112 research outputs found
Self-training with dual uncertainty for semi-supervised medical image segmentation
In the field of semi-supervised medical image segmentation, the shortage of
labeled data is the fundamental problem. How to effectively learn image
features from unlabeled images to improve segmentation accuracy is the main
research direction in this field. Traditional self-training methods can
partially solve the problem of insufficient labeled data by generating pseudo
labels for iterative training. However, noise generated due to the model's
uncertainty during training directly affects the segmentation results.
Therefore, we added sample-level and pixel-level uncertainty to stabilize the
training process based on the self-training framework. Specifically, we saved
several moments of the model during pre-training, and used the difference
between their predictions on unlabeled samples as the sample-level uncertainty
estimate for that sample. Then, we gradually add unlabeled samples from easy to
hard during training. At the same time, we added a decoder with different
upsampling methods to the segmentation network and used the difference between
the outputs of the two decoders as pixel-level uncertainty. In short, we
selectively retrained unlabeled samples and assigned pixel-level uncertainty to
pseudo labels to optimize the self-training process. We compared the
segmentation results of our model with five semi-supervised approaches on the
public 2017 ACDC dataset and 2018 Prostate dataset. Our proposed method
achieves better segmentation performance on both datasets under the same
settings, demonstrating its effectiveness, robustness, and potential
transferability to other medical image segmentation tasks. Keywords: Medical
image segmentation, semi-supervised learning, self-training, uncertainty
estimatio
A region and category confidence-based multi-task network for carotid ultrasound image segmentation and classification
The segmentation and classification of carotid plaques in ultrasound images
play important roles in the treatment of atherosclerosis and assessment for the
risk of stroke. Although deep learning methods have been used for carotid
plaque segmentation and classification, two-stage methods will increase the
complexity of the overall analysis and the existing multi-task methods ignored
the relationship between the segmentation and classification. These will lead
to suboptimal performance as valuable information might not be fully leveraged
across all tasks. Therefore, we propose a multi-task learning framework
(RCCM-Net) for ultrasound carotid plaque segmentation and classification, which
utilizes a region confidence module (RCM) and a sample category confidence
module (CCM) to exploit the correlation between these two tasks. The RCM
provides knowledge from the probability of plaque regions to the classification
task, while the CCM is designed to learn the categorical sample weight for the
segmentation task. A total of 1270 2D ultrasound images of carotid plaques were
collected from Zhongnan Hospital (Wuhan, China) for our experiments. The
results showed that the proposed method can improve both segmentation and
classification performance compared to existing single-task networks (i.e.,
SegNet, Deeplabv3+, UNet++, EfficientNet, Res2Net, RepVGG, DPN) and multi-task
algorithms (i.e., HRNet, MTANet), with an accuracy of 85.82% for classification
and a Dice-similarity-coefficient of 84.92% for segmentation. In the ablation
study, the results demonstrated that both the designed RCM and CCM were
beneficial in improving the network's performance. Therefore, we believe that
the proposed method could be useful for carotid plaque analysis in clinical
trials and practice
Dual uncertainty-guided multi-model pseudo-label learning for semi-supervised medical image segmentation
Semi-supervised medical image segmentation is currently a highly researched area. Pseudo-label learning is a traditional semi-supervised learning method aimed at acquiring additional knowledge by generating pseudo-labels for unlabeled data. However, this method relies on the quality of pseudo-labels and can lead to an unstable training process due to differences between samples. Additionally, directly generating pseudo-labels from the model itself accelerates noise accumulation, resulting in low-confidence pseudo-labels. To address these issues, we proposed a dual uncertainty-guided multi-model pseudo-label learning framework (DUMM) for semi-supervised medical image segmentation. The framework consisted of two main parts: The first part is a sample selection module based on sample-level uncertainty (SUS), intended to achieve a more stable and smooth training process. The second part is a multi-model pseudo-label generation module based on pixel-level uncertainty (PUM), intended to obtain high-quality pseudo-labels. We conducted a series of experiments on two public medical datasets, ACDC2017 and ISIC2018. Compared to the baseline, we improved the Dice scores by 6.5% and 4.0% over the two datasets, respectively. Furthermore, our results showed a clear advantage over the comparative methods. This validates the feasibility and applicability of our approach
