Research Areas:

Artificial Intelligence in Healthcare

Deep learning segmentation of transverse musculoskeletal ultrasound images for neuromuscular disease assessment

Authors:
Francesco Marzola, Nens van Alfen, Jonne Doorduin, Kristen M. Meiburger
Journal:
Computers in Biology and Medicine
DOI:
10.1016/j.compbiomed.2021.104623
Year:
2021
Abstract:

Ultrasound imaging is a patient-friendly and robust technique for studying physiological and pathological muscles. An automatic deep learning (DL) system for the analysis of ultrasound images could be useful to support an expert operator, allowing the study of large datasets requiring less human interaction. The purpose of this study is to present a deep learning algorithm for the cross-sectional area (CSA) segmentation in transverse musculoskeletal ultrasound images, providing a quantitative grayscale analysis which is useful for studying muscles, and to validate the results in a large dataset. The dataset included 3917 images of biceps brachii, tibialis anterior and gastrocnemius medialis acquired on 1283 subjects (mean age 50 ± 21 years, 729 male). The algorithm was based on multiple deep-learning architectures, and its performance was compared to a manual expert segmentation. We compared the mean grayscale value inside the automatic and manual CSA using Bland-Altman plots and a correlation analysis. Classification in healthy and abnormal muscles between automatic and manual segmentation were compared using the grayscale value z-scores. In the test set, a Precision of 0.88 ± 0.12 and a Recall of 0.92 ± 0.09 was achieved. The network segmentation performance was slightly less in abnormal muscles, without a loss of discrimination between healthy and abnormal muscle images. Bland-Altman plots showed no clear trend in the error distribution and the two readings have a 0.99 Pearson’s correlation coefficient (p < 0.001, test set). The ICC(A, 1) calculated between the z-score readings was 0.99. The algorithm achieves robust CSA segmentation performance and gives mean grayscale level information comparable to a manual operator. This could provide a helpful tool for clinicians in neuromuscular disease diagnosis and follow-up. The entire dataset and code are made available for the research community.

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A Convolutional Neural Network based system for Colorectal cancer segmentation on MRI images

Authors:
J. Panic; A. Defeudis; S. Mazzetti; S. Rosati; G. Giannetto; L. Vassallo; D. Regge; G. Balestra; V. Giannini
Journal:
2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC)
DOI:
10.1109/EMBC44109.2020.9175804
Year:
2020
Abstract:

The aim of the study is to present a new Convolutional Neural Network (CNN) based system for the automatic segmentation of the colorectal cancer. The algorithm implemented consists of several steps: a pre-processing to normalize and highlights the tumoral area, the classification based on CNNs, and a post-processing aimed at reducing false positive elements. The classification is performed using three CNNs: each of them classifies the same regions of interest acquired from three different MR sequences. The final segmentation mask is obtained by a majority voting. Performances were evaluated using a semi-automatic segmentation revised by an experienced radiologist as reference standard. The system obtained Dice Similarity Coefficient (DSC) of 0.60, Precision (Pr) of 0.76 and Recall (Re) of 0.55 on the testing set. After applying the leave-one-out validation, we obtained a median DSC=0.58, Pr=0.74, Re=0.54. The promising results obtained by this system, if validated on a larger dataset, could strongly improve personalized medicine.

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Radiomics predicts response of individual HER2-amplified colorectal cancer liver metastases in patients treated with HER2-targeted therapy

Authors:
V. Giannini, S. Rosati, A. Defeudis, G. Balestra, L. Vassallo, G. Cappello, S. Mazzetti, C. De Mattia, F. Rizzetto, A. Torresin, A. Sartore-Bianchi, S. Siena, A. Vanzulli, F. Leone, V. Zagonel, S. Marson
Journal:
International journal of cancer
DOI:
10.1002/ijc.33271
Year:
2020
Abstract:

The aim of our study was to develop and validate a machine learning algorithm to predict response of individual HER2-amplified colorectal cancer liver metastases (lmCRC) undergoing dual HER2-targeted therapy. Twenty-four radiomics features were extracted after 3D manual segmentation of 141 lmCRC on pretreatment portal CT scans of a cohort including 38 HER2-amplified patients; feature selection was then performed using genetic algorithms. lmCRC were classified as nonresponders (R-), if their largest diameter increased more than 10% at a CT scan performed after 3 months of treatment, responders (R+) otherwise. Sensitivity, specificity, negative (NPV) and positive (PPV) predictive values in correctly classifying individual lesion and overall patient response were assessed on a training dataset and then validated on a second dataset using a Gaussian naïve Bayesian classifier. Per-lesion sensitivity, specificity, NPV and PPV were 89%, 85%, 93%, 78% and 90%, 42%, 73%, 71% respectively in the testing and validation datasets. Per-patient sensitivity and specificity were 92% and 86%. Heterogeneous response was observed in 9 of 38 patients (24%). Five of nine patients were carriers of nonresponder lesions correctly classified as such by our radiomics signature, including four of seven harboring only one nonresponder lesion. The developed method has been proven effective in predicting behavior of individual metastases to targeted treatment in a cohort of HER2 amplified patients. The model accurately detects responder lesions and identifies nonresponder lesions in patients with heterogeneous response, potentially paving the way to multimodal treatment in selected patients. Further validation will be needed to confirm our findings.

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Radiomics for Identification of Active Bone Marrow from CT: An Exploratory Study

Authors:
S. Rosati; G. Balestra; P. Franco; C. Fiandra; F. Arcadipane; P. Silvetti; U. Ricardi; E. Gallio
Journal:
2018 IEEE Life Sciences Conference (LSC)
DOI:
10.1109/LSC.2018.8572154
Year:
2018
Abstract:

The radiation dose received by the pelvic Bone Marrow (BM) is a predictive factor for Hematologic Toxicity (HT) occurrence in the treatment of anal cancer. For this reason it is important to avoid BM during radiotherapy. In particular, the standard strategy in these cases consists in the identification of hematopoietically active BM (actBM), i.e. the part of BM in charge of blood cells generation, on 18 FDG-PET, FLT-PET or MRI, but no approached have been developed for identifying actBM from CT images. This exploratory study aims to use radiomics for detecting actBM on CT sequences. Our approach is based on the extraction of 36 first-order and texture (second-order) features for each CT slice. These features are used as input of a Decision Tree (DT) classifier able to discriminate between active and inactive BM regions on the images. This method was applied to five patients affected by carcinoma of the anal canal and the obtained actBM segmentation was compared with the standard actBM identification from 18 FDG-PET (reference standard, RS). Our results show that actBM identification in lumbosacral and iliac structures using radiomics overlaps the RS for more than 75% in 4 out of 5 patients.

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Biomedical Signal And Data Processing

Does texting while walking really affect gait in young adults?

