Kaaouana Takoua, Bertrand Anne, Ouamer Fatma, Law-Ye Bruno, Pyatigorskaya Nadya, Bouyahia Ali, Thiery Nathalie, Dufouil Carole, Delmaire Christine, Dormont Didier, de Rochefort Ludovic, Chupin Marie
Sorbonne Univ, UPMC Univ Paris 06, UM 75, ICM, F-75013 Paris, France; Inserm, U1127, ICM, F-75013 Paris, France; CNRS, UMR 7225, ICM, F-75013 Paris, France; ICM, Paris, France; Inria, Aramis project-team, Centre Paris-Rocquencourt, France; CATI, Paris, France.
Sorbonne Univ, UPMC Univ Paris 06, UM 75, ICM, F-75013 Paris, France; Inserm, U1127, ICM, F-75013 Paris, France; CNRS, UMR 7225, ICM, F-75013 Paris, France; ICM, Paris, France; Inria, Aramis project-team, Centre Paris-Rocquencourt, France; Neuroradiology, CHRU Pitié Salpêtrière, Paris, France.
Neuroimage Clin. 2016 Aug 9;15:274-283. doi: 10.1016/j.nicl.2016.08.005. eCollection 2017.
INTRODUCTION/PURPOSE: In vivo detection of cerebral microbleeds (CMBs) from T2* gradient recalled echo (GRE) magnitude image suffers from low specificity, modest inter-rater reproducibility and is biased by its sensitivity to acquisition parameters. New methods were proposed for improving this identification, but they mostly rely on 3D acquisitions, not always feasible in clinical practice. A fast 2D phase processing technique for computing internal field maps (IFM) has been shown to make it possible to characterize CMBs through their magnetic signature in routine clinical setting, based on 2D multi-slice acquisitions. However, its clinical interest for CMBs identification with respect to more common images remained to be assessed. To do so, systematic experiments were undertaken to compare the ratings obtained by trained observers with several image types, T2* magnitude, Susceptibility Weighted Imaging reconstructions (SWI) and IFM built from the same T2*-weighted acquisition.
MATERIALS/METHODS: 15 participants from the MEMENTO multi-center cohort were selected: six subjects with numerous CMBs (20 ± 6 CMBs), five subjects with a few CMBs (2 ± 1 CMBs) and four subjects without CMB. 2D multi-slice T2* GRE sequences were acquired on Philips and Siemens 3T systems. After pilot experiments, T2* magnitude, Susceptibility Weighted Imaging (SWI) minimum intensity projection (mIP) on three slices and IFM were considered for the rating experiments. A graphical user interface (GUI) was designed in order to consistently display images in random order. Six raters of various background and expertise independently selected "definite" or "possible" CMBs. Rating results were compared with respect to a specific consensus reference, on both lesion and subject type points of view.
IFM yielded increased sensitivity and decreased false positives rate (FPR) for CMBs identification compared to T2* magnitude and SWI-mIP images. Inter-rater variability was decreased with IFM when identifying subjects with numerous lesions, with only a limited increase in rating time. IFM thus appears as an interesting candidate to improve CMBs identification in clinical setting.
引言/目的：从T2梯度回波（GRE）幅度图像中对脑微出血（CMB）进行活体检测存在特异性低、评分者间再现性一般以及受采集参数敏感性影响而产生偏差等问题。已提出新方法来改进这种识别，但大多依赖于三维采集，在临床实践中并非总是可行。一种用于计算内部场图（IFM）的快速二维相位处理技术已被证明，基于二维多层采集，能够在常规临床环境中通过CMB的磁特征对其进行表征。然而，相对于更常见的图像，其在CMB识别方面的临床价值仍有待评估。为此，开展了系统实验，以比较训练有素的观察者对几种图像类型（T2幅度、磁敏感加权成像重建（SWI）以及基于相同T2加权采集构建的IFM）的评分。
材料/方法：从MEMENTO多中心队列中选取了15名参与者：6名有大量CMB（20±6个CMB）的受试者、5名有少量CMB（2±1个CMB）的受试者以及4名无CMB的受试者。在飞利浦和西门子3T系统上采集二维多层T2* GRE序列。经过预实验后，将T2*幅度、三层的磁敏感加权成像（SWI）最小强度投影（mIP）以及IFM用于评分实验。设计了一个图形用户界面（GUI），以便以随机顺序一致地显示图像。6名背景和专业知识各异的评分者独立选择“确定”或“可能”的CMB。从病变和受试者类型两个角度，将评分结果与特定的共识参考进行比较。
与T2*幅度和SWI - mIP图像相比，IFM在CMB识别中具有更高的灵敏度和更低的假阳性率（FPR）。在识别有大量病变的受试者时，使用IFM可降低评分者间的变异性，且评分时间仅略有增加。因此，IFM似乎是改善临床环境中CMB识别方面的一个有吸引力的候选方法。
