fMRI-compatible rehabilitation hand device

BACKGROUND: Functional magnetic resonance imaging (fMRI) has been widely used in studying human brain functions and neurorehabilitation. In order to develop complex and well-controlled fMRI paradigms, interfaces that can precisely control and measure output force and kinematics of the movements in human subjects are needed. Optimized state-of-the-art fMRI methods, combined with magnetic resonance (MR) compatible robotic devices for rehabilitation, can assist therapists to quantify, monitor, and improve physical rehabilitation. To achieve this goal, robotic or mechatronic devices with actuators and sensors need to be introduced into an MR environment. The common standard mechanical parts can not be used in MR environment and MR compatibility has been a tough hurdle for device developers. METHODS: This paper presents the design, fabrication and preliminary testing of a novel, one degree of freedom, MR compatible, computer controlled, variable resistance hand device that may be used in brain MR imaging during hand grip rehabilitation. We named the device MR_CHIROD (Magnetic Resonance Compatible Smart Hand Interfaced Rehabilitation Device). A novel feature of the device is the use of Electro-Rheological Fluids (ERFs) to achieve tunable and controllable resistive force generation. ERFs are fluids that experience dramatic changes in rheological properties, such as viscosity or yield stress, in the presence of an electric field. The device consists of four major subsystems: a) an ERF based resistive element; b) a gearbox; c) two handles and d) two sensors, one optical encoder and one force sensor, to measure the patient induced motion and force. The smart hand device is designed to resist up to 50% of the maximum level of gripping force of a human hand and be controlled in real time. RESULTS: Laboratory tests of the device indicate that it was able to meet its design objective to resist up to approximately 50% of the maximum handgrip force. The detailed compatibility tests demonstrated that there is neither an effect from the MR environment on the ERF properties and performance of the sensors, nor significant degradation on MR images by the introduction of the MR_CHIROD in the MR scanner. CONCLUSION: The MR compatible hand device was built to aid in the study of brain function during generation of controllable and tunable force during handgrip exercising. The device was shown to be MR compatible. To the best of our knowledge, this is the first system that utilizes ERF in MR environment

Diffusion tensor and volumetric magnetic resonance imaging using an MR-compatible hand-induced robotic device suggests training-induced neuroplasticity in patients with chronic stroke

Stroke is the third leading cause of mortality and a frequent cause of long-term adult impairment. Improved strategies to enhance motor function in individuals with chronic disability from stroke are thus required. Post-stroke therapy may improve rehabilitation and reduce long-term disability; however, objective methods for evaluating the specific impact of rehabilitation are rare. Brain imaging studies on patients with chronic stroke have shown evidence for reorganization of areas showing functional plasticity after a stroke. In this study, we hypothesized that brain mapping using a novel magnetic resonance (MR)-compatible hand device in conjunction with state-of-the-art magnetic resonance imaging (MRI) can serve as a novel biomarker for brain plasticity induced by rehabilitative motor training in patients with chronic stroke. This hypothesis is based on the premises that robotic devices, by stimulating brain plasticity, can assist in restoring movement compromised by stroke-induced pathological changes in the brain and that these changes can then be monitored by advanced MRI. We serially examined 15 healthy controls and 4 patients with chronic stroke. We employed a combination of diffusion tensor imaging (DTI) and volumetric MRI using a 3-tesla (3T) MRI system using a 12-channel Siemens Tim coil and a novel MR-compatible hand-induced robotic device. DTI data revealed that the number of fibers and the average tract length significantly increased after 8 weeks of hand training by 110% and 64%, respectively (p<0.001). New corticospinal tract (CST) fibers projecting progressively closer to the motor cortex appeared during training. Volumetric data analysis showed a statistically significant increase in the cortical thickness of the ventral postcentral gyrus areas of patients after training relative to pre-training cortical thickness (p<0.001). We suggest that rehabilitation is possible for a longer period of time after stroke than previously thought, showing that structural plasticity is possible even after 6 months due to retained neuroplasticity. Our study is an example of personalized medicine using advanced neuroimaging methods in conjunction with robotics in the molecular medicine era