Authors:
V. Agostini, F. Lo Fermo, G. Massazza and M. Knaflitz
Journal:
Journal of NeuroEngineering and Rehabilitation
DOI:
10.1186/s12984-015-0079-4
Year:
2015
Abstract:

Background: Texting on a smartphone while walking has become a customary task among young adults. In recent literature many safety concerns on distracted walking have been raised. It is often hypothesized that the allocation of attentional resources toward a secondary task can influence dynamic stability. In the double task of walking and texting it was found that gait speed is reduced, but there is scarce evidence of a modified motor control strategy compromising stability. The aim of this study is twofold: 1) to comprehensively examine the gait modifications occurring when texting while walking, including the study of the lower limb muscle activation patterns, 2) to specifically assess the co-contraction of ankle antagonist muscles. We hypothesized that texting while walking increases co-contractions of ankle antagonist muscles when the body weight is transferred from one lower limb to the other, to improve the distal motor control and joint stabilization.

Methods: From the gait data collected during an instrumented walk lasting 3 min, we calculated the spatio-temporal parameters, the ankle and knee kinematics, the muscle activation patterns of tibialis anterior, gastrocnemius lateralis, peroneus longus, rectus femoris, and lateral hamstrings, and the co-contraction (occurrence and duration) of the ankle antagonist muscles (tibialis anterior and gastrocnemius lateralis), bilaterally.

Results: Young adults showed, overall, small gait modifications that could be mainly ascribable to gait speed reduction and a modified body posture due to phone handling. We found no significant alterations of ankle and knee kinematics and a slightly delayed activation onset of the left gastrocnemius lateralis. However, we found an increased co-contraction of tibialis anterior and gastrocnemius lateralis, especially during mid-stance. Conversely, we found a reduced co-contraction during terminal stance.

Conclusions: Our results suggest that, in young adults, there is an adjustment of the motor control strategy aimed at increasing ankle joint stability in a specific and “critical” phase of the gait cycle, when the body weight is transferred from one leg to the other.

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Instrumented Gait Analysis for an Objective Pre-/Postassessment of Tap Test in Normal Pressure Hydrocephalus

Authors:
V. Agostini, M. Lanotte, M. Carlone, M. Campagnoli, I. Azzolin, R. Scarafia, G. Massazza, M. Knaflitz
Journal:
Archives of Physical Medicine and Rehabilitation
DOI:
10.1016/j.apmr.2015.02.014
Year:
2015
Abstract:

Objective

To present an objective method to evaluate gait improvements after a tap test in idiopathic normal pressure hydrocephalus (INPH).

Design

Retrospective analysis of gait data.

Setting

Public tertiary care center, day hospital. The gait analysis was performed before and 2 to 4 hours after the tap test.

Participants

Participants included patients with INPH (n=60) and age- and sex-matched controls (n=50; used to obtain reference intervals). From an initial referred sample of 79 patients (N=79), we excluded those unable to walk without walking aids (n=9) and those with incomplete (pre-/posttap test) gait data (n=10). Thirteen out of 60 patients were shunted and then reappraised after 6 months.

Interventions

Not applicable.

Main Outcome Measures

Mahalanobis distance from controls, before and after the tap test. Eleven gait parameters were combined in a single quantitative score. Walking velocity was also evaluated because it is frequently used in tap test assessment.

Results

Patients were classified into 2 groups: tap test responders (n=22, 9 of them were shunted) and not suitable for shunt (n=38, 4 of them were shunted). In the tap test responders group, 9 out of 9 patients improved after shunt. In the not suitable for shunt group, 3 out of 4 patients did not improve. Gait velocity increased after the tap test in 53% of responders and in 37% of patients not suitable for shunt.

Conclusions

The new method is applicable to clinical practice and allows for selecting tap test responders in an objective way, quantifying the improvements. Our results suggest that gait velocity alone is not sufficient to reliably assess tap test effects.

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Clinical Process Modelling

Agent-Based Modeling and Simulation of Care Delivery for Patients with Thrombotic and Bleeding Disorders

Authors:
N. Giordano, S. Rosati, F. Valeri, A. Borchiellini, G. Balestra
Journal:
STUDIES IN HEALTH TECHNOLOGY AND INFORMATICS, MIE 2020
DOI:
10.3233/SHTI200358
Year:
2020
Abstract:

The quality of patients care delivery is thought to be strongly affected by the physicians’ workload. In this study we present an Agent-Based model of the processes during a typical working day. We simulated the current scenario and a possible scenario concerning the introduction of a second ambulatory as a potential improvement in the center organization. Our results validated the reliability of the model and showed that the introduction of a second ambulatory averagely reduces the daily physician’ workload.

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An Approach Based on Process Modeling for Implementing a Health Information Technology in Clinical Practice

Authors:
G.M. Zaccaria; S. Rosati; M. Zema; V. Agostini; G. Balestra
Journal:
Journal of Medical Imaging and Health Informatics
DOI:
10.1166/jmihi.2018.2353
Year:
2018
Abstract:

The introduction of a new Health Information Technology (HIT) in a healthcare context is a very complex process. The aim of this study is to propose a completely original approach for the implementation a new HIT in a healthcare facility or department. This novel approach is made of four steps and based on process modeling. The first step is the identification of all the stakeholders involved. The second step consists in performing a detailed description of all clinical and administrative processes that will use the new HIT in order to understand how people, resources and documents interact among them. The third step allows the analysis of the HIT functionalities in order to highlight potential problems or risks that could emerge during its daily usage and guarantee its interoperability with other software. The fourth step concerns the construction of an adoption plan, in order to avoiding sharp transitions. A set of tools were associated to each step to guarantee a correct design and implementation. An application concerning the implementation of a new commercial HIT for Computerized Provider Order Entry (CPOE) in the oncology department of a large Italian hospital is reported as an example of the proposed approach. Furthermore, the user satisfaction about the introduction of the new CPOE in the oncology department was evaluated by means of a set of questionnaires. A positive evaluation of the process emerged from this analysis, confirming the goodness of the proposed approach. Moreover, the questionnaires results showed a high level of user satisfaction.

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Characterization of Physicians Workload in a Reference Center for the Treatment of Thrombotic and Bleeding Disorders

Authors:
S. Rosati; F. Valeri; A. Borchiellini; C. M. Gianfreda; G. Balestra
Journal:
2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
DOI:
10.1109/EMBC.2019.8856820
Year:
2019
Abstract:

Heavy workloads in healthcare have been often associated to adverse clinical outcomes. To reduce workloads, an optimal scheduling of clinical staff resources is not enough, but particular attention must be payed to work organization and task characteristics. Moreover, interruptions during the clinical practice contribute to increase perceived workloads. In this study we analyzed and characterized the physicians’ workload in an Italian center for the treatment of thrombotic and bleeding disorders. First, all clinical and administrative processes performed in the center were analyzed by means of two process modelling tools. Then, the quantification of the physicians’ workload and the characterization of interruptions during practice were conducted. From our results it emerged that the task that mainly impacts on the workload is ambulatory care (42% of total workload) while interruptions produce a delay of almost 15 minutes per day and mainly occur during visits. Including all activities, the total daily workload per physician was 8 hours on average. In this time breaks were not taken into account. Concluding, from our analysis it is evident that the physicians’ workload in the analyzed center is heavy and interruptions represent a source of delay in the workflow, that impact the physicians’ workload.

