Ricardo (2022-01-22 17:06):
#paper doi:10.1109/TMI.2021.3137280 Recurrent Tissue-Aware Network for Deformable Registration of Infant Brain MR Images. 介绍一篇21年末发表在TMI上的文章。众所周知,非线性配准技术是一种用于纵向发育分析和群体分析的基础技术。然而由于出生后的两年时间里,婴幼儿大脑处于快速发育过程中,对同一个被试的不同发育时间点的婴儿脑图像或者对不同被试的婴幼儿脑图像进行精细的配准是一件非常困难的事。主要有几点原因:1.婴幼儿大脑处于持续的髓鞘化进程,脑图像体素强度呈现出区域间的不一致性;2.0~2岁这个阶段婴幼儿大脑图像的信号强度会出现反转的变化,这使得纵向图像的配准变得更加困难;3.婴幼儿大脑非常小,而大脑组织结构又相对比较复杂,并且还存在许多图像噪声及伪影。所以这篇文章干脆不对MRI强度信号图像进行配准,而是使用基于T1/T2图像的脑组织分割图进行配准,这样就规避了出生后的头两年大脑组织信号强度的快速变化的问题。这篇文章主要有两个创新点:1.只对模型做一次训练,但是在测试阶段进行多次配准,一步步对脑图像的形变场进行finetune;2.作者将速度场建模成一个多元高斯场,每个体素都服从高斯分布。并给予速度场的方差建模形变场的不确定度(uncertainty),并基于这样的uncertainty对形变场进行动态平滑(adaptive smoothing),而非以往的全局平滑。具体结果当然要比其他方法更好啦,这个没啥说的。不过这个方法的局限在于需要精细分割后的脑组织图像,而对婴幼儿的脑图像进行组织分割又是一个非常困难的事啊(就是又缺数据又难打label)。
Recurrent Tissue-Aware Network for Deformable Registration of Infant Brain MR Images
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Abstract:
Deformable registration is fundamental to longitudinal and population-based image analyses. However, it is challenging to precisely align longitudinal infant brain MR images of the same subject, as well as cross-sectional infant brain MR images of different subjects, due to fast brain development during infancy. In this paper, we propose a recurrently usable deep neural network for the registration of infant brain MR images. There are three main highlights of our proposed method. (i) We use brain tissue segmentation maps for registration, instead of intensity images, to tackle the issue of rapid contrast changes of brain tissues during the first year of life. (ii) A single registration network is trained in a one-shot manner, and then recurrently applied in inference for multiple times, such that the complex deformation field can be recovered incrementally. (iii) We also propose both the adaptive smoothing layer and the tissue-aware anti-folding constraint into the registration network to ensure the physiological plausibility of estimated deformations without degrading the registration accuracy. Experimental results, in comparison to the state-of-the-art registration methods, indicate that our proposed method achieves the highest registration accuracy while still preserving the smoothness of the deformation field. The implementation of our proposed registration network is available online https://github.com/Barnonewdm/ACTA-Reg-Net.
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