Functional MRI of Rehabilitation in Chronic Stroke Patients Using Novel MR-Compatible Hand Robots

We monitored brain activation after chronic stroke by combining functional magnetic resonance imaging (fMRI) with a novel MR-compatible, hand-induced, robotic device (MR_CHIROD). We evaluated 60 fMRI datasets on a 3 T MR system from five right-handed patients with left-sided stroke ≥6 months prior and mild to moderate hemiparesis. Patients trained the paretic right hand at approximately 75% of maximum strength with an exercise ball for 1 hour/day, 3 days/week for 4 weeks. Multi-level fMRI data were acquired before, during training, upon completion of training, and after a non-training period using parallel imaging employing GeneRalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) while the participant used the MR_CHIROD. Training increased the number of activated sensorimotor cortical voxels, indicating functional cortical plasticity in chronic stroke patients. The effect persisted four weeks after training completion, indicating the potential of rehabilitation in inducing cortical plasticity in chronic stroke patients

Functional MRI of Rehabilitation in Chronic Stroke Patients Using Novel MR-Compatible Hand Robots

We monitored brain activation after chronic stroke by combining functional magnetic resonance imaging (fMRI) with a novel MR-compatible, hand-induced, robotic device (MR_CHIROD). We evaluated 60 fMRI datasets on a 3 T MR system from five right-handed patients with left-sided stroke ≥6 months prior and mild to moderate hemiparesis. Patients trained the paretic right hand at approximately 75% of maximum strength with an exercise ball for 1 hour/day, 3 days/week for 4 weeks. Multi-level fMRI data were acquired before, during training, upon completion of training, and after a non-training period using parallel imaging employing GeneRalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) while the participant used the MR_CHIROD. Training increased the number of activated sensorimotor cortical voxels, indicating functional cortical plasticity in chronic stroke patients. The effect persisted four weeks after training completion, indicating the potential of rehabilitation in inducing cortical plasticity in chronic stroke patients

