深度学习建模曲线形状,支持多模态高维数据,用于医学影像分析。
Deep Shape Regression for Planar Curves with Multimodal Covariates
- 用复数函数表示曲线,结合模态特异性编码器建模条件协方差。
- 可处理稀疏不规则采样曲线,准确估计弹性均值与协变效应。
- 适用于神经影像等医疗场景,如阿尔茨海默病患者海马体轮廓分析。
平面曲线的形状是去除平移、旋转、缩放和重参数化后保留的几何信息,在神经影像等健康应用中具有重要意义。本文提出一种针对开放平面曲线的深度形状回归模型,可处理多模态和高维协变量。将曲线表示为复值函数,证明条件全普鲁克斯特均值是条件协方差的主特征函数。为估计该协方差表面,提出一种新型深度条件协方差平滑器,采用模态特异性编码器(如标量协变量用样条,图像协变量用卷积网络),传统样条平滑器无法实现此功能。模型在构造上对输入曲线的平移、旋转和缩放保持不变性,并能处理稀疏不规则采样曲线。进一步提供一种弹性均值估计算法,通过迭代协方差平滑、旋转对齐和参数化对齐来消除参数化影响。在具有已知条件均值和多模态协变量的模拟轮廓上验证方法,首次应用于ADNI队列中的海马体轮廓,恢复的协变效应与文献一致。代码见https://github.com/mpff/dnn-shapes。
原文摘要 · Abstract (English)
The shape of a planar curve is the geometric information that remains once translation, rotation, scale and reparametrisation are removed and is of interest in many health applications, e.g. in neuroimaging. We propose a deep shape regression model for open planar curves that admits multimodal and high-dimensional covariates. Representing curves as complex-valued functions, we show that the conditional full Procrustes mean is the leading eigenfunction of the conditional covariance. To estimate this covariance surface, we propose a novel deep conditional covariance smoother with modality-specific encoders - e.g. splines for scalar covariates and convolutional networks for images, which classical spline smoothers cannot accommodate. Our model is by construction invariant to the translation, rotation and scaling of the input curves and handles sparsely and irregularly sampled curves. We further provide an algorithm for elastic mean estimation that also removes parametrisation by iterating covariance smoothing, rotational alignment and parametrisation alignment. We illustrate the method on simulated outlines with known conditional mean and multimodal covariates, and give a first application to hippocampal outlines from the ADNI cohort, recovering covariate effects consistent with the literature. Code is available at https://github.com/mpff/dnn-shapes.
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