Developmental Neurosciences Research and Teaching Department, UCL Great Ormond Street Institute of Child Health, University College London, London, UK.
Department of Medical Physics and Biomedical Engineering, University College London, London, UK.
Hum Brain Mapp. 2024 Feb 1;45(2):e26578. doi: 10.1002/hbm.26578.
Fibre tract delineation from diffusion magnetic resonance imaging (MRI) is a valuable clinical tool for neurosurgical planning and navigation, as well as in research neuroimaging pipelines. Several popular methods are used for this task, each with different strengths and weaknesses making them more or less suited to different contexts. For neurosurgical imaging, priorities include ease of use, computational efficiency, robustness to pathology and ability to generalise to new tracts of interest. Many existing methods use streamline tractography, which may require expert neuroimaging operators for setting parameters and delineating anatomical regions of interest, or suffer from as a lack of generalisability to clinical scans involving deforming tumours and other pathologies. More recently, data-driven approaches including deep-learning segmentation models and streamline clustering methods have improved reproducibility and automation, although they can require large amounts of training data and/or computationally intensive image processing at the point of application. We describe an atlas-based direct tract mapping technique called 'tractfinder', utilising tract-specific location and orientation priors. Our aim was to develop a clinically practical method avoiding streamline tractography at the point of application while utilising prior anatomical knowledge derived from only 10-20 training samples. Requiring few training samples allows emphasis to be placed on producing high quality, neuro-anatomically accurate training data, and enables rapid adaptation to new tracts of interest. Avoiding streamline tractography at the point of application reduces computational time, false positives and vulnerabilities to pathology such as tumour deformations or oedema. Carefully filtered training streamlines and track orientation distribution mapping are used to construct tract specific orientation and spatial probability atlases in standard space. Atlases are then transformed to target subject space using affine registration and compared with the subject's voxel-wise fibre orientation distribution data using a mathematical measure of distribution overlap, resulting in a map of the tract's likely spatial distribution. This work includes extensive performance evaluation and comparison with benchmark techniques, including streamline tractography and the deep-learning method TractSeg, in two publicly available healthy diffusion MRI datasets (from TractoInferno and the Human Connectome Project) in addition to a clinical dataset comprising paediatric and adult brain tumour scans. Tract segmentation results display high agreement with established techniques while requiring less than 3 min on average when applied to a new subject. Results also display higher robustness than compared methods when faced with clinical scans featuring brain tumours and resections. As well as describing and evaluating a novel proposed tract delineation technique, this work continues the discussion on the challenges surrounding the white matter segmentation task, including issues of anatomical definitions and the use of quantitative segmentation comparison metrics.
从弥散磁共振成像(MRI)中描绘纤维束是神经外科规划和导航以及神经影像学研究管道的有价值的临床工具。有几种流行的方法可用于此任务,每种方法都有不同的优缺点,使其或多或少适用于不同的情况。对于神经外科成像,优先考虑的是易用性、计算效率、对病理学的鲁棒性以及将其推广到新的感兴趣的束的能力。许多现有的方法都使用流线追踪技术,这可能需要神经影像学专家来设置参数并描绘感兴趣的解剖区域,或者由于缺乏对涉及变形肿瘤和其他病理学的临床扫描的可推广性而受到影响。最近,基于数据的方法,包括深度学习分割模型和流线聚类方法,提高了可重复性和自动化程度,尽管它们可能需要大量的训练数据和/或在应用时需要计算密集型图像处理。我们描述了一种基于图谱的直接束映射技术,称为“束发现者”,该技术利用束特定的位置和方向先验。我们的目标是开发一种临床实用的方法,避免在应用时使用流线追踪,同时利用仅从 10-20 个训练样本中得出的解剖学先验知识。需要少量的训练样本可以强调产生高质量、神经解剖准确的训练数据,并能够快速适应新的感兴趣的束。避免在应用时使用流线追踪可以减少计算时间、假阳性和对病理学的脆弱性,例如肿瘤变形或水肿。仔细过滤的训练流线和轨迹方向分布映射用于在标准空间中构建束特定的方向和空间概率图谱。然后使用仿射配准将图谱转换到目标主体空间,并使用分布重叠的数学度量与主体的体素纤维方向分布数据进行比较,从而得到束的可能空间分布的映射。这项工作包括广泛的性能评估,并与基准技术(包括流线追踪和深度学习方法 TractSeg)进行比较,除了包括儿科和成人脑肿瘤扫描的临床数据集外,还在两个公开的健康弥散 MRI 数据集(来自 TractoInferno 和人类连接组计划)中进行了比较。束分割结果与已建立的技术具有高度一致性,而对新主体的平均应用时间不到 3 分钟。与面对具有肿瘤和切除术的临床扫描的比较方法相比,结果还显示出更高的鲁棒性。除了描述和评估一种新提出的束描绘技术外,这项工作还继续讨论了与白质分割任务相关的挑战,包括解剖定义问题和使用定量分割比较指标的问题。
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