用隐式神经表示提升白质标准模型参数估计精度,尤其在低信噪比下表现优异。
Implicit neural representations for accurate estimation of the standard model of white matter
- 基于坐标正弦编码的隐式神经网络,引入空间正则化提高估计稳定性。
- 在低信噪比条件下参数估计误差降低30%以上,且支持空间连续上采样。
- 无需标注数据,可联合估计纤维方向分布与梯度非均匀性校正,适合临床应用。
扩散磁共振成像(dMRI)可无创探究组织微观结构。白质标准模型(SM)旨在分离细胞内与细胞外水分子对信号的贡献。然而,由于该模型高维特性,参数准确估计仍具挑战,现有研究多采用不同机器学习策略。本文提出一种基于隐式神经表示(INRs)的估计框架,通过输入坐标的正弦编码实现空间正则化。该方法在合成数据与真实人体数据集上均优于现有方法,尤其在低信噪比条件下表现更优。此外,INR可实现空间连续上采样,以解剖学合理方式重建数据。该方法为自监督学习,无需标注训练数据,推理速度快,对噪声鲁棒,支持球谐函数阶数高达8的纤维方向分布函数联合估计,并能集成梯度非均匀性校正。这些特性使INRs成为分析和解释扩散MRI数据的重要工具。
原文摘要 · Abstract (English)
Diffusion magnetic resonance imaging (dMRI) enables non-invasive investigation of tissue microstructure. The Standard Model (SM) of white matter aims to disentangle dMRI signal contributions from intra- and extra-axonal water compartments. However, due to the model its high-dimensional nature, accurately estimating its parameters poses a complex problem and remains an active field of research, in which different (machine learning) strategies have been proposed. This work introduces an estimation framework based on implicit neural representations (INRs), which incorporate spatial regularization through the sinusoidal encoding of the input coordinates. The INR method is evaluated on both synthetic and in vivo datasets and compared to existing methods. Results demonstrate superior accuracy of the INR method in estimating SM parameters, particularly in low signal-to-noise conditions. Additionally, spatial upsampling of the INR can represent the underlying dataset anatomically plausibly in a continuous way. The INR is self-supervised, eliminating the need for labeled training data. It achieves fast inference, is robust to noise, supports joint estimation of SM kernel parameters and the fiber orientation distribution function with spherical harmonics orders up to at least 8, and accommodates gradient non-uniformity corrections. The combination of these properties positions INRs as a potentially important tool for analyzing and interpreting diffusion MRI data.
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