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2016
2016
Supplement 197: OCT Angiography Image Storage SOP Classes DICOM WG9 - - PowerPoint PPT Presentation
Supplement 197: OCT Angiography Image Storage SOP Classes DICOM WG9 - - PowerPoint PPT Presentation
Supplement 197: OCT Angiography Image Storage SOP Classes DICOM WG9 Eye Care 2016 OCT-A Separating Vascular Networks 2016 OCT-Angiography - Outcome Clinicians typically make their assessment based on the OCT En face images derived from OCT
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2016
OCT-Angiography - Outcome
Clinicians typically make their assessment based on the OCT En face images derived from OCT structure and/or flow volumetric data.
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2016
OCT-A
- Separating Vascular Networks
- Fluorescence angiography – typically using
fluorescein (FA) or indocyanine green (ICG) as the fluorescent contrast agent – has been the standard method, but both have disadvantages:
- nausea and allergic reactions
- patients have to be prepared before the procedure,
monitored afterwards, and the contrast agent isn’t free
- f charge
- OCT-A will not replace the above for all cases – e.g.
it’s not able to capture leakages
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2016
OCT-A
Patient with mCNV. FA/ICGA images (top) show capillary leakage; OCT-A (bottom) provides a superior visualization of the newly formed vessels and depth-resolved resolution of vascular perfusion – neovascularization is clearly visible in deeper layers (right) than in superficial layers (left).
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2016
Vascular Network of the Posterior Segment
- Superficial Vascular Plexus (SP)
- Large Vessels
- Observable with
- phthalmoscope
- Deep Vascular Plexus (DP)
- Fine network of small sized
capillaries
- Choroid
- Choroiocapillaris
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2016
Layers of the Vascular Network
Perifoveal Arcade Retinal Nerve Fiber Layer
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Superficial Capillary Plexus & Perifoveal Arcade Ganglion Cell Layer
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Superficial Capillary Plexus (& Perifoveal Arcade) Inner Plexiform Layer
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Deep Capillary Plexus Inner Nuclear Layer
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Deep Capillary Plexus Outer Plexiform Layer
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2016
Avascular Layer & copy of superficial vascular plexus Bruch’s Membrane - RPE
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Choriocapillaris 5µm distance (BM) 5µm thickness
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Sattler’s Layer 20µm distance (BM) 10µm thickness
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Haller’s Layer 40µm distance (BM) 15µm thickness
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2016
HOW DOES OCT-A WORK IN PRINCIPLE?
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2016
OCT-Angiography
A sequence of B-scans is acquired at a fixed retinal location. Changes in OCT images reflect blood flow.
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OCT-Angiography
Segmentation of retinal layers to define OCT slab. Summation of flow signal within an OCT slab, multiple frames are acquired at each B-scan location OCT angiography B-scan
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Image Process Performed to Generate En face Images
Structural Volume Flow Volume En Face Raw multiple B-Scans
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2016
OCT-A
- Stage 1 – OCT “raw data” acquires volumetric data set of
mulitple B-scans in a proprietary format (may be stored using DICOM Raw Data SOP Class)
- Stage 2 – OCT “raw data” analyzed to derive two DICOM
standard volumetric SOP Instances
- Structural OCT image stored in the OPT SOP Class
(OCT surface segmentation included)
- Differences in signal between B-scans produces OCT angiographic
flow volume information (stored in the newly defined Ophthalmic Tomography Angiographic Adjunctive Image Storage SOP Class)
- Stage 3 – Analysis of the above two SOP Instances enables
generation of multiple en face images showing structural and/or angiographic flow images (stored in the newly defined En face Image Storage SOP Class)
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Relationships Between DICOM OCT-A Based SOP Instances
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2016
En Face Image
- OCT angiography provides information about the
vascular flow
- Layers of the vascular architecture can be separated
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2016