Imaging Research Laboratories, Robarts Research Institute, London, Canada.
Acad Radiol. 2012 Feb;19(2):141-52. doi: 10.1016/j.acra.2011.10.007. Epub 2011 Nov 21.
To improve intra- and interobserver variability and enable the use of functional magnetic resonance imaging (MRI) for multicenter, multiobserver studies, we generated a semiautomated segmentation method for hyperpolarized helium-3 ((3)He) MRI. Therefore the objective of this study was to compare the reproducibility and spatial agreement of manual and semiautomated segmentation of (3)He MRI ventilation defect volume (VDV) and ventilation volume (VV) in subjects with asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF).
The multistep semiautomated segmentation method we developed employed hierarchical K-means clustering to classify (3)He MRI pixel intensity values into five user-determined clusters ranging from signal void to hyperintense. A seeded region-growing algorithm was also used to segment the (1)H MRI thoracic cavity for coregistration to the (3)He cluster-map, generating VDV and VV.
We compared manual segmentation performed by an expert observer and semiautomated measurements of (3)He MRI VDV and observed strong significant correlations between the volumes generated using each method (asthma, n = 5, r = 0.89, P < .0001; COPD, n = 5, r = 0.84, P < .0001; CF, n = 5, r = 0.89, P < .0001). Semiautomated VDV had high interobserver reproducibility (coefficient of variation [CV] = 7%, intraclass correlation coefficient [ICC] = 0.96); intraobserver reproducibility was significantly higher for semiautomated (CV = 5%, ICC = 1.00) compared to manual VDV (CV = 12%, ICC = 0.98). Spatial agreement for VV determined using the Dice coefficient (D) was also high for all disease states (asthma, D = 0.95; COPD, D = 0.88; CF, D = 0.90).
Semiautomated segmentation (3)He MRI provides excellent inter- and intraobserver precision with high spatial and quantitative agreement with manual measurements enabling its use in longitudinal studies.
为了提高磁共振成像（MRI）的观察者内和观察者间的可变性，并使其能够用于多中心、多观察者的研究，我们生成了一种针对超极化氦-3（(3)He）MRI 的半自动分割方法。因此，本研究的目的是比较哮喘、慢性阻塞性肺疾病（COPD）和囊性纤维化（CF）患者的手动和半自动分割(3)He MRI 通气缺陷体积（VDV）和通气体积（VV）的可重复性和空间一致性。
我们开发的多步骤半自动分割方法采用分层 K-均值聚类将(3)He MRI 像素强度值分为五个用户确定的聚类，从信号缺失到超强度。还使用了种子区域生长算法来分割(1)H MRI 胸腔，以便与(3)He 聚类图进行配准，生成 VDV 和 VV。
我们比较了由一位专家观察者进行的手动分割和半自动测量的(3)He MRI VDV，并观察到使用每种方法生成的体积之间存在很强的显著相关性（哮喘，n=5，r=0.89，P<.0001；COPD，n=5，r=0.84，P<.0001；CF，n=5，r=0.89，P<.0001）。半自动 VDV 的观察者间可重复性高（变异系数[CV]=7%，组内相关系数[ICC]=0.96）；与手动 VDV（CV=12%，ICC=0.98）相比，半自动 VDV 的观察者内可重复性显著更高（CV=5%，ICC=1.00）。使用 Dice 系数（D）确定的 VV 的空间一致性在所有疾病状态下也很高（哮喘，D=0.95；COPD，D=0.88；CF，D=0.90）。
半自动分割(3)He MRI 提供了出色的观察者内和观察者间精度，与手动测量具有高度的空间和定量一致性，使其能够用于纵向研究。
