Although self-supervised learning methods based on masked image modeling have achieved some success in improving the performance of deep learning models, these methods have difficulty in ensuring that the masked region is the most appropriate for each image, resulting in segmentation networks that do not get the best weights in pre-training. Therefore, we propose a new adaptive-masking policy self-supervised learning method. Specifically, we model the process of masking images as a reinforcement learning problem and use the results of the reconstruction model as a feedback signal to guide the agent to learn the masking policy to select a more appropriate mask position and size for each image, helping the reconstruction network to learn more fine-grained image representation information and thus improve the downstream segmentation model performance. We conduct extensive experiments on two datasets, Cardiac and TCIA, and the results show that our approach outperforms current state-of-the-art self-supervised learning methods.

Pathological tremor is defined as a roughly sinusoidal movement and usually occurs in the upper limb impacting individuals activities of daily livings. Functional electrical stimulation (FES) is proposed as a potential alternative for cancelling the pathological tremor. However, the feasibility and accuracy of FES depends on the estimation of amplitude and frequency of tremor signals measured by sensors. In this study, a novel algorithm incorporating a sliding fast Fourier transform (SFFT), an interpolation procedure and a limitation module of frequency range is developed to estimate tremor frequency and separate the tremor components from raw data. Based on the artificial signals and the actual tremor signals, the performance of the proposed algorithm is evaluated. The experimental results indicate that the developed algorithm could quickly adapt to the unknown dominant frequency and extract the tremor components with high accuracy. Therefore, this method could be employed in the tremor suppression by FES without affecting the voluntary movement.