29 research outputs found
The Additional Symmetries for the BTL and CTL Hierarchies
The Toda lattice (TL) hierarchy was first introduced by K.Ueno and K.Takasaki
in \cite{uenotaksasai} to generalize the Toda lattice equations\cite{toda}.
Along the work of E. Date, M. Jimbo, M. Kashiwara and T. Miwa \cite{DJKM} on
the KP hierarchy, K.Ueno and K.Takasaki in \cite{uenotaksasai} develop the
theory for the TL hierarchy: its algebraic structure, the linearization, the
bilinear identity, function and so on. Also the analogues of the B and C
types for the TL hierarchy, i.e. the BTL and CTL hierarchies, are considered in
\cite{uenotaksasai}, which are corresponding to infinite dimensional Lie
algebras and respectively. In this
paper, we will focus on the study of the additional symmetries for the BTL and
CTL hierarchies.Comment: 13 page
Multi-scale Transformer Network with Edge-aware Pre-training for Cross-Modality MR Image Synthesis
Cross-modality magnetic resonance (MR) image synthesis can be used to
generate missing modalities from given ones. Existing (supervised learning)
methods often require a large number of paired multi-modal data to train an
effective synthesis model. However, it is often challenging to obtain
sufficient paired data for supervised training. In reality, we often have a
small number of paired data while a large number of unpaired data. To take
advantage of both paired and unpaired data, in this paper, we propose a
Multi-scale Transformer Network (MT-Net) with edge-aware pre-training for
cross-modality MR image synthesis. Specifically, an Edge-preserving Masked
AutoEncoder (Edge-MAE) is first pre-trained in a self-supervised manner to
simultaneously perform 1) image imputation for randomly masked patches in each
image and 2) whole edge map estimation, which effectively learns both
contextual and structural information. Besides, a novel patch-wise loss is
proposed to enhance the performance of Edge-MAE by treating different masked
patches differently according to the difficulties of their respective
imputations. Based on this proposed pre-training, in the subsequent fine-tuning
stage, a Dual-scale Selective Fusion (DSF) module is designed (in our MT-Net)
to synthesize missing-modality images by integrating multi-scale features
extracted from the encoder of the pre-trained Edge-MAE. Further, this
pre-trained encoder is also employed to extract high-level features from the
synthesized image and corresponding ground-truth image, which are required to
be similar (consistent) in the training. Experimental results show that our
MT-Net achieves comparable performance to the competing methods even using
of all available paired data. Our code will be publicly available at
https://github.com/lyhkevin/MT-Net.Comment: 13 pages, 15 figure
Automatic Data Augmentation via Deep Reinforcement Learning for Effective Kidney Tumor Segmentation
Conventional data augmentation realized by performing simple pre-processing
operations (\eg, rotation, crop, \etc) has been validated for its advantage in
enhancing the performance for medical image segmentation. However, the data
generated by these conventional augmentation methods are random and sometimes
harmful to the subsequent segmentation. In this paper, we developed a novel
automatic learning-based data augmentation method for medical image
segmentation which models the augmentation task as a trial-and-error procedure
using deep reinforcement learning (DRL). In our method, we innovatively combine
the data augmentation module and the subsequent segmentation module in an
end-to-end training manner with a consistent loss. Specifically, the best
sequential combination of different basic operations is automatically learned
by directly maximizing the performance improvement (\ie, Dice ratio) on the
available validation set. We extensively evaluated our method on CT kidney
tumor segmentation which validated the promising results of our method.Comment: 5 pages, 3 figure