Cardiovascular molecular imaging

Although there have been significant improvements in the treatment of cardiovascular diseases they still remain the main cause of morbidity and mortality globally. Currently available diagnostic approaches may not be adequate to detect pathologic changes during the early disease stages, which may be valuable for risk stratification and also to assess a response to a therapy. Therefore molecular imaging techniques such as Contrast Enhanced Ultrasound (CEU) molecular imaging to noninvasively image pathophysiologic processes on a molecular level have been developed. For CEU molecular imaging targeted microbubbles are used as contrast agent. However it has been shown that the targeting efficiency of microbubbles is low with retention of less than 5% of targeted microbubbles under high flow shear rate. Furthermore the application of CEU molecular imaging in assessing a response to therapeutic agents aiming at preventing cardiovascular events has not yet been studied. Therefore, in this PhD thesis first we investigated the influence of microbubble shell characteristics on targeting efficiency of microbubbles. Second we used ultrasound molecular imaging to assess the anti-inflammatory effects of statins in vascular inflammation in relevant murine models of atherosclerosis and finally we investigated the short-term effects of treatment with apocynin on endothelial inflammation and thrombogenicity in a murine model of early atherosclerosis by application of ultrasound molecular imaging. In the first part of our study we demonstrated that microbubbles with a longer PEG spacer arm, which is used for the conjugation of the targeting ligand on the microbubble surface, yield a better targeting efficiency compared to the microbubbles with a shorter PEG spacer arm. The improvement of the targeting efficiency of microbubbles with the longer PEG spacer arm could be due to better accessibility of the conjugated ligands on the microbubble surface to their endothelial target and also due to more stable bonds formed between ligands presented by longer PEG spacer arms to their target under flow conditions. In addition the targeting efficiency of microbubbles was influenced by the degree to which the endothelial target was projected away from the endothelial surface. The attachment efficiency was low for short molecular targets, which were hidden in the glycocaylyx. This observation could have implications for the selection of potential molecular imaging targets. Moreover as the interaction of targeted microbubbles with their endothelial target occurs in the presence of the endothelial glycocalyx the thickness of the glycocalyx in the vessels may have an important influence on microbubble attachment efficiency. In the second project we could show that CEU molecular imaging can assess the impact of therapy on endothelial inflammation in a murine model of early atherosclerosis where high frequency ultrasound imaging of the aortic wall was unable to show the effects of treatment on the atherosclerotic plaques. In atherosclerosis endothelial expression of the inflammatory cell adhesion molecule Vascular Cell Adhesion Molecule- 1 (VCAM-1) plays an important role in the initiation and progression of atherosclerosis. CEU molecular imaging by targeting microbubbles to VCAM-1 demonstrated a selective signal enhancement for these microbubbles compared to control microbubbles in non- treated animals but not in atorvastatin treated animals. Therefore given that phenotypic changes on the endothelial surface are responsible for the initiation of atherosclerosis, this method could be used for assessing treatment effects during the initial stages of atherosclerosis. Lastly, We were able to demonstrate that short-term treatment with apocynin, an antioxidant, anti-inflammatory agent, in a mouse model of early atherosclerosis results in reduced aortic endothelial inflammation presented as a reduced expression of endothelial VCAM-1 and platelet adhesion. However, these anti-inflammatory effects were not associated with measurable reductions in vascular NADPH oxidase activity or superoxide content. Our findings from CEU molecular imaging demonstrated that there is a lower attachment of microbubbles targeted to endothelial VCAM-1 and also activated platelets to aortic endothelial cells after treatment with apocynin compared to the group which were imaged at baseline and a group which received saline treatment as a control group. However, apocynin therapy did not reduce ROS content or superoxide generation. These effects of apocynin are probably due to ROS- independent mechanisms in the early stages of atherosclerotic plaque development. In conclusion CEU molecular imaging could be useful in the future for assessing the effects of drug treatment in individual patients, but also for screening of the effects of novel drug classes in preclinical field

Journal of Heat Transfer Film Effectiveness Downstream of a Row of Compound Angle Film Holes

Effects that two different compound-angle film-hole configuration

Silicone made contractile dielectric elastomer actuators inside 3-Tesla MRI environment

New actuators are greatly demanded today in order to develop magnetic resonance imaging (MRI)-compatible mechatronic systems capable of extended and improved capabilities. They are particularly needed for MRI-guided interventional or rehabilitation procedures. Actuators based on dielectric elastomers, a specific class of electroactive polymers, appear as suitable candidates for new MRI-compatible technologies, due to their intrinsic material properties and working principle. This paper presents the first investigation on the MRI compatibility of a recently developed linear contractile actuator made of a silicone elastomer. The assessed absence of any degradation of both the actuator electromechanical performance in the MRI environment and the quality of images acquired from a phantom demonstrated the MRI compatibility of the actuator. These results suggest the suitability of this soft actuation technology as a possible new entry in the class of MRI compatible mechatronic systems. ©2008 IEEE

MRI Compatibility of Silicone Made Contractile Dieletric Elastomer Actuators

Actuators based on dielectric elastomers, a specific class of electroactive polymers, appear to be suitable candidates for new MRI-compatible technologies, due to their intrinsic material properties and working principle. This paper presents the first investigation into the MRI compatibility of a recently developed linear contractile actuator made of a silicone elastomer. The apparent absence of any degradation of both the actuator electromechanical performance in the MRI environment and the quality of images acquired from a phantom demonstrates the MRI compatibility of the actuator. These results suggest the suitability of this soft actuation technology as a possible new entry in the class of MRI-compatible mechatronic system