Principal components analysis based control of a multi-dof underactuated prosthetic hand

<p>Abstract</p> <p>Background</p> <p>Functionality, controllability and cosmetics are the key issues to be addressed in order to accomplish a successful functional substitution of the human hand by means of a prosthesis. Not only the prosthesis should duplicate the human hand in shape, functionality, sensorization, perception and sense of body-belonging, but it should also be controlled as the natural one, in the most intuitive and undemanding way. At present, prosthetic hands are controlled by means of non-invasive interfaces based on electromyography (EMG). Driving a multi degrees of freedom (DoF) hand for achieving hand dexterity implies to selectively modulate many different EMG signals in order to make each joint move independently, and this could require significant cognitive effort to the user.</p> <p>Methods</p> <p>A Principal Components Analysis (PCA) based algorithm is used to drive a 16 DoFs underactuated prosthetic hand prototype (called CyberHand) with a two dimensional control input, in order to perform the three prehensile forms mostly used in Activities of Daily Living (ADLs). Such Principal Components set has been derived directly from the artificial hand by collecting its sensory data while performing 50 different grasps, and subsequently used for control.</p> <p>Results</p> <p>Trials have shown that two independent input signals can be successfully used to control the posture of a real robotic hand and that correct grasps (in terms of involved fingers, stability and posture) may be achieved.</p> <p>Conclusions</p> <p>This work demonstrates the effectiveness of a bio-inspired system successfully conjugating the advantages of an underactuated, anthropomorphic hand with a PCA-based control strategy, and opens up promising possibilities for the development of an intuitively controllable hand prosthesis.</p

Real-time myoelectric control of a multi-fingered hand prosthesis using principal components analysis

<p>Abstract</p> <p>Background</p> <p>In spite of the advances made in the design of dexterous anthropomorphic hand prostheses, these sophisticated devices still lack adequate control interfaces which could allow amputees to operate them in an intuitive and close-to-natural way. In this study, an anthropomorphic five-fingered robotic hand, actuated by six motors, was used as a prosthetic hand emulator to assess the feasibility of a control approach based on Principal Components Analysis (PCA), specifically conceived to address this problem. Since it was demonstrated elsewhere that the first two principal components (PCs) can describe the whole hand configuration space sufficiently well, the controller here employed reverted the PCA algorithm and allowed to drive a multi-DoF hand by combining a two-differential channels EMG input with these two PCs. Hence, the novelty of this approach stood in the PCA application for solving the challenging problem of best mapping the EMG inputs into the degrees of freedom (DoFs) of the prosthesis.</p> <p>Methods</p> <p>A clinically viable two DoFs myoelectric controller, exploiting two differential channels, was developed and twelve able-bodied participants, divided in two groups, volunteered to control the hand in simple grasp trials, using forearm myoelectric signals. Task completion rates and times were measured. The first objective (assessed through one group of subjects) was to understand the effectiveness of the approach; i.e., whether it is possible to drive the hand in real-time, with reasonable performance, in different grasps, also taking advantage of the direct visual feedback of the moving hand. The second objective (assessed through a different group) was to investigate the intuitiveness, and therefore to assess statistical differences in the performance throughout three consecutive days.</p> <p>Results</p> <p>Subjects performed several grasp, transport and release trials with differently shaped objects, by operating the hand with the myoelectric PCA-based controller. Experimental trials showed that the simultaneous use of the two differential channels paradigm was successful.</p> <p>Conclusions</p> <p>This work demonstrates that the proposed two-DoFs myoelectric controller based on PCA allows to drive in real-time a prosthetic hand emulator into different prehensile patterns with excellent performance. These results open up promising possibilities for the development of intuitive, effective myoelectric hand controllers.</p

EPHA2 is a predictive biomarker of resistance and a potential therapeutic target for improving anti-epidermal growth factor receptor therapy in colorectal cancer

