96 research outputs found

    Mutual interferences and design principles for mechatronic devices in magnetic resonance imaging

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    Purpose: Robotic and mechatronic devices that work compatibly with magnetic resonance imaging (MRI) are applied in diagnostic MRI, image-guided surgery, neurorehabilitation and neuroscience. MRI-compatible mechatronic systems must address the challenges imposed by the scanner's electromagnetic fields. We have developed objective quantitative evaluation criteria for device characteristics needed to formulate design guidelines that ensure MRI-compatibility based on safety, device functionality and image quality. Methods: The mutual interferences between an MRI system and mechatronic devices working in its vicinity are modeled and tested. For each interference, the involved components are listed, and a numerical measure for "MRI-compatibility” is proposed. These interferences are categorized into an MRI-compatibility matrix, with each element representing possible interactions between one part of the mechatronic system and one component of the electromagnetic fields. Based on this formulation, design principles for MRI-compatible mechatronic systems are proposed. Furthermore, test methods are developed to examine whether a mechatronic device indeed works without interferences within an MRI system. Finally, the proposed MRI-compatibility criteria and design guidelines have been applied to an actual design process that has been validated by the test procedures. Results: Objective and quantitative MRI-compatibility measures for mechatronic and robotic devices have been established. Applying the proposed design principles, potential problems in safety, device functionality and image quality can be considered in the design phase to ensure that the mechatronic system will fulfill the MRI-compatibility criteria. Conclusion: New guidelines and test procedures for MRI instrument compatibility provide a rational basis for design and evaluation of mechatronic devices in various MRI applications. Designers can apply these criteria and use the tests, so that MRI-compatibility results can accrue to build an experiential databas

    fMRI assessment of upper extremity related brain activation with an MRI-compatible manipulandum

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    Purpose: Longitudinal studies to evaluate the effect of rehabilitative therapies require an objective, reproducible and quantitative means for testing function in vivo. An fMRI assessment tool for upper extremity related brain activation using an MRI-compatible manipulandum was developed and tested for use in neurorehabilitation research. Methods: Fifteen healthy, right-handed subjects participated in two fMRI sessions, which were three to four weeks apart. A block design paradigm, composed of three conditions of subject-passive movement, subject-active movement and rest, was employed for the fMRI recordings. During the rest condition, subjects simply held the device handle without applying any force or movement. The same type of auditory and visual instructions were given in all the three conditions, guiding the subjects to perform the motor tasks interactively with the MRI-compatible arm manipulandum. The tasks were controlled across the fMRI sessions. The subjects' brain activation was recorded by fMRI, and their behavioral performance was recorded by the manipulandum. The brain network activated by the subjects' interaction with the manipulandum was identified, and the reproducibility and reliability of the obtained activation were determined. Results: All subjects completed the trial protocol. Two subjects were excluded from analysis due to head motion artifacts. All passive movements were performed well. Four out of the total 780 active movements were missed by two subjects. Brain activation was found in the contralateral sensorimotor cortex, secondary somatosensory cortex and non-primary motor cortex as well as in subcortical areas in the thalamus, basal ganglia and the cerebellum. These activations were consistent across the two fMRI sessions. Conclusion: The MRI-compatible manipulandum elicited robust and reproducible brain activations in healthy subjects during the subject-active and subject-passive upper extremity motor tasks with a block design paradigm. This system is promising for many applications in neurorehabilitation research and may be useful for longitudinal studie

    Zinc-Chelating Mechanism of Sea Cucumber (Stichopus japonicus)-Derived Synthetic Peptides

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    In this study, three synthetic zinc-chelating peptides (ZCPs) derived from sea cucumber hydrolysates with limited or none of the common metal-chelating amino-acid residues were analyzed by flame atomic absorption spectroscopy, circular dichroism spectroscopy, size exclusion chromatography, zeta-potential, Fourier transform infrared spectroscopy, Raman spectroscopy and nuclear magnetic resonance spectroscopy. The amount of zinc bound to the ZCPs reached maximum values with ZCP:zinc at 1:1, and it was not further increased by additional zinc presence. The secondary structures of ZCPs were slightly altered, whereas no formation of multimers was observed. Furthermore, zinc increased the zeta-potential value by neutralizing the negatively charged residues. Only free carboxyl in C-terminus of ZCPs was identified as the primary binding site of zinc. These results provide the theoretical foundation to understand the mechanism of zinc chelation by peptides

    A novel plantar pressure analysis method to signify gait dynamics in Parkinson's disease

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    Plantar pressure can signify the gait performance of patients with Parkinson's disease (PD). This study proposed a plantar pressure analysis method with the dynamics feature of the sub-regions plantar pressure signals. Specifically, each side's plantar pressure signals were divided into five sub-regions. Moreover, a dynamics feature extractor (DFE) was designed to extract features of the sub-regions signals. The radial basis function neural network (RBFNN) was used to learn and store gait dynamics. And a classification mechanism based on the output error in RBFNN was proposed. The classification accuracy of the proposed method achieved 100.00% in PD diagnosis and 95.89% in severity assessment on the online dataset, and 96.00% in severity assessment on our dataset. The experimental results suggested that the proposed method had the capability to signify the gait dynamics of PD patients

    A Reliability Study on Brain Activation During Active and Passive Arm Movements Supported by an MRI-Compatible Robot

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    In neurorehabilitation, longitudinal assessment of arm movement related brain function in patients with motor disability is challenging due to variability in task performance. MRI-compatible robots monitor and control task performance, yielding more reliable evaluation of brain function over time. The main goals of the present study were first to define the brain network activated while performing active and passive elbow movements with an MRI-compatible arm robot (MaRIA) in healthy subjects, and second to test the reproducibility of this activation over time. For the fMRI analysis two models were compared. In model 1 movement onset and duration were included, whereas in model 2 force and range of motion were added to the analysis. Reliability of brain activation was tested with several statistical approaches applied on individual and group activation maps and on summary statistics. The activated network included mainly the primary motor cortex, primary and secondary somatosensory cortex, superior and inferior parietal cortex, medial and lateral premotor regions, and subcortical structures. Reliability analyses revealed robust activation for active movements with both fMRI models and all the statistical methods used. Imposed passive movements also elicited mainly robust brain activation for individual and group activation maps, and reliability was improved by including additional force and range of motion using model 2. These findings demonstrate that the use of robotic devices, such as MaRIA, can be useful to reliably assess arm movement related brain activation in longitudinal studies and may contribute in studies evaluating therapies and brain plasticity following injury in the nervous system
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