Fully automatic segmentation and objective assessment of atrial scars for long-standing persistent atrial fibrillation patients using late gadolinium-enhanced MRI.

Guang Yang,Shouvik Haldar,Lei Li,Jennifer Keegan,Habib Khan,Xujiong Ye,Eva Nyktari,David Firmin,Raad Mohiaddin,Greg Slabaugh,Ricardo Wage,Tom Wong,Xiahai Zhuang

doi:10.1002/mp.12832

Abstract

PurposeAtrial fibrillation (AF) is the most common heart rhythm disorder and causes considerable morbidity and mortality, resulting in a large public health burden that is increasing as the population ages. It is associated with atrial fibrosis, the amount and distribution of which can be used to stratify patients and to guide subsequent electrophysiology ablation treatment. Atrial fibrosis may be assessed noninvasively using late gadolinium‐enhanced (LGE) magnetic resonance imaging (MRI) where scar tissue is visualized as a region of signal enhancement. However, manual segmentation of the heart chambers and of the atrial scar tissue is time consuming and subject to interoperator variability, particularly as image quality in AF is often poor. In this study, we propose a novel fully automatic pipeline to achieve accurate and objective segmentation of the heart (from MRI Roadmap data) and of scar tissue within the heart (from LGE MRI data) acquired in patients with AF.MethodsOur fully automatic pipeline uniquely combines: (a) a multiatlas‐based whole heart segmentation (MA‐WHS) to determine the cardiac anatomy from an MRI Roadmap acquisition which is then mapped to LGE MRI, and (b) a super‐pixel and supervised learning based approach to delineate the distribution and extent of atrial scarring in LGE MRI. We compared the accuracy of the automatic analysis to manual ground truth segmentations in 37 patients with persistent long‐standing AF.ResultsBoth our MA‐WHS and atrial scarring segmentations showed accurate delineations of cardiac anatomy (mean Dice = 89%) and atrial scarring (mean Dice = 79%), respectively, compared to the established ground truth from manual segmentation. In addition, compared to the ground truth, we obtained 88% segmentation accuracy, with 90% sensitivity and 79% specificity. Receiver operating characteristic analysis achieved an average area under the curve of 0.91.ConclusionCompared with previously studied methods with manual interventions, our innovative pipeline demonstrated comparable results, but was computed fully automatically. The proposed segmentation methods allow LGE MRI to be used as an objective assessment tool for localization, visualization, and quantitation of atrial scarring and to guide ablation treatment.

Highlights

Atrial fibrillation (AF) is the most common arrhythmia of clinical significance, resulting in a large public health burden that is increasing as the population ages
We propose a novel fully automatic segmentation and objective assessment of atrial scarring for long-standing persistent AF patients scanned by Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI)
We propose to use the spatially encoded mutual information (SEMI) method, which has been shown to be robust against intensity nonuniformity and different intensity contrast,[36] that is ImageSimilarityðI; AaÞ 1⁄4 fS1; . . .; Sns g where fS1; . . .; Sns g are the SEMI and computed based on the spatially encoded joint histogram, FIG. 1. (a) Flowchart of the LA + pulmonary veins (PV) segmentation via multiatlas-based whole heart segmentation (MA-WHS) and its validation. (b) Flowchart of the fully automatic atrial scarring segmentation including atrial scarring ground truth construction, super-pixel and support vector machine (SVM) classification-based segmentation and leave-one-patient-out cross-validation

Summary

Introduction

Atrial fibrillation (AF) is the most common arrhythmia of clinical significance, resulting in a large public health burden that is increasing as the population ages It occurs when chaotic and disorganized electrical activity develops in the atria, causing muscle cells to contract irregularly and rapidly. It is associated with structural remodeling, including fibrotic changes in the left atrium[1] and can cause increased morbidity, especially stroke and heart failure. The success rate for a single catheter ablation procedure is just 30–50% at 5-yr follow-up[3,4] and multiple ablations are frequently required. Accurate knowledge of native and previous ablation scarring could be used to stratify patients and guide ablation treatment, reducing the need for repeat procedures.[5]

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