FocusNetv2: Imbalanced Large and Small Organ Segmentation with Adversarial Shape Constraint for Head and Neck CT Images

TL;DR

FocusNetv2 is a two-stage deep learning framework designed to accurately segment both large and small organs in head and neck CT images, employing an adversarial shape constraint to improve small organ delineation.

Contribution

This paper introduces FocusNetv2, a novel two-stage neural network with specialized sub-networks for small organ localization and segmentation, incorporating an adversarial shape constraint for improved accuracy.

Findings

Outperforms state-of-the-art methods on self-collected dataset

Achieves superior segmentation accuracy on MICCAI 2015 dataset

Effectively handles imbalanced organ sizes in CT images

Abstract

Radiotherapy is a treatment where radiation is used to eliminate cancer cells. The delineation of organs-at-risk (OARs) is a vital step in radiotherapy treatment planning to avoid damage to healthy organs. For nasopharyngeal cancer, more than 20 OARs are needed to be precisely segmented in advance. The challenge of this task lies in complex anatomical structure, low-contrast organ contours, and the extremely imbalanced size between large and small organs. Common segmentation methods that treat them equally would generally lead to inaccurate small-organ labeling. We propose a novel two-stage deep neural network, FocusNetv2, to solve this challenging problem by automatically locating, ROI-pooling, and segmenting small organs with specifically designed small-organ localization and segmentation sub-networks while maintaining the accuracy of large organ segmentation. In addition to our original FocusNet, we employ a novel adversarial shape constraint on small organs to ensure the consistency between estimated small-organ shapes and organ shape prior knowledge. Our proposed framework is extensively tested on both self-collected dataset of 1,164 CT scans and the MICCAI Head and Neck Auto Segmentation Challenge 2015 dataset, which shows superior performance compared with state-of-the-art head and neck OAR segmentation methods.