arXiv:2511.03893eess.IV2025-11中稿 · SPIE Medical Imagi…

用神经网络加速脑白质纤维分离,精度高且速度快。

DeepFixel: Crossing white matter fiber identification through spherical convolutional neural networks

  • 用球面卷积网络替代传统非凸优化,实现高效纤维方向估计。
  • 在0.32毫秒/体素下完成计算,精度接近最优方法。
  • 能分辨更小角度和更小体积分数的交叉纤维,适合高精度脑连接研究。

弥散加权磁共振成像可重建大脑结构连接模型,如描述体素内白质纤维束分布、方向与体积的纤维取向分布函数(ODFs)。体素内交叉纤维增加分析复杂性,可能导致轨迹追踪等下游任务出错。本文提出DeepFixel,一种基于球面卷积神经网络的非凸优化近似方法,通过拟合数据并惩罚非轴对称项来分离纤维ODFs。模型采用比截断球谐表示更高角分辨率的球面网格表示纤维概率分布。在双纤维和三纤维ODFs上验证,与非凸优化(中位角相关系数1,四分位距0.00)、固定束元素(fixel)算法(0.988,0.317)相比,DeepFixel达到0.973(0.004)的中位角相关系数,计算效率显著提升至0.32毫秒/体素。其球面网格表示在更小角度间隔和更低体积分数下仍能有效解缠纤维,优于传统fixel方法。

原文摘要 · Abstract (English)

Diffusion-weighted magnetic resonance imaging allows for reconstruction of models for structural connectivity in the brain, such as fiber orientation distribution functions (ODFs) that describe the distribution, direction, and volume of white matter fiber bundles in a voxel. Crossing white matter fibers in voxels complicate analysis and can lead to errors in downstream tasks like tractography. We introduce one option for separating fiber ODFs by performing a nonlinear optimization to fit ODFs to the given data and penalizing terms that are not symmetric about the axis of the fiber. However, this optimization is non-convex and computationally infeasible across an entire image (approximately 1.01 x 106 ms per voxel). We introduce DeepFixel, a spherical convolutional neural network approximation for this nonlinear optimization. We model the probability distribution of fibers as a spherical mesh with higher angular resolution than a truncated spherical harmonic representation. To validate DeepFixel, we compare to the nonlinear optimization and a fixel-based separation algorithm of two-fiber and three-fiber ODFs. The median angular correlation coefficient is 1 (interquartile range of 0.00) using the nonlinear optimization algorithm, 0.988 (0.317) using a fiber bundle elements or "fixel"-based separation algorithm, and 0.973 (0.004) using DeepFixel. DeepFixel is more computationally efficient than the non-convex optimization (0.32 ms per voxel). DeepFixel's spherical mesh representation is successful at disentangling at smaller angular separations and smaller volume fractions than the fixel-based separation algorithm.

脑连接纤维分离球面网络神经影像

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