Ensemble of multi-stage deep convolutional neural networks for automated grading of diabetic retinopathy using image patches

Abstract

Diabetic retinopathy (DR) is one of the most common retinal diseases that cause preventable blindness in diabetic patients. The timely screening and grading of retinal images minimize the possibility of vision loss. However, manual screening of retinal images, for detecting micro lesions in the early stages of DR, is time-consuming. This paper proposes an ensemble of deep convolutional neural network (CNN) models for accurate detection and grading of DR using fundus images. Each input image is divided into four patches at the first stage and passed on to pre-trained CNN models (InceptionV3, Xception) for training. The relevant features in the shallow-dense layers of CNN models are utilized as prior knowledge. The integration of shallow and dense layer features helps the model learn the significant information of DR images. At the second stage, a classifier based on artificial neural network is trained using the fused probability vectors of four patches. The results of individual CNN models are combined to generate the final decision in the third stage. This ensemble approach of multi-stage deep learning model improves the overall classification accuracy of diabetic retinopathy grading. Among the five different classification schemes presented in this paper, multistage patch-based deep CNN (MPDCNN), in which local patch-based and holistic details of fundus image are concatenated, provides the best classification accuracy. This ensemble classifier exhibits 96.2 % classification accuracy with fivefold cross-validation.

Keywords

• Diabetic retinopathy
• Image patches
• Ensemble
• Shallow and dense layer features
• Pre-trained CNN models