Anatomy-Aware Siamese Network: Exploiting Semantic Asymmetry for Accurate Pelvic Fracture Detection in X-ray Images

TL;DR

This paper introduces a novel Siamese network with spatial transformer and contrastive learning for pelvic fracture detection in X-ray images, leveraging anatomical symmetry analysis to improve accuracy in emergency diagnosis.

Contribution

It presents a new anatomy-aware Siamese network framework that effectively models semantic symmetry and asymmetry for more accurate pelvic fracture detection in X-ray images.

Findings

Achieved an AUC of 0.9771, outperforming existing methods.

Utilized the largest dataset of 2,359 pelvic X-rays for evaluation.

Demonstrated improved clinical diagnostic indications.

Abstract

Visual cues of enforcing bilaterally symmetric anatomies as normal findings are widely used in clinical practice to disambiguate subtle abnormalities from medical images. So far, inadequate research attention has been received on effectively emulating this practice in CAD methods. In this work, we exploit semantic anatomical symmetry or asymmetry analysis in a complex CAD scenario, i.e., anterior pelvic fracture detection in trauma PXRs, where semantically pathological (refer to as fracture) and non-pathological (e.g., pose) asymmetries both occur. Visually subtle yet pathologically critical fracture sites can be missed even by experienced clinicians, when limited diagnosis time is permitted in emergency care. We propose a novel fracture detection framework that builds upon a Siamese network enhanced with a spatial transformer layer to holistically analyze symmetric image features. Image features are spatially formatted to encode bilaterally symmetric anatomies. A new contrastive feature learning component in our Siamese network is designed to optimize the deep image features being more salient corresponding to the underlying semantic asymmetries (caused by pelvic fracture occurrences). Our proposed method have been extensively evaluated on 2,359 PXRs from unique patients (the largest study to-date), and report an area under ROC curve score of 0.9771. This is the highest among state-of-the-art fracture detection methods, with improved clinical indications.