A Modified U-Net Convolutional Network Featuring a Nearest-neighbor Re-sampling-based Elastic-Transformation for Brain Tissue Characterization and Segmentation.

The detection and segmentation of brain tumors from Magnetic Resonance Imaging (MRI) is a very challenging task, despite the availability of modern medical image processing tools. Neuro-radiologists still diagnose deadly brain cancers such as even glioblastoma using manual segmentation. This approach is not only tedious, but also highly variable, featuring limited accuracy and precision, and hence raising the need for more robust, automated techniques. Deep learning methods such as the U-Net deep convolutional neural networks have been widely used in biomedical image segmentation. Although this model was demonstrated to yield desirable results on the BRATS 2015 dataset by using a pixel-wise segmentation map of the input image as an auto-encoder, which assures best segmentation accuracy, the output only showed limited accuracy and robustness for a number of cases. The goal of this work was to improve the U-net model by replacing the de-convolution component with an up-sampled by the Nearest-neighbor algorithm and also employing an elastic transformation to augment the training dataset to render the model more robust, especially for the segmentation of low-grade tumors. The proposed Nearest-Neighbor Re-sampling Based Elastic-Transformed (NNRET) U-net Deep CNN framework has been trained on 285 glioma patients BRATS 2017 MR dataset available through the MICCAI 2017 grand challenge. The framework has been tested on 146 patients using Dice similarity coefficient (DSC) & Intersection over Union (IoU) performance metrics and outweighed the classic U-net model.