The choroid is an important structure of the eye and choroid thickness distribution estimated from optical coherence tomography (OCT) images plays a vital role in analysis of many retinal diseases. This paper proposes a novel group-wise attention fusion network (referred to as GAF-Net) to segment the choroid layer, which can effectively work for both normal and pathological myopia retina. Currently, most networks perform unified processing of all feature maps in the same layer, which leads to not satisfactory choroid segmentation results. In order to improve this , GAF-Net proposes a group-wise channel module (GCM) and a group-wise spatial module (GSM) to fuse group-wise information. The GCM uses channel information to guide the fusion of group-wise context information, while the GSM uses spatial information to guide the fusion of group-wise context information. Furthermore, we adopt a joint loss to solve the problem of data imbalance and the uneven choroid target area. Experimental evaluations on a dataset composed of 1650 clinically obtained B-scans show that the proposed GAF-Net can achieve a Dice similarity coefficient of 95.21±0.73%.
Change of the thickness and volume of the choroid, which can be observed and quantified from optical coherence tomography (OCT) images, is a feature of many retinal diseases, such as aged-related macular degeneration and myopic maculopathy. In this paper, we make purposeful improvements on the U-net for segmenting the choroid of either normal or pathological myopia retina, obtaining the Bruch’s membrane (BM) and the choroidal-scleral interface (CSI). There are two main improvements to the U-net framework: (1) Adding a refinement residual block (RRB) to the back of each encoder. This strengthens the recognition ability of each stage; (2) The channel attention block (CAB) is integrated with the U-net. This enables high-level semantic information to guide the underlying details and handle the intra-class inconsistency problem. We validated our improved network on a dataset which consists of 952 OCT Bscans obtained from 95 eyes from both normal subjects and patients suffering from pathological myopia. Comparing with manual segmentation, the mean choroid thickness difference is 8μm, and the mean Dice similarity coefficient is 85.0%.