大象城南 (2022-03-14 11:32):
#paper doi:10.1186/s12938-020-00786-z 这篇文章主要介绍了被试间浅表层短联络纤维束自动聚类和标记算法。我们知道目前弥散加权磁共振成像是唯一能在活体状态下检测大脑白质纤维束走向的一种技术,以往的大部分脑白质纤维束追踪主要关注在深部走行的白质束,这些深层白质具有比较高的解剖一致性,被试间变异性较小,因此成熟的纤维束追踪算法和聚类算法可以很好地将深层白质分割成不同解剖位置的纤维束。基于深层白质的一些列研究(如脑发育,脑疾病异常的研究)均已经取得了很多突破和进展。然而浅表层纤维束由于其解剖结构比较复杂(大脑皮层有很多的沟回褶皱),且不同人大脑皮层形态差异性较大。因此常规的在深层白质追踪的算法直接套用在浅表层纤维束追踪往往是不合适的,且假阳性较高。本文基于匈牙利算法和Quick Bundle算法,对20个被试的dMRI进行浅表层纤维束追踪,并且建立了自动纤维聚类的方法,使得未来对浅表层白质纤维的挖掘提供了更精准的算法。他们的结果表明匈牙利算法虽然聚类后的质量较高,但是可重复性较差,而Quick Bundle算法具有较高的可重复性,能比较好地刻画群组之间的浅表层纤维束解剖特点。
Automatic group-wise whole-brain short association fiber bundle labeling based on clustering and cortical surface information
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Abstract:
BACKGROUND: Diffusion MRI is the preferred non-invasive in vivo modality for the study of brain white matter connections. Tractography datasets contain 3D streamlines that can be analyzed to study the main brain white matter tracts. Fiber clustering methods have been used to automatically group similar fibers into clusters. However, due to inter-subject variability and artifacts, the resulting clusters are difficult to process for finding common connections across subjects, specially for superficial white matter.METHODS: We present an automatic method for labeling of short association bundles on a group of subjects. The method is based on an intra-subject fiber clustering that generates compact fiber clusters. Posteriorly, the clusters are labeled based on the cortical connectivity of the fibers, taking as reference the Desikan-Killiany atlas, and named according to their relative position along one axis. Finally, two different strategies were applied and compared for the labeling of inter-subject bundles: a matching with the Hungarian algorithm, and a well-known fiber clustering algorithm, called QuickBundles.RESULTS: Individual labeling was executed over four subjects, with an execution time of 3.6 min. An inspection of individual labeling based on a distance measure showed good correspondence among the four tested subjects. Two inter-subject labeling were successfully implemented and applied to 20 subjects and compared using a set of distance thresholds, ranging from a conservative value of 10 mm to a moderate value of 21 mm. Hungarian algorithm led to a high correspondence, but low reproducibility for all the thresholds, with 96 s of execution time. QuickBundles led to better correspondence, reproducibility and short execution time of 9 s. Hence, the whole processing for the inter-subject labeling over 20 subjects takes 1.17 h.CONCLUSION: We implemented a method for the automatic labeling of short bundles in individuals, based on an intra-subject clustering and the connectivity of the clusters with the cortex. The labels provide useful information for the visualization and analysis of individual connections, which is very difficult without any additional information. Furthermore, we provide two fast inter-subject bundle labeling methods. The obtained clusters could be used for performing manual or automatic connectivity analysis in individuals or across subjects.
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