Zeiss CIRRUS HD-OCT 500, Руководство пользователя

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CIRRUS HD-OCT User Manual 2660021169012 Rev. A 2017-12
Criteria for Image Acceptance
7-7
CIRRUS OCT Angiography Acceptance Criteria
When reviewing CIRRUS OCT Angiography Scans for acceptability, the following should be
considered:
• Signal Quality
• Decorrelation Tails
• Segmentation Errors
Each of these is discussed in the sections which follow.
Signal Quality
CIRRUS OCT Angiography is more sensitive to signal quality than structural OCT imaging.
The best CIRRUS OCT Angiography images are obtained when the signal strength is 8 or
better. A low signal strength may lead to dark areas on the scan and poor quality scans,
which can affect interpretation of the images.
Figure 7-5 shows an example of an image
with poor signal quality throughout the image. In these cases, the B-scan usually looks
dark or blurry as well.
Because of this sensitivity, CIRRUS OCT Angiography can occasionally show dark spots that
are not a result of capillary dropout but rather due to poor local signal as shown in
Figure
7-5 A . This can occur due to floaters or other media opacities. One way to confirm that an
opacity is the source of the dark spot is to compare the angiography
en face
to the
structural
en face
image Figure 7-5 B . Another method is to examine the B-scan Figure
7-5 C . In real disease, the CIRRUS OCT Angiography image will appear dark, but the B-scan
and the structural
en face
image will not. Taking more than one scan may help in cases
with floaters. If a dark area is in a different location between different scans, then it is a
floater.