The WEB Occlusion Scale (WOS) is a standardized angiographic assessment scale for reporting aneurysm occlusion achieved with endosaccular flow disruptors such as the Woven EndoBridgeTM.

It is based on the Modified Raymond-Roy Classification, and can be employed to assess the adequacy of treatment. The grading system has been validated to have a reliable interobserver agreement.

WOS A: complete occlusion without an angiographically visible collection of contrast within the marker recess.

WOS B: complete occlusion with an angiographically visible collection of contrast within the marker recess.

WOS C: residual neck filling is indicated by contrast opacification of the aneurysm neck extending beyond the expected bounds of the marker recess.

WOS D: residual aneurysm filling is indicated by contrast opacification extending beyond the aneurysm neck and into the fundus, either deep to the proximal marker recess or around the periphery of the device.

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