavascularzone(FAZ)explaining​ her poor visual acuity and excluding treatment opportunities.​

Figure UUU.3.1-1. Diabetic Macular Ischemia example​

UUU.3.1.2 Age Related Macular Degeneration​

A 71 Year Old Male Patient Presents With A 3 Month History of Decreased Visual Acuity and Distorted Vision in The Right Eye. He​ Demonstrates A Well-defined Elevation of The Deep Retina Adjacent to The Fovea Od by Biomicroscopy That Correlates to A Small​ Pigment Epithelial Detachment (ped) Shown by Sd-oct. OCT Angiography Demonstrated A Subretinal Neovascular Network in The​ Same Area. This Was Treated With Intravitreal Anti-vegf Injection Monthly For Three Months With Resolution of The Ped and Incre-​ mentalRegressionofTheSubretinalNeovascularMembranebyPointtoPointRegistrationOCTAngiographyandFinallyNon-perfusion​ of The Previous Srn.​

Figure UUU.3.1-2. Age related Macular Degeneration example​

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UUU.3.1.3 Branch Retinal Vein Occlusion​

A 59 y/o male patient with hypertension and long smoking history presents with a six week history of painless decrease in vision in​ therighteye.Ophthalmoscopyshoweddilatedandtortuousveinsinferiortemporallyintherighteyewithasuperiortemporaldistribution​ of deep retinal hemorrhages that extended to the mid-periphery, but did not include the macula. SD-OCT showed thickening of the​ macula and OCT angiography showed rarefaction of the retinal capillaries consistent with ischemic branch retinal vein occlusion and​ macular edema.​

Figure UUU.3.1-3. Branch Retinal Vein Occlusion example​

UUU.3.2 Research Examples​

UUU.3.2.1 Proliferative Diabetic Retinopathy​

A38-year-oldmalepatientwith26yearhistoryoftype1diabetesexaminedforevaluationof10-dayhistoryofscantvitreoushemorrhage​ due to neovascularization of the optic disc.​

Figure UUU.3.2-1. Proliferative Diabetic Retinopathy example​

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