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融合常微分方程求解器的脑白质纤维高分辨深度重建方法研究

High-resolution deep reconstruction of white matter fibers via ODE-integrated modeling

  • 摘要: 扩散磁共振成像(diffusion magnetic resonance imaging,dMRI)是唯一能够无创、定量重建脑白质纤维走向的成像方法。基于纤维方向分布函数(fiber orientation distribution function,fODF)的纤维追踪可准确地表示多纤维走向分布,适用于脑组织内复杂纤维结构的重建。然而,fODF的拟合通常依赖于高角分辨率和多b值的dMRI数据,在一定程度上限制了其临床应用。深度学习由于其强大的非线性映射能力被用于直接从传统临床低b值、低角分辨率的dMRI信号重构高角分辨率fODF,但存在无法应对不同数据的输入以及缺少领域信息等问题。本研究通过融合深度学习网络和常微分方程(ordinary differential equation,ODE)求解器提出一种高分辨率重建模型(high resolution reconstruction model,HRRM)。该模型分为信号提取与高分辨率重构模块,信号方向特征提取模块采用3D卷积神经网络进行特征提取器;高分辨率重建模块则基于Adams-Bashforth-Moulton (ABM) ODE求解器建神经网络,实现从低角分辨率fODF球谐系数特征映射得到高角分辨率fODF球谐系数特征。HRRM模型可直接从传统临床dMRI数据生成高角分辨率fODF图像,不仅突破了低角分辨率临床数据的瓶颈,而且提高了脑白质纤维束分析的精度,为多种神经系统疾病的研究提供了可靠的技术支撑。

     

    Abstract: Diffusion magnetic resonance imaging (dMRI) is the only imaging method capable of noninvasively and quantitatively reconstructing the orientation of white matter fibers in the brain. Fiber tracking based on the fiber orientation distribution function (fODF) accurately represents the distribution of multiple fiber orientations, making it suitable for reconstructing complex fiber structures within brain tissue. However, fitting fODF typically relies on high-angular-resolution and multi-b-value dMRI data,which limits its clinical application to some extent. Deep learning, due to its powerful nonlinear mapping capabilities, has been employed to directly reconstruct high angular resolution fODF from conventional clinical low-b-value,low-angular-resolution dMRI signals. Yet,it faces challenges such as inability to handle diverse data inputs and a lack of domain-specific information. This study proposes a High Resolution Reconstruction Model (HRRM) by integrating deep learning networks with an Ordinary Differential Equation(ODE) solver. The model comprises two modules:1) a signal extraction module utilizing a 3D convolutional neural network to extract directional features; and 2) a high resolution reconstruction module that builds a neural network based on the Adams-Bashforth-Moulton (ABM) ODE solver to map low-angular-resolution fODF spherical harmonic coefficient features to their high-angular-resolution counterparts. The HRRM model directly generates high-angular-resolution fODF images from conventional clinical dMRI data, overcoming the limitations of low-resolution clinical data while enhancing the precision of white matter fiber tract analysis. This provides reliable technical support for research into various neurological disorders.

     

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