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Developing medical device software in compliance with regulations

Authors:
M. Zema; S. Rosati; V. Gioia; M. Knaflitz; G. Balestra
Journal:
2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
DOI:
10.1109/EMBC.2015.7318614
Year:
2015
Abstract:

In the last decade, the use of information technology (IT) in healthcare has taken a growing role. In fact, the adoption of an increasing number of computer tools has led to several benefits related to the process of patient care and allowed easier access to social and health care resources. At the same time this trend gave rise to new challenges related to the implementation of these new technologies. Software used in healthcare can be classified as medical devices depending on the way they are used and on their functional characteristics. If they are classified as medical devices they must satisfy specific regulations. The aim of this work is to present a software development framework that can allow the production of safe and high quality medical device software and to highlight the correspondence between each software development phase and the appropriate standard and/or regulation.

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Modelling and analysis of four telemedicine Italian experiences

Authors:
S. Rosati; M. Zema; C. Castagneri; F. Marchetti; G. Balestra
Journal:
2017 39th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
DOI:
10.1109/EMBC.2017.8037398
Year:
2017
Abstract:

In the last 10 years the European population aged 65 years and over grew of 2.3%, with Italy having the highest share of elderly persons in the total population. OPLON (OPportunities for active and healthy LONgevity) is a project supported by the Italian Ministry of Education, Universities, and Research aiming to identify and prevent frailty and to improve the life quality of elderly subjects. The main goal of OPLON is to develop a “Care&Cure” model for the management of subjects with different morbidities and co-morbidities, adaptable to the subject’s risk level and to the regional contexts. In this study we analyzed four Italian telemedicine experiences addressed to chronic, geriatric or partially self-sufficient subjects. Each of them was exhaustively described by means of three process modelling tools (synopsis, workflow and swimlane activity diagrams). Starting from this analysis, we defined a general model of tele-monitoring and tele-assistance of frail and pre-frail people with different needs and pathologies. The proposed model was characterized by three macro processes (enrollment, assessment and assistance) and four groups of actors (patient, general practitioner/specialist physician, multidisciplinary team, and healthcare professionals). Combining this model with a detailed analysis of regulations and legislations in force both at local and national level, it will be possible to design the complete and efficient “Care&Cure” model.

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Design of Biomedical Instrumentation

A wearable device to assess postural sway

Authors:
V. Agostini, E. Aiello, D. Fortunato, M. Knaflitz, and L. Gastaldi
Journal:
2019 IEEE 23rd International Symposium on Consumer Technologies (ISCT)
DOI:
10.1109/ISCE.2019.8901019
Year:
2019
Abstract:

The maintenance of balance in upright stance is traditionally evaluated using heavy and expensive force platforms. The aim of this work is to prove the usefulness of a low-cost wearable sensor (an actigraph) to assess postural sway. We compared the performance of the device to a gold standard force platform. We analyzed measurements of postural sway in four conditions differently challenging the subject: with eyes open or closed, while keeping a small or large base of support. We estimated the main postural parameters (ellipse area, mediolateral and antero-posterior root-mean square, eccentricity, sway path length) considering: 1) acceleration data recorded by the actigraph, and 2) traditional COP data obtained from the force platform. We found that it is possible to clearly distinguish the differences among the postural parameters, obtained in the various balance conditions, also using acceleration data. Our results show that the wearable device allows for obtaining information similar to those achievable by the force platform. This support the use of wearable devices to assess postural balance, in a handy and cheap manner.

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Human Motion Analysis

Atypical Gait Cycles in Parkinson’s Disease

Authors:
M. Ghislieri, V. Agostini, L. Rizzi, M. Knaflitz, and M. Lanotte
Journal:
Sensors
DOI:
10.3390/s21155079
Year:
2021
Abstract:

It is important to find objective biomarkers for evaluating gait in Parkinson’s Disease (PD), especially related to the foot and lower leg segments. Foot-switch signals, analyzed through Statistical Gait Analysis (SGA), allow the foot-floor contact sequence to be characterized during a walking session lasting five-minutes, which includes turnings. Gait parameters were compared between 20 PD patients and 20 age-matched controls. PDs showed similar straight-line speed, cadence, and double-support compared to controls, as well as typical gait-phase durations, except for a small decrease in the flat-foot contact duration (−4% of the gait cycle, p = 0.04). However, they showed a significant increase in atypical gait cycles (+42%, p = 0.006), during both walking straight and turning. A forefoot strike, instead of a “normal” heel strike, characterized the large majority of PD’s atypical cycles, whose total percentage was 25.4% on the most-affected and 15.5% on the least-affected side. Moreover, we found a strong correlation between the atypical cycles and the motor clinical score UPDRS-III (r = 0.91, p = 0.002), in the subset of PD patients showing an abnormal number of atypical cycles, while we found a moderate correlation (r = 0.60, p = 0.005), considering the whole PD population. Atypical cycles have proved to be a valid biomarker to quantify subtle gait dysfunctions in PD patients

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An Algorithm for Choosing the Optimal Number of Muscle Synergies during Walking

Authors:
R. Ballarini, M. Ghislieri, M. Knaflitz and V. Agostini
Journal:
Sensors
DOI:
10.3390/s21103311
Year:
2021
Abstract:

In motor control studies, the 90% thresholding of variance accounted for (VAF) is the classical way of selecting the number of muscle synergies expressed during a motor task. However, the adoption of an arbitrary cut-off has evident drawbacks. The aim of this work is to describe and validate an algorithm for choosing the optimal number of muscle synergies (ChoOSyn), which can overcome the limitations of VAF-based methods. The proposed algorithm is built considering the following principles: (1) muscle synergies should be highly consistent during the various motor task epochs (i.e., remaining stable in time), (2) muscle synergies should constitute a base with low intra-level similarity (i.e., to obtain information-rich synergies, avoiding redundancy). The algorithm performances were evaluated against traditional approaches (threshold-VAF at 90% and 95%, elbow-VAF and plateau-VAF), using both a simulated dataset and a real dataset of 20 subjects. The performance evaluation was carried out by analyzing muscle synergies extracted from surface electromyographic (sEMG) signals collected during walking tasks lasting 5 min. On the simulated dataset, ChoOSyn showed comparable performances compared to VAF-based methods, while, in the real dataset, it clearly outperformed the other methods, in terms of the fraction of correct classifications, mean error (ME), and root mean square error (RMSE). The proposed approach may be beneficial to standardize the selection of the number of muscle synergies between different research laboratories, independent of arbitrary thresholds

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Muscle synergies extracted using principal activations: improvement of robustness and interpretability

Authors:
M. Ghislieri, V. Agostini, and M. Knaflitz
Journal:
IEEE Transactions on Neural Systems and Rehabilitation Engineering
DOI:
10.1109/TNSRE.2020.2965179
Year:
2020
Abstract:

The muscle synergy theory has been widely used to assess the modular organization of the central nervous system (CNS) during human locomotion. The pre-processing approach applied to the surface electromyographic (sEMG) signals influences the extraction of muscle synergies. The aim of this contribution is to assess the improvements in muscle synergy extraction obtained by using an innovative pre-processing approach. We evaluate the improvement in terms of the possible variation in the number of muscle synergies, of the intra-subject consistency, of the robustness, and of the interpretability of the results. The pre-processing approach presented in this paper is based on the extraction of the muscle principal activations (muscle activations strictly necessary to accomplish a specific biomechanical task) from the original sEMG signals, to then obtain muscle synergies using principal activations only. The results herein presented show that the application of this novel approach for the extraction of the muscle synergies provides a more robust and easily interpretable description of the modular organization of the CNS with respect to the standard pre-processing approach.

