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2-D kinematics of the shank and foot complex during stance using markerless segmentation and body-segment anatomical axes identification
No full textIn this work, a markerless motion capture method is proposed for the 2-D description of the movement of the shank and foot complex. The video sequences of subjects walking wearing socks or barefoot, were segmented isolating the moving regions from the background. Anatomical axes of a three-segment model of the shank and foot complex were identified using two different methods applied to the segmented images: 1) skeletonization and line detection and 2) cross-correlation of selected image regions. The axes identified were used to determine the kinematics on the sagittal plane of the two joints included in the model. Results from the segmentation of the images are independent from the presence of the socks, allowing the definition of more flexible acquisition protocols. Joint kinematics estimation with both methods appeared to be comparable to that obtained with more traditional marker-based methods. The cross-correlation method, which includes the calibration of the anatomy of the body-segments, may provide more robust solutions for the extension to a 3-D analysis of the shank and foot complex kinematics compared to the other proposed method
Assessment of lower limb joint kinematics using a 2-D hybrid markerless approach applied to a video camcorder acquisition
No full textIn this study, a 2-D hybrid markerless technique is proposed to estimate the lower limb joint kinematics
from data recorded using a video camcorder. The presented markerless methodology is defined as
hybrid because garments like high-cut underwear and ankle socks were used as “segmental markers”.
High-cut underwear contributed in defining the pelvis segment and ankle socks are used for the
definition of the foot segment. The method was applied to a video sequence acquired with a video
camcorder. The method was validated by using a stereophotogrammetric marker-based system.
Correlation and Root Mean Square Deviation (RMSD) of the joint kinematics estimates obtained with
the two techniques were found to be similar. The proposed hybrid technique can be considered as an
easy-to-configure and affordable alternative to marker-based photogrammetric systems for the
estimation of the lower limb joint kinematics
Shank-foot complex 2-D kinematics during stance using markerless segmentation and body-segment anatomical axes identification
No full textShank and foot complex is considered to be a fundamental mechanism of the lower limb in locomotion.
Typically marker based techniques are used to analyze the shank and foot kinematics. Three markers per segment are mounted. The disadvantages of this technique are the complexity stemming from the number of markers per segment and the interference of markers with the subject and the subject’s movement.
In this work, a markerless approach, which uses the 2-D images acquired by a digital camera, is proposed. The shank-foot complex is defined as a three-segment model by applying image processing techniques to the images of a subject walking in both barefoot and socked conditions. The aims of the current technique can be summarized as: (1) to ease the process of data acquisition by eliminating the markers and including the possibility of wearing socks; (2) to track the shank–foot complex kinematics with a three-segmented model
Markerless shank and foot segmentation and skeletonization for lower limb 2-D movement analysis during the stance phase in gait
No full textA method for analyzing the 2-D movement of the shank and foot complex during stance is
presented. A single camera acquiring at 50 frames per second was positioned laterally to the
subject in order to obtain an approximate sagittal view of the shank and foot during the stance
phase. Experiments were performed in two conditions: with the subject barefoot and wearing
socks. Shank and foot were first separated from the background and then shank, rear-foot and
fore-foot were identified. The background/foreground separation (segmentation) was
achieved by using Mixture of Gaussians (MoG) method while the lower limb segment
definition (skeletonization) was done by using Medial Axis Transform (MAT). The results of
the segmentation showed that the presence of socks did not affect the performance of the
segmentation algorithm. The skeletonization showed that a three-segmented model could
successfully be fit to the portion of the lower limb under analysis. For each frame of the
stance phase, three lines representing the three segments could be fit to the skeletonized
images and therefore a full 2-D movement analysis could be obtained. The proposed method
not only represents a good alternative to marker-based methods but also offers at least two
potential advantages: the option of wearing socks during the trials and the possibility of
describing the relative movement between fore-foot and rear-foot
2-D Lower limb joint kinematics using a hybrid markerless approach applied to video camcorder acquisitions
