3 research outputs found
Muscle volume quantification: guiding transformers with anatomical priors
Muscle volume is a useful quantitative biomarker in sports, but also for the
follow-up of degenerative musculo-skelletal diseases. In addition to volume,
other shape biomarkers can be extracted by segmenting the muscles of interest
from medical images. Manual segmentation is still today the gold standard for
such measurements despite being very time-consuming. We propose a method for
automatic segmentation of 18 muscles of the lower limb on 3D Magnetic Resonance
Images to assist such morphometric analysis. By their nature, the tissue of
different muscles is undistinguishable when observed in MR Images. Thus, muscle
segmentation algorithms cannot rely on appearance but only on contour cues.
However, such contours are hard to detect and their thickness varies across
subjects. To cope with the above challenges, we propose a segmentation approach
based on a hybrid architecture, combining convolutional and visual transformer
blocks. We investigate for the first time the behaviour of such hybrid
architectures in the context of muscle segmentation for shape analysis.
Considering the consistent anatomical muscle configuration, we rely on
transformer blocks to capture the longrange relations between the muscles. To
further exploit the anatomical priors, a second contribution of this work
consists in adding a regularisation loss based on an adjacency matrix of
plausible muscle neighbourhoods estimated from the training data. Our
experimental results on a unique database of elite athletes show it is possible
to train complex hybrid models from a relatively small database of large
volumes, while the anatomical prior regularisation favours better predictions
Global sea-level budget 1993-present
Abstract. Global mean sea level is an integral of changes occurring in the climate system in response to unforced climate variability as well as natural and anthropogenic forcing factors. Its temporal evolution allows changes (e.g., acceleration) to be detected in one or more components. Study of the sea-level budget provides constraints on missing or poorly known contributions, such as the unsurveyed deep ocean or the still uncertain land water component. In the context of the World Climate Research Programme Grand Challenge entitled Regional Sea Level and Coastal Impacts, an international effort involving the sea-level community worldwide has been recently initiated with the objective of assessing the various datasets used to estimate components of the sea-level budget during the altimetry era (1993 to present). These datasets are based on the combination of a broad range of space-based and in situ observations, model estimates, and algorithms. Evaluating their quality, quantifying uncertainties and identifying sources of discrepancies between component estimates is extremely useful for various applications in climate research. This effort involves several tens of scientists from about 50 research teams/institutions worldwide (www.wcrp-climate.org/grand-challenges/gc-sea-level, last access: 22 August 2018). The results presented in this paper are a synthesis of the first assessment performed during 2017–2018. We present estimates of the altimetry-based global mean sea level (average rate of 3.1 ± 0.3 mm yr−1 and acceleration of 0.1 mm yr−2 over 1993–present), as well as of the different components of the sea-level budget (http://doi.org/10.17882/54854, last access: 22 August 2018). We further examine closure of the sea-level budget, comparing the observed global mean sea level with the sum of components. Ocean thermal expansion, glaciers, Greenland and Antarctica contribute 42 %, 21 %, 15 % and 8 % to the global mean sea level over the 1993–present period. We also study the sea-level budget over 2005–present, using GRACE-based ocean mass estimates instead of the sum of individual mass components. Our results demonstrate that the global mean sea level can be closed to within 0.3 mm yr−1 (1σ). Substantial uncertainty remains for the land water storage component, as shown when examining individual mass contributions to sea level.
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