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Muscle Synergy Assessment During Single-Leg Stance

Authors:
M. Ghislieri, M. Knaflitz, L. Labanca, G. Barone, L. Bragonzoni, M. G. Benedetti, and V. Agostini
Journal:
IEEE Transactions on Neural Systems and Rehabilitation Engineering
DOI:
10.1109/TNSRE.2020.3030847
Year:
2020
Abstract:

In the study of muscle synergies during the maintenance of single-leg stance there are several methodological issues that must be taken into account before muscle synergy extraction. In particular, it is important to distinguish between epochs of surface electromyography (sEMG) signals corresponding to “well-balanced” and “unbalanced” single-leg stance, since different motor control strategies could be used to maintain balance. The aim of this work is to present and define a robust procedure to distinguish between “well-balanced” and “unbalanced” single-leg stance to be chosen as input for the algorithm used to extract muscle synergies. Our results demonstrate that the proposed approach for the selection of sEMG epochs relative to “well-balanced” and “unbalanced” single-leg stance is robust with respect to the selection of the segmentation threshold, revealing a high consistency in the number of muscle synergies and high similarity among the weight vectors (correlation values range from 0.75 to 0.97). Moreover, differences in terms of average recruitment levels and balance control strategies were detected, suggesting a slightly different modular organization between “well-balanced” and “unbalanced” single-leg stance. In conclusion, this approach can be successfully used as a pre-processing step before muscle synergy extraction, allowing for a better assessment of motor control strategies during the single-leg stance task.

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How to improve robustness in muscle synergy extraction

Authors:
M. Ghislieri, V. Agostini, and M. Knaflitz
Journal:
2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
DOI:
10.1109/EMBC.2019.8856438
Year:
2019
Abstract:

The muscle synergy theory was widely used in literature to assess the modular organization of the central nervous system (CNS) during human locomotion. The extraction of muscle synergies may be strongly influenced by the preprocessing techniques applied to surface electromyographic (sEMG) signals. The aim of this contribution is to assess the robustness improvement in muscle synergy extraction obtained using an innovative pre-processing technique with respect to the standard procedure. The new pre-processing technique that we propose is based on the extraction of principal muscle activation intervals (necessary to accomplish a specific biomechanical task during gait) from the original sEMG signals, discarding the secondary muscle activation intervals (activations that occur only in some strides with auxiliary functions). Results suggest that the extraction of the principal activation intervals from sEMG provide a more consistent and stable description of the modular organization of the CNS with respect to the standard pre-processing procedure.

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The Effect of Signal-to-Noise Ratio on Muscle Synergy Extraction

Authors:
M. Ghislieri, V. Agostini, and M. Knaflitz
Journal:
2018 IEEE Life Sciences Conference (LSC)
DOI:
10.1109/LSC.2018.8572075
Year:
2018
Abstract:

The modular organization of the central nervous system (CNS) during motor tasks was widely assessed by means of muscle synergies. The aim of this work was to assess the impact of the Signal-to-Noise Ratio (SNR) on muscle synergies extracted from synthetic surface electromyographic (sEMG) signals that simulate the muscle activity of the lower limb during walking. To evaluate the effect of the SNR, the similarity between the weights vectors and the activation coefficients extracted from real sEMG signals and from simulated sEMG signals at different values of SNR was computed. Results reveal that muscle synergy extraction is strongly dependent upon the quality of the sEMG signals simulated.

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The role of central vision in posture: Postural sway adaptations in Stargardt patients

Authors:
V. Agostini, A. Sbrollini, C. Cavallini, A. Busso, G. Pignata and M. Knaflitz
Journal:
Gait & Posture
DOI:
10.1016/j.gaitpost.2015.10.003
Year:
2016
Abstract:

The role of central and peripheral vision in the maintenance of upright stance is debated in literature. Stargardt disease causes visual deficits affecting the central field, but leaving unaltered a patient’s peripheral vision. Hence, the study of this rare pathology gives the opportunity to selectively investigate the role of central vision in posture. Postural sway in quiet stance was analyzed in 10 Stargardt patients and 10 control subjects, in three different conditions: (1) eyes closed, (2) eyes open, gazing at a fixed target, and (3) eyes open, tracking a moving target. Stargardt patients outperformed controls in the condition with eyes closed, showing a reduced root mean square (RMS) of the medio-lateral COP displacement, while their performance was not significantly different from controls in the antero-posterior direction. There were no significant differences between patients and controls in open eyes conditions. These results suggest that Stargardt patients adapted to a different visual-somatosensory integration, relying less on vision, especially in the medio-lateral direction. Hence, the central vision seems to affect mostly the medio-lateral direction of postural sway. This finding supports the plausibility of the “functional sensitivity hypothesis”, that assigns complementary roles to central and peripheral vision in the control of posture.

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Does texting while walking really affect gait in young adults?

Authors:
V. Agostini, F. Lo Fermo, G. Massazza and M. Knaflitz
Journal:
Journal of NeuroEngineering and Rehabilitation
DOI:
10.1186/s12984-015-0079-4
Year:
2015
Abstract:

Background: Texting on a smartphone while walking has become a customary task among young adults. In recent literature many safety concerns on distracted walking have been raised. It is often hypothesized that the allocation of attentional resources toward a secondary task can influence dynamic stability. In the double task of walking and texting it was found that gait speed is reduced, but there is scarce evidence of a modified motor control strategy compromising stability. The aim of this study is twofold: 1) to comprehensively examine the gait modifications occurring when texting while walking, including the study of the lower limb muscle activation patterns, 2) to specifically assess the co-contraction of ankle antagonist muscles. We hypothesized that texting while walking increases co-contractions of ankle antagonist muscles when the body weight is transferred from one lower limb to the other, to improve the distal motor control and joint stabilization.

Methods: From the gait data collected during an instrumented walk lasting 3 min, we calculated the spatio-temporal parameters, the ankle and knee kinematics, the muscle activation patterns of tibialis anterior, gastrocnemius lateralis, peroneus longus, rectus femoris, and lateral hamstrings, and the co-contraction (occurrence and duration) of the ankle antagonist muscles (tibialis anterior and gastrocnemius lateralis), bilaterally.

Results: Young adults showed, overall, small gait modifications that could be mainly ascribable to gait speed reduction and a modified body posture due to phone handling. We found no significant alterations of ankle and knee kinematics and a slightly delayed activation onset of the left gastrocnemius lateralis. However, we found an increased co-contraction of tibialis anterior and gastrocnemius lateralis, especially during mid-stance. Conversely, we found a reduced co-contraction during terminal stance.

Conclusions: Our results suggest that, in young adults, there is an adjustment of the motor control strategy aimed at increasing ankle joint stability in a specific and “critical” phase of the gait cycle, when the body weight is transferred from one leg to the other.