No full textA hybrid markerless technique is presented
and applied to estimate the 2-D lower limb joint
kinematics from acquisitions recorded using a video
camcorder. The proposed methodology is defined as
hybrid since it uses garments as “segmental markers”,
specifically high-cut underwear which contributes in
defining the pelvis segment and ankle socks for the
definition of the foot segment. The method was applied to
video sequences acquired with a video camcorder and was
validated by using a stereophotogrammetric markerbased
system. Results show that the proposed technique
can be considered as an easy-to-configure and affordable
alternative to marker-based photogrammetric systems
Measurement of knee flexion/extension using a 2-D markerless technique
No full textSeveral measurement tools are typically used in assessing knee flexion/extension: electro-goniometers,
inertial sensors, 2-D and 3-D marker based motion analysis systems [1]. Most of the traditional
clinical analysis methods require applying sensors to the patients, which may cause discomfort and
hinder the natural movement. To overcome the aforementioned limitations, in this study, we propose a
2-D markerless technique to measure knee flexion/extension. This study is an enhancement of our
previous markerless technique [2]. The focus of the first study was the analysis of the 2-D kinematics
of the shank and foot complex using a single lateral view by defining a three-segment model and
tracking its movement using selected patches rigid to the segment. To simplify the problem, a black
background was used and the subjects wore long black socks to cover the contra-lateral leg. In this
study, we developed a markerless technique, which does require neither a black background nor a
black long sock on the contra-lateral leg. The presence of a more complex background was dealt with
by using an adaptive statistical background subtraction model, while the removal of the long black
sock on the contra-lateral leg resulted in occlusions that are dealt with by defining an additional patch
per segment to be used when the occlusion occurs on the main patch. As for the previous study, the
proposed technique will be validated acquiring the same trials with both the single camera used in the
proposed markerless technique and a traditional stereophotogrammetric system. This technique is
expected to provide a simple and reliable knee flexion/extension measurement
A hybrid markerless approach for 2D gait analysis: application to gait of children with cerebral palsy
No full textA 2D hybrid markerless technique is proposed to estimate the
lower limb joint kinematics in children with cerebral palsy
(CP). The markerless methodology presented is defined as
hybrid since it uses garments as “segmental markers”,
specifically high-cut underwear which contributes in defining
the pelvis segment and ankle socks for the definition of the
foot segment. Six CP children participated in this study and
five trials were recorded for each subject. The proposed
technique requires the following steps: anthropometric
measurements, video acquisition (Figure a), segmentation
(Figure b), skeletonization (Figure c), thresholding and edge
detection (Figure d), determining intersection points (Figure e)
and fitting reference axes (Figure f). Validation was done by
comparing the lower limb joint kinematics estimated by the
hybrid approach with those obtained using a marker-based
system. The average angular offsets were in the range of 2.9-
4.5 for ankle plantar/dorsi-flexion (α), 0.3-2.1 for knee
flexion/extension (β) and 0.4-2.4 for hip flexion/extension (γ).
The average RMSD results were in the range of 2.8-6.0 for the
(α), 3.9-8.5 (β) and 3.9-7.6 and (γ) angles. RMSD values were
in general within the intra-subject variability. The proposed
technique can be a possible economical alternative for
estimating the lower limb joint kinematics of children with
CP
Musculoskeletal system modelling for the evaluation of motor disability
No full textMusculoskeletal system models aimed at assessing activity limitation and impairment of a specific individual in the domain of mobility are presented. A thorough biomechanical analysis of selected motor tasks would be effective but awkward to apply in clinical practice by reason of the complexity of both instrumentation and experimental protocols. Therefore, different methods are proposed that entail the measurement of a minimum number of biomechanical variables. However, since data thus obtained do not necessarily lend themselves to straightforward interpretation, they are fed to models of the musculoskeletal system that embody the invariant aspects of both the modelled system and the specific motor task (minimum measured-input models). Two different sets of mathematical models are presented that aim at assessing activity limitation and establishing a relationship between this limitation and impairment, respectively
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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