Optical coherence tomography angiography methods

Abstract

Methods of applying OCT angiography are disclosed. In particular, methods of detecting, visualizing and measuring the extent of retinal neovascularization are disclosed. Further disclosed are methods measuring retinal nonperfusion area and choriocapillaris defect area.

1 . A method of measuring a nonperfusion area, the method comprising:
 receiving a set of cross sectional OCT angiograms;   generating an en face inner retina angiogram or an en face choriocapillaris angiogram;   identifying a set of pixels in the en face inner retina angiogram or the en face choriocapillaris angiogram wherein the pixels have decorrelation values less than a cutoff point, thereby generating a nonperfusion map;   identifying nonperfusion areas with an area below a defined number of pixels;   summing the pixels in the nonperfusion areas, thereby measuring a retinal nonperfusion area.   
     
     
         2 . The method of  claim 1  wherein the cutoff point is 2.33 standard deviations below the mean decorrelation value in the en face inner retina angiogram. 
     
     
         3 . The method of  claim 1  further comprising closing a hole in the inner retina angiogram using morphological operations. 
     
     
         4 . The method of  claim 4  further comprising converting the area to physical dimensions. 
     
     
         5 . A method of indicating retinal neovascularization, the method comprising:
 receiving a set of cross sectional OCT angiograms,   generating an en face inner retina angiogram and an en face vitreous angiogram;   generating a composite en face angiogram by overlaying the en face inner retina angiogram and the en face vitreous angiogram;   wherein the vitreous layer is anterior to an inner limiting membrane and the inner retina is between the inner limiting membrane and an outer boundary of the outer plexiform layer and wherein visualization of blood flow above the inner limiting membrane is an indication of retinal neovascularization.   
     
     
         6 . A method of measuring a retinal neovascularization area and flow index, the method comprising:
 receiving a set of cross sectional OCT angiograms;   generating an en face vitreous angiogram;   applying a filter to the en face vitreous angiogram;   using pattern recognition to identify retinal neovascularization;   identifying a set of pixels in the en face vitreous angiogram wherein the pixels have decorrelation values greater a cutoff point   converting the sum of the set of pixels to physical dimensions, thereby measuring the neovascularization area;   dividing the neovascularization area by the area of the en face vitreous angiogram, thereby determining the RNV flow index.   
     
     
         7 . A system for analyzing OCT angiography data comprising:
 an OCT system configured to acquire an OCT image and OCT angiography images of a sample;   a logic subsystem; and   a data holding subsystem comprising machine-readable instructions stored thereon that are executable by the logic subsystem to perform the steps of any of  claims 1 - 6 .