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Instrumented Gait Analysis for an Objective Pre-/Postassessment of Tap Test in Normal Pressure Hydrocephalus

Authors:
V. Agostini, M. Lanotte, M. Carlone, M. Campagnoli, I. Azzolin, R. Scarafia, G. Massazza, M. Knaflitz
Journal:
Archives of Physical Medicine and Rehabilitation
DOI:
10.1016/j.apmr.2015.02.014
Year:
2015
Abstract:

Objective

To present an objective method to evaluate gait improvements after a tap test in idiopathic normal pressure hydrocephalus (INPH).

Design

Retrospective analysis of gait data.

Setting

Public tertiary care center, day hospital. The gait analysis was performed before and 2 to 4 hours after the tap test.

Participants

Participants included patients with INPH (n=60) and age- and sex-matched controls (n=50; used to obtain reference intervals). From an initial referred sample of 79 patients (N=79), we excluded those unable to walk without walking aids (n=9) and those with incomplete (pre-/posttap test) gait data (n=10). Thirteen out of 60 patients were shunted and then reappraised after 6 months.

Interventions

Not applicable.

Main Outcome Measures

Mahalanobis distance from controls, before and after the tap test. Eleven gait parameters were combined in a single quantitative score. Walking velocity was also evaluated because it is frequently used in tap test assessment.

Results

Patients were classified into 2 groups: tap test responders (n=22, 9 of them were shunted) and not suitable for shunt (n=38, 4 of them were shunted). In the tap test responders group, 9 out of 9 patients improved after shunt. In the not suitable for shunt group, 3 out of 4 patients did not improve. Gait velocity increased after the tap test in 53% of responders and in 37% of patients not suitable for shunt.

Conclusions

The new method is applicable to clinical practice and allows for selecting tap test responders in an objective way, quantifying the improvements. Our results suggest that gait velocity alone is not sufficient to reliably assess tap test effects.

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Postural sway in volleyball players

Authors:
V. Agostini, E. Chiaramello, L. Canavese, C. Bredariol and M. Knaflitz
Journal:
Human Movement Science
DOI:
10.1016/j.humov.2013.01.002
Year:
2013
Abstract:

The aim of this work was to analyze the postural sway of volleyball players in bipedal quiet stance. The center of pressure (CoP) was measured in 46 athletes and 42 non-athlete controls. Each subject was tested in 10 different conditions, 5 with their eyes open and 5 with their eyes closed. Volleyball players showed greater CoP ellipses, suggesting a different model of sensory integration in their postural stability. A multivariate approach to data analysis demonstrated that the postural sway of the two groups was different when the subjects kept their eyes open, but it was not with visual deprivation. This could partially be explained by the better ‘dynamic’ visual acuity of athletes, since possible (‘static’) refractive errors were corrected for both groups. Furthermore, we expected that national players, engaged in more intensive training programs, were more different from controls than regional ones, and that defensive players, whose role requires the quickest reaction times, were more different from controls than hitters. Our results confirmed these hypothesis. The protocol presented might be useful to assess the efficacy of intensive sport training programs and/or to select elite players with an aptitude for a specific playing position.

Read more

Postural control after traumatic brain injury in patients with neuro-ophthalmic deficits

Authors:
V. Agostini, E. Chiaramello, C. Bredariol, C. Cavallini and M. Knaflitz
Journal:
Gait & Posture
DOI:
10.1016/j.gaitpost.2011.05.008
Year:
2011
Abstract:

Postural instability is a common and devastating consequence of traumatic brain injury (TBI). The majority of TBI patients also suffer from neuro-ophthalmic deficits that can be an important contributing element to their sensation of vertigo and dizziness. Static posturography aims at the objective evaluation of patient balance impairment, but is usually affected by large inter- and intra-subject variability. Here we propose a protocol based on 10 randomized trials stimulating in different ways the visual and vestibular systems. Due to its completeness, our protocol highlights the specific residual difficulties of each patient in the various conditions. In this way, it was possible to evidence significant balance abnormalities in TBI patients with respect to controls. Moreover, by means of a multivariate analysis we were able to discriminate different levels of residual neuro-ophthalmic impairment.

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Medical Device Software

An Approach Based on Process Modeling for Implementing a Health Information Technology in Clinical Practice

Authors:
G.M. Zaccaria; S. Rosati; M. Zema; V. Agostini; G. Balestra
Journal:
Journal of Medical Imaging and Health Informatics
DOI:
10.1166/jmihi.2018.2353
Year:
2018
Abstract:

The introduction of a new Health Information Technology (HIT) in a healthcare context is a very complex process. The aim of this study is to propose a completely original approach for the implementation a new HIT in a healthcare facility or department. This novel approach is made of four steps and based on process modeling. The first step is the identification of all the stakeholders involved. The second step consists in performing a detailed description of all clinical and administrative processes that will use the new HIT in order to understand how people, resources and documents interact among them. The third step allows the analysis of the HIT functionalities in order to highlight potential problems or risks that could emerge during its daily usage and guarantee its interoperability with other software. The fourth step concerns the construction of an adoption plan, in order to avoiding sharp transitions. A set of tools were associated to each step to guarantee a correct design and implementation. An application concerning the implementation of a new commercial HIT for Computerized Provider Order Entry (CPOE) in the oncology department of a large Italian hospital is reported as an example of the proposed approach. Furthermore, the user satisfaction about the introduction of the new CPOE in the oncology department was evaluated by means of a set of questionnaires. A positive evaluation of the process emerged from this analysis, confirming the goodness of the proposed approach. Moreover, the questionnaires results showed a high level of user satisfaction.

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Developing medical device software in compliance with regulations

Authors:
M. Zema; S. Rosati; V. Gioia; M. Knaflitz; G. Balestra
Journal:
2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
DOI:
10.1109/EMBC.2015.7318614
Year:
2015
Abstract:

In the last decade, the use of information technology (IT) in healthcare has taken a growing role. In fact, the adoption of an increasing number of computer tools has led to several benefits related to the process of patient care and allowed easier access to social and health care resources. At the same time this trend gave rise to new challenges related to the implementation of these new technologies. Software used in healthcare can be classified as medical devices depending on the way they are used and on their functional characteristics. If they are classified as medical devices they must satisfy specific regulations. The aim of this work is to present a software development framework that can allow the production of safe and high quality medical device software and to highlight the correspondence between each software development phase and the appropriate standard and/or regulation.