The EPHA2 tyrosine kinase receptor is implicated in tumor progression and targeted therapies resistance. We evaluated EPHA2 as potential resistance marker to the anti-epidermal growth factor receptor (EGFR) monoclonal antibody cetuximab in colorectal cancer (CRC). We studied activation of EPHA2 in a panel of human CRC cell lines sensitive or resistant to anti-EGFR drugs. The in vitro and in vivo effects of ALW-II-41-27 (a EPHA2 inhibitor) and/or cetuximab treatment were tested. Formalin-fixed paraffin-embedded tumor specimens from 82 RAS wild type (WT) metastatic CRC patients treated with FOLFIRI +cetuximab as first line therapy in the CAPRI-GOIM trial were assessed for EPHA2 expression by immunohistochemistry and correlated with treatment efficacy. EPHA2 was differentially activated in CRC cell lines. Combined treatment with ALW-II-41-27 plus cetuximab reverted primary and acquired resistance to cetuximab causing cell growth inhibition, inducing apoptosis and cell cycle G1-G2 arrest. In tumor xenografts models, upon progression to cetuximab, ALW II-41-27 addition significantly inhibited tumor growth. EPHA2 protein expression was detected in 55/82 tumor samples, frequently expressed in less differentiated and left-sided tumors. High levels of EPHA2 significantly correlated with worse progression free survival [8.6 months (CI 95%: 6.4-10.8) vs 12.3 months (CI 95%: 10.4-14.2) (P=0.03)] and with increased progression rate (29% vs 9%, P=0.02). A specific EPHA2 inhibitor reverts in vitro and in vivo primary and acquired resistance to anti-EGFR therapy. EPHA2 levels are significantly associated with worse outcome in patients treated with FOLFIRI+cetuximab. These results highlight EPHA2 as a potential therapeutic target in metastatic CRC

Atazanavir and lopinavir profile in pregnant women with HIV: Tolerability, activity and pregnancy outcomes in an observational national study

Background: Atazanavir and lopinavir represent the main HIV protease inhibitors recommended in pregnancy, but comparative data in pregnant women are limited. Methods: Women from a national observational study, exposed in pregnancy to either atazanavir or lopinavir, were compared for glucose and lipid profiles, liver function tests, CD4 count, HIV RNA and main pregnancy outcomes. Statistical methods included univariate and multivariable analyses. Results: The study population included 428 pregnancies (lopinavir, 322; atazanavir, 106). The lopinavir group was characterized by higher rates of HIV diagnosis in pregnancy and treatment indication for maternal health, lower CD4 counts, higher HIV RNA levels, less frequent antiretroviral treatment at conception and shorter duration of drug exposure during pregnancy. No differences in pregnancy outcomes, glucose metabolism and weight gain were observed. The two groups also showed in a multivariable analysis similar odds for detectable HIV RNA in the third trimester (adjusted OR 0.85, 95% CI 0.35-2.10, P1/40.730). Total lipid levels were significantly higher in the lopinavir group (median values in the third trimester 239 versus 221 mg/dL for total cholesterol and 226 versus 181 mg/dL for triglycerides; P<0.001 for both comparisons) and bilirubin levels were significantly higher in the atazanavir group (1.53 versus 0.46 mg/dL, P<0.001). Conclusions: In this observational study atazanavir and lopinavir showed similar safety and activity in pregnancy, with no differences in the main pregnancy outcomes. Atazanavir usewas associated with a better lipid profile and with higher bilirubin levels. Overall, the study findings confirm that these two HIV protease inhibitors represent equally valid alternative options. \ua9 The Author 2013.Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved

HBV coinfection is associated with reduced CD4 response to antiretroviral treatment in pregnancy

Objective: To evaluate the impact of Hepatitis B virus (HBV) coinfection on response to antiretroviral treatment in pregnant women with HIV. Methods: Retrospective analysis of a large case series of pregnant women with HIV in Italy; outcome measures were CD4 changes, HIV viral load, and main pregnancy outcomes (preterm delivery, low birthweight, intrauterine growth restriction, mode of delivery, and major birth defects). Results: Rate of HBV coinfection among 1462 pregnancies was 12.0%. Compared to the HBV-uninfected, HBV-coinfected women had a significantly lower median CD4 cell gain between first and third trimester (26.5 vs. 60 cells/mm3, p = 0.034), with similar rate of undetectable (<50 copies/ml) HIV-RNA at third trimester (70.5% vs. 65.2%, p = 0.229), and no differences in all the main maternal and infant outcomes. A multivariable linear regression analysis identified four variables significantly and independently associated with a lower CD4 response in pregnancy: HBV coinfection (â\u80\u9335 cells/mm3), being on antiretroviral treatment at conception (â\u80\u9359.7 cells/mm3), AIDS status (â\u80\u9359.8 cells/mm3) and higher first CD4 levels in pregnancy (â\u80\u930.24 cells per unitary CD4 increase). Conclusions: HBV coinfection had no adverse influence on the main pregnancy outcomes or on HIV viral load suppression in late pregnancy but was associated with a significantly reduced CD4 response in pregnancy. This effect might have clinical relevance, particularly in women with advanced immune deterioration