Multimodality analysis of Hyper-reflective Foci and Hard Exudates in Patients with Diabetic Retinopathy

Abstract

To investigate the correlations between hyper-reflective foci and hard exudates in patients with non-proliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR) by spectral-domain optical coherence tomography (SD OCT) images. Hyper-reflective foci in retinal SD OCT images were automatically detected by the developed algorithm. Then, the cropped CFP images generated by the semi-automatic registration method were automatically segmented for the hard exudates and corrected by the experienced clinical ophthalmologist. Finally, a set of 5 quantitative imaging features were automatically extracted from SD OCT images, which were used for investigating the correlations of hyper-reflective foci and hard exudates and predicting the severity of diabetic retinopathy. Experimental results demonstrated the positive correlations in area and amount between hard exudates and hyper-reflective foci at different stages of diabetic retinopathy, with statistical significance (all p < 0.05). In addition, the area and amount can be taken as potential discriminant indicators of the severity of diabetic retinopathy.

Figure 1

Diagram showing the processing pipeline of our multimodality analysis method.

Figure 2

Registration of CFP and SD OCT en face image. (A) Original CFP image. (B) SD OCT en face image generated by projecting a region between the IS/OS and BM boundaries, where the en face image can better highlight blood vessels. (C) SD OCT en face image is superposed on the CFP image. (D) The cropped CFP image.

Figure 3

Example of hard exudates segmentation. (A) The cropped CFP image. (B) Automatic segmentation is superposed on the cropped CFP image, where the white line represents the outline of the hard exudates. (C) The corrected segmentation of hard exudates.

Figure 4

Hyper-reflective foci segmentation, (A) Hyper-reflective foci 3D surface view, where green and pink represent the fitted IS surface and the detected hyper-reflective foci, respectively. (B) Results from hyper-reflective foci segmentation in an example of a B-scan, corresponding to the yellow line in (A). (C) Generated hyper-reflective foci topographic height map and (D) Topographic height map segmentation.

Figure 5

Results of agreement evaluation for hard exudates between CFP and SD OCT. Correlations between HE areas measured by SD OCT and CFP at NPDR and PDR are displayed as (A) and (B), respectively.

Figure 6

The combined analysis of SD OCT B-scan and aligned CFP. (A) The cropped CFP images, where hyper-reflective regions represent hard exudates. (B) The comparison of HE segmentation results on CFP and hyper-reflective foci results on SD OCT. The black regions are hard exudates measured by CFP and SD OCT. The green regions measured by CFP are hard exudates that are missed by SD OCT. The red regions represent hyper-reflective foci on SD OCT, where these foci could not be identified in the corresponding CFP. (C) and (D) SD OCT B-scan images correspond to the white and yellow dotted line, respectively, where the pink regions and the white regions are hyper-reflective foci and hard exudates, respectively.

Figure 7

Results of the reflectivity and altitude distribution in SD OCT. (A) Reflectivity assessment of hyper-reflective foci and hard exudate in patients with NPDR and PDR. (B) Results of the altitude distribution of hyper-reflective foci and hard exudate in patients with NPDR and PDR.

Figure 8

(A) Area assessment of hard exudate and hyper-reflective foci (including hard exudates) in patients with NPDR and PDR on SD OCT, (B) Results from the amount assessment of hard exudate and hyper-reflective foci (including hard exudates) in patients with NPDR and PDR on SD OCT. (C) Average distance to macular fovea for hard exudate and hyper-reflective (including hard exudates) in patients with NPDR and PDR.

Figure 9

Results of analysis of the difference. (A) Results of the difference in hard exudates between NPDR and PDR in SD OCT. (B) Results of the difference in hyper-reflective foci (excluding hard exudates) between NPDR and PDR in SD OCT.