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Modelling and analysis of four telemedicine Italian experiences

Authors:
S. Rosati; M. Zema; C. Castagneri; F. Marchetti; G. Balestra
Journal:
2017 39th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
DOI:
10.1109/EMBC.2017.8037398
Year:
2017
Abstract:

In the last 10 years the European population aged 65 years and over grew of 2.3%, with Italy having the highest share of elderly persons in the total population. OPLON (OPportunities for active and healthy LONgevity) is a project supported by the Italian Ministry of Education, Universities, and Research aiming to identify and prevent frailty and to improve the life quality of elderly subjects. The main goal of OPLON is to develop a “Care&Cure” model for the management of subjects with different morbidities and co-morbidities, adaptable to the subject’s risk level and to the regional contexts. In this study we analyzed four Italian telemedicine experiences addressed to chronic, geriatric or partially self-sufficient subjects. Each of them was exhaustively described by means of three process modelling tools (synopsis, workflow and swimlane activity diagrams). Starting from this analysis, we defined a general model of tele-monitoring and tele-assistance of frail and pre-frail people with different needs and pathologies. The proposed model was characterized by three macro processes (enrollment, assessment and assistance) and four groups of actors (patient, general practitioner/specialist physician, multidisciplinary team, and healthcare professionals). Combining this model with a detailed analysis of regulations and legislations in force both at local and national level, it will be possible to design the complete and efficient “Care&Cure” model.

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Medical Image Analysis Using Innovative Intelligent Systems

Carotid Ultrasound Boundary Study (CUBS): An Open Multicenter Analysis of Computerized Intima–Media Thickness Measurement Systems and Their Clinical Impact

Authors:
Kristen M.Meiburger, Guillaume Zahnd, Francesco Faita, Christos P. Loizou, Catarina Carvalho, David A. Steinman, Lorenzo Gibello, Rosa Maria Bruno, Francesco Marzola, Ricarda Clarenbach, Martina Francesconi, Andrew N. Nicolaides, Aurelio Campilho, Reza Gh
Journal:
Ultrasound in Medicine and Biology
DOI:
10.1016/j.ultrasmedbio.2021.03.022
Year:
2021
Abstract:

Common carotid intima–media thickness (CIMT) is a commonly used marker for atherosclerosis and is often computed in carotid ultrasound images. An analysis of different computerized techniques for CIMT measurement and their clinical impacts on the same patient data set is lacking. Here we compared and assessed five computerized CIMT algorithms against three expert analysts’ manual measurements on a data set of 1088 patients from two centers. Inter- and intra-observer variability was assessed, and the computerized CIMT values were compared with those manually obtained. The CIMT measurements were used to assess the correlation with clinical parameters, cardiovascular event prediction through a generalized linear model and the Kaplan–Meier hazard ratio. CIMT measurements obtained with a skilled analyst’s segmentation and the computerized segmentation were comparable in statistical analyses, suggesting they can be used interchangeably for CIMT quantification and clinical outcome investigation. To facilitate future studies, the entire data set used is made publicly available for the community at http://dx.doi.org/10.17632/fpv535fss7.1.

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Deep learning segmentation of transverse musculoskeletal ultrasound images for neuromuscular disease assessment

Authors:
Francesco Marzola, Nens van Alfen, Jonne Doorduin, Kristen M. Meiburger
Journal:
Computers in Biology and Medicine
DOI:
10.1016/j.compbiomed.2021.104623
Year:
2021
Abstract:

Ultrasound imaging is a patient-friendly and robust technique for studying physiological and pathological muscles. An automatic deep learning (DL) system for the analysis of ultrasound images could be useful to support an expert operator, allowing the study of large datasets requiring less human interaction. The purpose of this study is to present a deep learning algorithm for the cross-sectional area (CSA) segmentation in transverse musculoskeletal ultrasound images, providing a quantitative grayscale analysis which is useful for studying muscles, and to validate the results in a large dataset. The dataset included 3917 images of biceps brachii, tibialis anterior and gastrocnemius medialis acquired on 1283 subjects (mean age 50 ± 21 years, 729 male). The algorithm was based on multiple deep-learning architectures, and its performance was compared to a manual expert segmentation. We compared the mean grayscale value inside the automatic and manual CSA using Bland-Altman plots and a correlation analysis. Classification in healthy and abnormal muscles between automatic and manual segmentation were compared using the grayscale value z-scores. In the test set, a Precision of 0.88 ± 0.12 and a Recall of 0.92 ± 0.09 was achieved. The network segmentation performance was slightly less in abnormal muscles, without a loss of discrimination between healthy and abnormal muscle images. Bland-Altman plots showed no clear trend in the error distribution and the two readings have a 0.99 Pearson’s correlation coefficient (p < 0.001, test set). The ICC(A, 1) calculated between the z-score readings was 0.99. The algorithm achieves robust CSA segmentation performance and gives mean grayscale level information comparable to a manual operator. This could provide a helpful tool for clinicians in neuromuscular disease diagnosis and follow-up. The entire dataset and code are made available for the research community.

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A Convolutional Neural Network based system for Colorectal cancer segmentation on MRI images

Authors:
J. Panic; A. Defeudis; S. Mazzetti; S. Rosati; G. Giannetto; L. Vassallo; D. Regge; G. Balestra; V. Giannini
Journal:
2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC)
DOI:
10.1109/EMBC44109.2020.9175804
Year:
2020
Abstract:

The aim of the study is to present a new Convolutional Neural Network (CNN) based system for the automatic segmentation of the colorectal cancer. The algorithm implemented consists of several steps: a pre-processing to normalize and highlights the tumoral area, the classification based on CNNs, and a post-processing aimed at reducing false positive elements. The classification is performed using three CNNs: each of them classifies the same regions of interest acquired from three different MR sequences. The final segmentation mask is obtained by a majority voting. Performances were evaluated using a semi-automatic segmentation revised by an experienced radiologist as reference standard. The system obtained Dice Similarity Coefficient (DSC) of 0.60, Precision (Pr) of 0.76 and Recall (Re) of 0.55 on the testing set. After applying the leave-one-out validation, we obtained a median DSC=0.58, Pr=0.74, Re=0.54. The promising results obtained by this system, if validated on a larger dataset, could strongly improve personalized medicine.

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Radiomics predicts response of individual HER2-amplified colorectal cancer liver metastases in patients treated with HER2-targeted therapy

Authors:
V. Giannini, S. Rosati, A. Defeudis, G. Balestra, L. Vassallo, G. Cappello, S. Mazzetti, C. De Mattia, F. Rizzetto, A. Torresin, A. Sartore-Bianchi, S. Siena, A. Vanzulli, F. Leone, V. Zagonel, S. Marson
Journal:
International journal of cancer
DOI:
10.1002/ijc.33271
Year:
2020
Abstract:

The aim of our study was to develop and validate a machine learning algorithm to predict response of individual HER2-amplified colorectal cancer liver metastases (lmCRC) undergoing dual HER2-targeted therapy. Twenty-four radiomics features were extracted after 3D manual segmentation of 141 lmCRC on pretreatment portal CT scans of a cohort including 38 HER2-amplified patients; feature selection was then performed using genetic algorithms. lmCRC were classified as nonresponders (R-), if their largest diameter increased more than 10% at a CT scan performed after 3 months of treatment, responders (R+) otherwise. Sensitivity, specificity, negative (NPV) and positive (PPV) predictive values in correctly classifying individual lesion and overall patient response were assessed on a training dataset and then validated on a second dataset using a Gaussian naïve Bayesian classifier. Per-lesion sensitivity, specificity, NPV and PPV were 89%, 85%, 93%, 78% and 90%, 42%, 73%, 71% respectively in the testing and validation datasets. Per-patient sensitivity and specificity were 92% and 86%. Heterogeneous response was observed in 9 of 38 patients (24%). Five of nine patients were carriers of nonresponder lesions correctly classified as such by our radiomics signature, including four of seven harboring only one nonresponder lesion. The developed method has been proven effective in predicting behavior of individual metastases to targeted treatment in a cohort of HER2 amplified patients. The model accurately detects responder lesions and identifies nonresponder lesions in patients with heterogeneous response, potentially paving the way to multimodal treatment in selected patients. Further validation will be needed to confirm our findings.

