RESUMEN
Objective.Automated biopsy needle segmentation in 3D ultrasound images can be used for biopsy navigation, but it is quite challenging due to the low ultrasound image resolution and interference similar to the needle appearance. For 3D medical image segmentation, such deep learning networks as convolutional neural network and transformer have been investigated. However, these segmentation methods require numerous labeled data for training, have difficulty in meeting the real-time segmentation requirement and involve high memory consumption.Approach.In this paper, we have proposed the temporal information-based semi-supervised training framework for fast and accurate needle segmentation. Firstly, a novel circle transformer module based on the static and dynamic features has been designed after the encoders for extracting and fusing the temporal information. Then, the consistency constraints of the outputs before and after combining temporal information are proposed to provide the semi-supervision for the unlabeled volume. Finally, the model is trained using the loss function which combines the cross-entropy and Dice similarity coefficient (DSC) based segmentation loss with mean square error based consistency loss. The trained model with the single ultrasound volume input is applied to realize the needle segmentation in ultrasound volume.Main results.Experimental results on three needle ultrasound datasets acquired during the beagle biopsy show that our approach is superior to the most competitive mainstream temporal segmentation model and semi-supervised method by providing higher DSC (77.1% versus 76.5%), smaller needle tip position (1.28 mm versus 1.87 mm) and length (1.78 mm versus 2.19 mm) errors on the kidney dataset as well as DSC (78.5% versus 76.9%), needle tip position (0.86 mm versus 1.12 mm) and length (1.01 mm versus 1.26 mm) errors on the prostate dataset.Significance.The proposed method can significantly enhance needle segmentation accuracy by training with sequential images at no additional cost. This enhancement may further improve the effectiveness of biopsy navigation systems.
Asunto(s)
Imagenología Tridimensional , Ultrasonografía , Imagenología Tridimensional/métodos , Agujas , Factores de Tiempo , Procesamiento de Imagen Asistido por Computador/métodos , Animales , Perros , Humanos , Aprendizaje Automático Supervisado , Biopsia con AgujaRESUMEN
Photosynthetic organisms have developed a set of mechanisms aimed at preventing photo-oxidative reactions in the photosynthetic apparatus (PSA) initiated by excessively absorbed light energy. Along with high irradiance, other stressors, e.g., chilling temperatures, can lead to the absorption of the excess of light energy and hence to photo-oxidative stress. Here, we studied induction of photoprotective mechanisms in response to chilling (0°C) at a low irradiance (50 µmol PAR photons m-2·s-1) in the cells of microalga Lobosphaera incisa IPPAS C-2047. After 4 days of incubation at a low temperature, L. incisa IPPAS C-2047 cells showed a notable decrease in the photochemical activity of photosystem II (PSII) and in the efficiency of photosynthetic electron transport, as well as a significant increase in the thermal dissipation of the absorbed light energy in the light-harvesting antenna. In contrast, most conventional markers of PSA acclimation to excess light energy [total chlorophyll and carotenoid content; violaxanthin cycle pigment content and de-epoxidation state; photosynthetic antenna, PSII, and photosystem I (PSI) ratio] remained virtually unchanged. The content of major unsaturated fatty acids also remained almost unaffected, except for arachidonic acid (increased by 40%) recently assumed to activate violaxanthin de-epoxidase by adjusting its lipid microenvironment. Significant changes (4-7-fold increase) were observed in the expression of the gene encoding protective protein LhcSR. Pre-conditioning at 5°C prior to the acclimation to 0°C augmented the PSA photochemical activity. Our data show that the mid-term (4-d) acclimation of L. incisa IPPAS C-2047 to a chilling temperature at a low irradiance triggers the PSA response resembling, in part, the response to high light but relying mostly on the LhcSR protein-dependent quenching of excitation in the photosynthetic antenna.