Re: Auto Uh Tibia 7.6 Download
Joao Charlesbois
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The ability to efficiently and reproducibly generate subject-specific 3D models of bone and soft tissue is important to many areas of musculoskeletal research. However, methodologies requiring such models have largely been limited by lengthy manual segmentation times. Recently, machine learning, and more specifically, convolutional neural networks, have shown potential to alleviate this bottleneck in research throughput. Thus, the purpose of this work was to develop a modified version of the convolutional neural network architecture U-Net to automate segmentation of the tibia and femur from double echo steady state knee magnetic resonance (MR) images. Our model was trained on a dataset of over 4,000 MR images from 34 subjects, segmented by three experienced researchers, and reviewed by a musculoskeletal radiologist. For our validation and testing sets, we achieved dice coefficients of 0.985 and 0.984, respectively. As further testing, we applied our trained model to a prior study of tibial cartilage strain and recovery. In this analysis, across all subjects, there were no statistically significant differences in cartilage strain between the machine learning and ground truth bone models, with a mean difference of 0.2 0.7 % (mean 95 % confidence interval). This difference is within the measurement resolution of previous cartilage strain studies from our lab using manual segmentation. In summary, we successfully trained, validated, and tested a machine learning model capable of segmenting MR images of the knee, achieving results that are comparable to trained human segmenters.
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The auto-cleaning system in digging forelegs of the Congo rose chafer Pachnoda marginata femoro-tibial joint is described. The cleaning system consists of four subsystems: three external ones represented by microsetal pad, hairy brush and scraper and one internal one. They work proactively not only removing contaminants, but also preventing them from entering the joint. The principle of functioning of the cleaning system is based on the sliding of the contacting surfaces of the joint, equipped with hairs, bristles and scrapers. The mutual movement of such surfaces leads to the shift of contaminating particles and, ultimately, to their removal from surfaces of the joint. The key feature of the joint cleaning system is its complete autonomy, in which cleaning is performed constantly with each movement of the femoro-tibial joint without special actions required from the insect. The difference between the auto-cleaning system and self-cleaning and active grooming is also discussed.
For the majority of organisms, staying clean is perhaps just as important as staying healthy. The environment continuously supplies a wide variety of organic and inorganic pollutants in all three phases: gaseous, liquid, and solid. Living organisms have evolved many mechanisms to stay clean and minimize the effects of contamination1. Small-sized animals, such as insects, are particularly sensitive to the external contamination, because their exoskeleton provides various functional roles, such as mechanical support, excretion, protection, feeding, sensing, and acting as a barrier against desiccation2,3.
Active cleaning by grooming in insect involves the mechanical removal of contaminants and is performed with a variety of behaviorally determined movements that can be accompanied by the various specialized morphological structures11. As a multipurpose behavior, grooming is also executed to spread the gland secretions over the body, removing ectoparasites, to prevent bacterial and fungal fouling and to enhance olfactory acuity12,13. Insects are able to groom various parts of their body: antennae, head, legs, thorax, wings, and abdomen14,15,16,17. However, not all body parts are equally available for grooming that can be constrained, e.g., by the body shape and motility of limbs and other body joints11.
In this paper, an automatically working cleaning system has been revealed in the femoro-tibial joint of digging legs of the beetle Pachnoda marginata (Coleoptera: Scarabaeidae) (Fig. 1a), establishing a new type of anti-contamination mechanism in insects. Using the originally developed experimental method based on the CT technique and scanning electron microscopy, we for the first time demonstrated biomechanical principle behind such an auto-cleaning mechanism in the leg joints of beetles.
Penetration of the contaminating particles can generally happen through the gaps between the tibial and femoral counterparts of the joint. There are two major gap areas in the joint: dorsal gap and ventral gap (Fig. 1b, e).
The digging legs of Pachnoda marginata, as follows from the experimental data, are able to some extent to resist external contamination by particles (e.g., soil) with the help of specialized structures organized into a joint cleaning system (Figs. 5 and 6). The functioning of each of these structures acting in concert is discussed in more detail below.
Experimental results indicate that the penetration of contaminants through the dorsal gap is hampered by the presence of the microsetal pad and the membraneous plate (Fig. 5a). The mechanism of functioning of this cleaning system is supposed as follows (Fig. 6a). The particles of the substrate are in contact with the microsetal pad, being located, depending on the size, both among the setae and on the surface of the pad. When extending the tibia, the microsetal pad moves directly under the membraneous plate, while the distance between the tibia and femur in this region is minimal. As a result of the translational movement, the membraneous plate displaces (scrapes) particles from the surface of the pad, the size of which exceeds the size of the gap between the membraneous plate and microsetal pad. Since the orientation of the bristles is co-directed with the movement of tibia during its extension, the setae of the microsetal pad do not impede the movement of the membraneous plate over its surface. In addition, the bristles may reduce the contact area of the particles with the underlying cuticle surface, i.e., they minimize the possibility of stiction by adhesion. It can be assumed that as a result of this, the particles that are on the bristles and are stuck among the setae are unstable and can be easily displaced by the membraneous plate.
The hairy brush appears to be a barrier against penetration of particles through the ventral gap. As follows from our observations, the hairs fill the space between the femur and tibia as fully as possible at an angle of no more than 90 (Fig. 5d). As shown in our experiments, flexion of the tibia to the femur results in the particle displacement (pushing out) and cleaning of the femoral surface. This is achieved due to several features. (1) The setae are curved and their curvature corresponds to the curvature of the femoral surface. (2) The length of the setae gradually decreases in the distal direction of the tibia. (3) The angle of inclination of the setae changes from approximately straight for the longer setae on the tibial base to the sharp one for the shorter setae situated more distally. Thus, the cleaning mechanism by means of the hairy brush can be described as follows (Fig. 6d). When the tibia starts moving, the longer setae situated closer to the base lie down on the femoral surface and begin to move along it. As the tibia approaches the femur, more and more setae come into contact with the femur surface. In this case, due to the corresponding angle of inclination of the setae, the latter orient parallel to the femur surface. At the same time, the density of the setae increases, and the distance between them decreases. The movement of setae along the surface of the femur leads to the displacement of particles proximally relative to the femur, that is, further from the ventral gap. This is also facilitated by the presence of notches on the surface of setae, whose sharp tips are directed from the base to the apex (Supplementary Fig. S1n). Obviously, the role of the notches is to prevent the movement of particles between the setae. This arrangement of notches on one setal side increases and prevents the movement of particles between the setae. Also, the arrangement of notches promotes pushing the particles out, when the setae move relatively to each other. Some notches trap the particles, whereas the others (from adjacent hairs) scrape them towards the tips of the setae.
Thus, the auto-cleaning system of Pachnoda marginata leg joint is represented by the structural and functional complex of structures, which can be subdivided into four subsystems: (1) microsetal pad/membraneous plate, (2) internal cleaning subsystem, (3) hairy brush, and (4) scraper (Figs. 5 and 6). Two of these subsystems, namely the first and the third ones, not only clean the outer parts of the joint, but also prevent the penetration of particles into the joint cavity, performing a barrier function. The mutual arrangement of surfaces, the structure and orientation of their structural surface elements result in their interaction at every movement of the joint, i.e., flexion-extension of a tibia, which in turn leads to the removal of contaminant particles to the outside of the joint. This cleaning mechanism working exclusively due to the structural and functional organization of the joint and not requiring any special actions is considered here as automatic cleaning system.
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