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Radiomics for Identification of Active Bone Marrow from CT: An Exploratory Study

Authors:
S. Rosati; G. Balestra; P. Franco; C. Fiandra; F. Arcadipane; P. Silvetti; U. Ricardi; E. Gallio
Journal:
2018 IEEE Life Sciences Conference (LSC)
DOI:
10.1109/LSC.2018.8572154
Year:
2018
Abstract:

The radiation dose received by the pelvic Bone Marrow (BM) is a predictive factor for Hematologic Toxicity (HT) occurrence in the treatment of anal cancer. For this reason it is important to avoid BM during radiotherapy. In particular, the standard strategy in these cases consists in the identification of hematopoietically active BM (actBM), i.e. the part of BM in charge of blood cells generation, on 18 FDG-PET, FLT-PET or MRI, but no approached have been developed for identifying actBM from CT images. This exploratory study aims to use radiomics for detecting actBM on CT sequences. Our approach is based on the extraction of 36 first-order and texture (second-order) features for each CT slice. These features are used as input of a Decision Tree (DT) classifier able to discriminate between active and inactive BM regions on the images. This method was applied to five patients affected by carcinoma of the anal canal and the obtained actBM segmentation was compared with the standard actBM identification from 18 FDG-PET (reference standard, RS). Our results show that actBM identification in lumbosacral and iliac structures using radiomics overlaps the RS for more than 75% in 4 out of 5 patients.

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Neuroengineering

Atypical Gait Cycles in Parkinson’s Disease

Authors:
M. Ghislieri, V. Agostini, L. Rizzi, M. Knaflitz, and M. Lanotte
Journal:
Sensors
DOI:
10.3390/s21155079
Year:
2021
Abstract:

It is important to find objective biomarkers for evaluating gait in Parkinson’s Disease (PD), especially related to the foot and lower leg segments. Foot-switch signals, analyzed through Statistical Gait Analysis (SGA), allow the foot-floor contact sequence to be characterized during a walking session lasting five-minutes, which includes turnings. Gait parameters were compared between 20 PD patients and 20 age-matched controls. PDs showed similar straight-line speed, cadence, and double-support compared to controls, as well as typical gait-phase durations, except for a small decrease in the flat-foot contact duration (−4% of the gait cycle, p = 0.04). However, they showed a significant increase in atypical gait cycles (+42%, p = 0.006), during both walking straight and turning. A forefoot strike, instead of a “normal” heel strike, characterized the large majority of PD’s atypical cycles, whose total percentage was 25.4% on the most-affected and 15.5% on the least-affected side. Moreover, we found a strong correlation between the atypical cycles and the motor clinical score UPDRS-III (r = 0.91, p = 0.002), in the subset of PD patients showing an abnormal number of atypical cycles, while we found a moderate correlation (r = 0.60, p = 0.005), considering the whole PD population. Atypical cycles have proved to be a valid biomarker to quantify subtle gait dysfunctions in PD patients

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An Algorithm for Choosing the Optimal Number of Muscle Synergies during Walking

Authors:
R. Ballarini, M. Ghislieri, M. Knaflitz and V. Agostini
Journal:
Sensors
DOI:
10.3390/s21103311
Year:
2021
Abstract:

In motor control studies, the 90% thresholding of variance accounted for (VAF) is the classical way of selecting the number of muscle synergies expressed during a motor task. However, the adoption of an arbitrary cut-off has evident drawbacks. The aim of this work is to describe and validate an algorithm for choosing the optimal number of muscle synergies (ChoOSyn), which can overcome the limitations of VAF-based methods. The proposed algorithm is built considering the following principles: (1) muscle synergies should be highly consistent during the various motor task epochs (i.e., remaining stable in time), (2) muscle synergies should constitute a base with low intra-level similarity (i.e., to obtain information-rich synergies, avoiding redundancy). The algorithm performances were evaluated against traditional approaches (threshold-VAF at 90% and 95%, elbow-VAF and plateau-VAF), using both a simulated dataset and a real dataset of 20 subjects. The performance evaluation was carried out by analyzing muscle synergies extracted from surface electromyographic (sEMG) signals collected during walking tasks lasting 5 min. On the simulated dataset, ChoOSyn showed comparable performances compared to VAF-based methods, while, in the real dataset, it clearly outperformed the other methods, in terms of the fraction of correct classifications, mean error (ME), and root mean square error (RMSE). The proposed approach may be beneficial to standardize the selection of the number of muscle synergies between different research laboratories, independent of arbitrary thresholds

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How to improve robustness in muscle synergy extraction

Authors:
M. Ghislieri, V. Agostini, and M. Knaflitz
Journal:
2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
DOI:
10.1109/EMBC.2019.8856438
Year:
2019
Abstract:

The muscle synergy theory was widely used in literature to assess the modular organization of the central nervous system (CNS) during human locomotion. The extraction of muscle synergies may be strongly influenced by the preprocessing techniques applied to surface electromyographic (sEMG) signals. The aim of this contribution is to assess the robustness improvement in muscle synergy extraction obtained using an innovative pre-processing technique with respect to the standard procedure. The new pre-processing technique that we propose is based on the extraction of principal muscle activation intervals (necessary to accomplish a specific biomechanical task during gait) from the original sEMG signals, discarding the secondary muscle activation intervals (activations that occur only in some strides with auxiliary functions). Results suggest that the extraction of the principal activation intervals from sEMG provide a more consistent and stable description of the modular organization of the CNS with respect to the standard pre-processing procedure.

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Muscle synergies extracted using principal activations: improvement of robustness and interpretability

Authors:
M. Ghislieri, V. Agostini, and M. Knaflitz
Journal:
IEEE Transactions on Neural Systems and Rehabilitation Engineering
DOI:
10.1109/TNSRE.2020.2965179
Year:
2020
Abstract:

The muscle synergy theory has been widely used to assess the modular organization of the central nervous system (CNS) during human locomotion. The pre-processing approach applied to the surface electromyographic (sEMG) signals influences the extraction of muscle synergies. The aim of this contribution is to assess the improvements in muscle synergy extraction obtained by using an innovative pre-processing approach. We evaluate the improvement in terms of the possible variation in the number of muscle synergies, of the intra-subject consistency, of the robustness, and of the interpretability of the results. The pre-processing approach presented in this paper is based on the extraction of the muscle principal activations (muscle activations strictly necessary to accomplish a specific biomechanical task) from the original sEMG signals, to then obtain muscle synergies using principal activations only. The results herein presented show that the application of this novel approach for the extraction of the muscle synergies provides a more robust and easily interpretable description of the modular organization of the CNS with respect to the standard pre-processing approach.

