In plain words: Small structures in medical scans get ignored because standard training judges the whole image at once. Feeding both the full scan and its region of interest to the loss and the checker improved segmentation scores over baseline methods on two imbalanced datasets.
Abstract
Automated medical image segmentation is an important step in many medical procedures. Recently, deep learning networks have been widely used for various medical image segmentation tasks, with U-Net and generative adversarial nets (GANs) being some of the commonly used ones. Foreground-background class imbalance is a common occurrence in medical images, and U-Net has difficulty in handling class imbalance because of its cross entropy (CE) objective function. Similarly, GAN also suffers from class imbalance because the discriminator looks at the entire image to classify it as real or fake. Since the discriminator is essentially a deep learning classifier, it is incapable of correctly identifying minor changes in small structures. To address these issues, we propose a novel context based CE loss function for U-Net, and a novel architecture Seg-GLGAN. The context based CE is a linear combination of CE obtained over the entire image and its region of interest (ROI). In Seg-GLGAN, we introduce a novel context discriminator to which the entire image and its ROI are fed as input, thus enforcing local context. We conduct extensive experiments using two challenging unbalanced datasets: PROMISE12 and ACDC. We observe that segmentation results obtained from our methods give better segmentation metrics as compared to various baseline methods.
Balamurali Murugesan, Kaushik Sarveswaran, Vijaya Raghavan S, Sharath M Shankaranarayana, Keerthi Ram, Mohanasankar Sivaprakasam
arXiv:2001.02387 · eess.IV, cs.CV · submitted Jan 8, 2020
abstract · pdf · html · Accepted in ISBI 2020