A dual de-icing system for wind turbine blades combining high-power ultrasonic guided waves and low-frequency forced vibrations
Developing a Novel Ice Protection System for Wind Turbine Blades Using Vibrations of Both Short and Long Wavelengths
Äimbenik prirodne obnove vrste Platycladus orientalis (L.) Franco u Guilinu, Kina
Cypress (Platycladus orientalis (L.) Franco) is one of the important evergreen trees for afforestation in barren mountains, soil consolidation, and water conservation, but natural regeneration of cypress is complex and slow. An understanding of the influence mechanism of the natural regeneration of cypresses is essential for elevating survival and regeneration. This study aimed to clarify the relationship between stand factors, environmental factors, and regeneration of cypress plantations. A total of 42 cypress sample plots in Guilin, China, were selected to evaluate the impact of various stand factors and environmental factors on the regeneration of cypresses using survey statistics and Pearson and Spearmanrank correlation analysis. In this study, cypress has the highest frequency and density of regeneration among all the seedlings in the 18 surveyed forests, but the height structure of cypress seedlings distributes in uneven mode and mainly Grade I (height < 30 cm) seedlings. Low-density herbs and high-density moss mulching had a directly positive effect on the number of cypress regeneration seedlings. Larger soil stone content and gap area can promote cypress regeneration, which is appropriate for cypresses in the seedling stage. In conclusion, timely weeding, proper soil loosening, and improving light transmittance contribute to promoting the regeneration of cypresses.ObiÄna azijska tuja (Platycladus orientalis (L.) Franco) je jedno od važnih zimzelenih stabala za poÅ”umljavanje u neplodnim planinama, za konsolidaciju tla i oÄuvanje vode, ali prirodna regeneracija obiÄne azijske tuje je složena i spora. Razumijevanje mehanizma utjecaja na prirodnu regeneraciju obiÄne azijske tuje bitno je za poticanje preživljavanja i regeneraciju. Cilj ovog istraživanja je objasniti odnos izmeÄu Å”umskih sastojina, okoliÅ”nih Äimbenika i regeneracije nasada obiÄne azijske tuje. Ukupno 42 uzorka Äempresa u Guilinu, Kina, odabrane su za procjenu utjecaja razliÄitih Äimbenika sastojine i okoliÅ”nih Äimbenika na regeneraciju Äempresa koriÅ”tenjem statistike ankete i korelacijske analize Pearson i Spearmanrank. U ovoj studiji, obiÄna azijska tuja ima najveÄu uÄestalost i gustoÄu regeneracije meÄu svim sadnicama ( 18 ) u istraživanoj Å”umi, ali je visinska struktura sadnica obiÄne azijske tuje rasporeÄena neravnomjerno, a radi se uglavnom o sadnicama I klase (visina < 30 cm). Bilje niske gustoÄe i malÄiranje mahovine velike gustoÄe, imali su izravan pozitivan uÄinak na broj sadnica za regeneraciju obiÄne azijske tuje. VeÄi sadržaj kamena u tlu i opustoÅ”enih povrÅ”ina mogu potaknuti regeneraciju obiÄne azijske tuje, ali je to prikladnije za obiÄne azijske tuje u fazi sadnice. ZakljuÄno, pravodobno plijevljenje korova, pravilno rahljenje tla i poboljÅ”anje propusnosti svjetla mogli bi potaknuti regeneraciju obiÄne azijske tuje
Performance analysis of RIS-assisted cell-free massive MIMO systems with transceiver hardware impairments
Integrating reconfigurable intelligent surface (RIS) into cell-free massive multiple-input multiple-output (MIMO) is a promising approach to enhance the coverage quality, spectral efficiency (SE), and energy efficiency. In this paper, an RIS-assisted cell-free massive MIMO downlink system suffering from the transceiver hardware impairments (T-HWIs) is investigated. To improve the accuracy of the direct estimation (DE) scheme, a modified ON/OFF estimation (MOE) with moderate pilot overhead is proposed. Relying on the knowledge of imperfect channel state information, we derive closed-form expressions of the lower-bound achievable SE with T-HWIs under both DE and MOE schemes. The closed-form results facilitate the investigation of how RIS improves the downlink SE under various system settings and allow us to explore the trade-off strategies between using more hardware-impaired APs and low-cost RISs in terms of the downlink SE and power consumption. Numerical results validate the theoretical analysis and show that the proposed MOE scheme outperforms the DE scheme in terms of the downlink SE. Moreover, the benefits of introducing RIS into hardware-impaired cell-free massive MIMO systems are also illustrated
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