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Muscle Synergy Assessment During Single-Leg Stance

Authors:
M. Ghislieri, M. Knaflitz, L. Labanca, G. Barone, L. Bragonzoni, M. G. Benedetti, and V. Agostini
Journal:
IEEE Transactions on Neural Systems and Rehabilitation Engineering
DOI:
10.1109/TNSRE.2020.3030847
Year:
2020
Abstract:

In the study of muscle synergies during the maintenance of single-leg stance there are several methodological issues that must be taken into account before muscle synergy extraction. In particular, it is important to distinguish between epochs of surface electromyography (sEMG) signals corresponding to “well-balanced” and “unbalanced” single-leg stance, since different motor control strategies could be used to maintain balance. The aim of this work is to present and define a robust procedure to distinguish between “well-balanced” and “unbalanced” single-leg stance to be chosen as input for the algorithm used to extract muscle synergies. Our results demonstrate that the proposed approach for the selection of sEMG epochs relative to “well-balanced” and “unbalanced” single-leg stance is robust with respect to the selection of the segmentation threshold, revealing a high consistency in the number of muscle synergies and high similarity among the weight vectors (correlation values range from 0.75 to 0.97). Moreover, differences in terms of average recruitment levels and balance control strategies were detected, suggesting a slightly different modular organization between “well-balanced” and “unbalanced” single-leg stance. In conclusion, this approach can be successfully used as a pre-processing step before muscle synergy extraction, allowing for a better assessment of motor control strategies during the single-leg stance task.

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Postural control after traumatic brain injury in patients with neuro-ophthalmic deficits

Authors:
V. Agostini, E. Chiaramello, C. Bredariol, C. Cavallini and M. Knaflitz
Journal:
Gait & Posture
DOI:
10.1016/j.gaitpost.2011.05.008
Year:
2011
Abstract:

Postural instability is a common and devastating consequence of traumatic brain injury (TBI). The majority of TBI patients also suffer from neuro-ophthalmic deficits that can be an important contributing element to their sensation of vertigo and dizziness. Static posturography aims at the objective evaluation of patient balance impairment, but is usually affected by large inter- and intra-subject variability. Here we propose a protocol based on 10 randomized trials stimulating in different ways the visual and vestibular systems. Due to its completeness, our protocol highlights the specific residual difficulties of each patient in the various conditions. In this way, it was possible to evidence significant balance abnormalities in TBI patients with respect to controls. Moreover, by means of a multivariate analysis we were able to discriminate different levels of residual neuro-ophthalmic impairment.

Read more

Postural sway in volleyball players

Authors:
V. Agostini, E. Chiaramello, L. Canavese, C. Bredariol and M. Knaflitz
Journal:
Human Movement Science
DOI:
10.1016/j.humov.2013.01.002
Year:
2013
Abstract:

The aim of this work was to analyze the postural sway of volleyball players in bipedal quiet stance. The center of pressure (CoP) was measured in 46 athletes and 42 non-athlete controls. Each subject was tested in 10 different conditions, 5 with their eyes open and 5 with their eyes closed. Volleyball players showed greater CoP ellipses, suggesting a different model of sensory integration in their postural stability. A multivariate approach to data analysis demonstrated that the postural sway of the two groups was different when the subjects kept their eyes open, but it was not with visual deprivation. This could partially be explained by the better ‘dynamic’ visual acuity of athletes, since possible (‘static’) refractive errors were corrected for both groups. Furthermore, we expected that national players, engaged in more intensive training programs, were more different from controls than regional ones, and that defensive players, whose role requires the quickest reaction times, were more different from controls than hitters. Our results confirmed these hypothesis. The protocol presented might be useful to assess the efficacy of intensive sport training programs and/or to select elite players with an aptitude for a specific playing position.

Read more

The Effect of Signal-to-Noise Ratio on Muscle Synergy Extraction

Authors:
M. Ghislieri, V. Agostini, and M. Knaflitz
Journal:
2018 IEEE Life Sciences Conference (LSC)
DOI:
10.1109/LSC.2018.8572075
Year:
2018
Abstract:

The modular organization of the central nervous system (CNS) during motor tasks was widely assessed by means of muscle synergies. The aim of this work was to assess the impact of the Signal-to-Noise Ratio (SNR) on muscle synergies extracted from synthetic surface electromyographic (sEMG) signals that simulate the muscle activity of the lower limb during walking. To evaluate the effect of the SNR, the similarity between the weights vectors and the activation coefficients extracted from real sEMG signals and from simulated sEMG signals at different values of SNR was computed. Results reveal that muscle synergy extraction is strongly dependent upon the quality of the sEMG signals simulated.

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The role of central vision in posture: Postural sway adaptations in Stargardt patients

Authors:
V. Agostini, A. Sbrollini, C. Cavallini, A. Busso, G. Pignata and M. Knaflitz
Journal:
Gait & Posture
DOI:
10.1016/j.gaitpost.2015.10.003
Year:
2016
Abstract:

The role of central and peripheral vision in the maintenance of upright stance is debated in literature. Stargardt disease causes visual deficits affecting the central field, but leaving unaltered a patient’s peripheral vision. Hence, the study of this rare pathology gives the opportunity to selectively investigate the role of central vision in posture. Postural sway in quiet stance was analyzed in 10 Stargardt patients and 10 control subjects, in three different conditions: (1) eyes closed, (2) eyes open, gazing at a fixed target, and (3) eyes open, tracking a moving target. Stargardt patients outperformed controls in the condition with eyes closed, showing a reduced root mean square (RMS) of the medio-lateral COP displacement, while their performance was not significantly different from controls in the antero-posterior direction. There were no significant differences between patients and controls in open eyes conditions. These results suggest that Stargardt patients adapted to a different visual-somatosensory integration, relying less on vision, especially in the medio-lateral direction. Hence, the central vision seems to affect mostly the medio-lateral direction of postural sway. This finding supports the plausibility of the “functional sensitivity hypothesis”, that assigns complementary roles to central and peripheral vision in the control of posture.

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Telemedicine

A wearable device to assess postural sway

Authors:
V. Agostini, E. Aiello, D. Fortunato, M. Knaflitz, and L. Gastaldi
Journal:
2019 IEEE 23rd International Symposium on Consumer Technologies (ISCT)
DOI:
10.1109/ISCE.2019.8901019
Year:
2019
Abstract:

The maintenance of balance in upright stance is traditionally evaluated using heavy and expensive force platforms. The aim of this work is to prove the usefulness of a low-cost wearable sensor (an actigraph) to assess postural sway. We compared the performance of the device to a gold standard force platform. We analyzed measurements of postural sway in four conditions differently challenging the subject: with eyes open or closed, while keeping a small or large base of support. We estimated the main postural parameters (ellipse area, mediolateral and antero-posterior root-mean square, eccentricity, sway path length) considering: 1) acceleration data recorded by the actigraph, and 2) traditional COP data obtained from the force platform. We found that it is possible to clearly distinguish the differences among the postural parameters, obtained in the various balance conditions, also using acceleration data. Our results show that the wearable device allows for obtaining information similar to those achievable by the force platform. This support the use of wearable devices to assess postural balance, in a handy and cheap manner.

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