Browsing by Author "Rennaker, Robert L., II"
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Item A Novel Approach to Automate Measurement and Training of Hand and Wrist Motor Functions(2018-08) Grasse, Katelyn Millay; 0000-0002-7953-1466 (Grasse, KM); Rennaker, Robert L., IIMillions of people around the world suffer chronic upper extremity disability. Reliable measurement of arm function is critical for development of therapies to improve recovery after impairment. In this study, we report a suite of automated rehabilitative tools to allow simple, quantitative assessment of hand and wrist motor functions. We measured range of motion and force production using these devices in cSCI participants with a range of upper limb disability and in neurologically intact participants at two time points separated by approximately four months. Additionally, we determined whether measures collected with the rehabilitative tools correlated with standard upper limb assessments, including the Graded Redefined Assessment of Strength, Sensibility, and Prehension (GRASSP) and the Jebsen Hand Function Test (JHFT). We find that the rehabilitative devices provide sensitive, accurate assessment of upper limb function in physical units over time in SCI participants and are well-correlated with standard assessments. These results indicate that these tools represent a reliable system for longitudinal evaluation of upper extremity function after cSCI and may provide a framework to assess the efficacy of strategies aimed at improving recovery of upper limb function. Finally, we demonstrate the feasibility of using the system with video games to deliver automated repetitive motor therapy.Item Studies in RF Power Communication, SAR, and Temperature Elevation in Wireless Implantable Neural InterfacesZhao, Y.; Tang, L.; Rennaker, Robert L., II; Hutchens, C.; Ibrahim, T. S.; 0000 0001 2879 2132 (Rennaker, RL)Implantable neural interfaces are designed to provide a high spatial and temporal precision control signal implementing high degree of freedom real-time prosthetic systems. The development of a Radio Frequency (RF) wireless neural interface has the potential to expand the number of applications as well as extend the robustness and longevity compared to wired neural interfaces. However, it is well known that RF signal is absorbed by the body and can result in tissue heating. In this work, numerical studies with analytical validations are performed to provide an assessment of power, heating and specific absorption rate (SAR) associated with the wireless RF transmitting within the human head. The receiving antenna on the neural interface is designed with different geometries and modeled at a range of implanted depths within the brain in order to estimate the maximum receiving power without violating SAR and tissue temperature elevation safety regulations. Based on the size of the designed antenna, sets of frequencies between 1 GHz to 4 GHz have been investigated. As expected the simulations demonstrate that longer receiving antennas (dipole) and lower working frequencies result in greater power availability prior to violating SAR regulations. For a 15 mm dipole antenna operating at 1.24 GHz on the surface of the brain, 730 uW of power could be harvested at the Federal Communications Commission (FCC) SAR violation limit. At approximately 5 cm inside the head, this same antenna would receive 190 uW of power prior to violating SAR regulations. Finally, the 3-D bio-heat simulation results show that for all evaluated antennas and frequency combinations we reach FCC SAR limits well before 1 °C. It is clear that powering neural interfaces via RF is possible, but ultra-low power circuit designs combined with advanced simulation will be required to develop a functional antenna that meets all system requirements.Item Wireless Devices for Peripheral Nerve Stimulation and Recording(2018-12) Sivaji, Vishnoukumaar; Rennaker, Robert L., II; Grasse, Dane W.Treatment of neurological disorders by neuromodulation has expanded the market for peripheral nerve stimulators and recording devices. While wireless powering can extend the life of these devices, the development risks associated with custom solutions have emerged as a barrier. We describe circuit designs for miniaturized stimulation and recording devices built only using commercial off-the-shelf components. We have used these circuit designs to build a human grade wireless nerve stimulation system that is not only small but also has no battery or leads, greatly reducing the risks associated with other devices available in the market. The implanted device can be programmed wirelessly to deliver charge balanced biphasic current pulses of varying amplitudes, pulse widths, frequencies and train durations. We have tested the device on the bench and in acute in vivo settings to demonstrate the reliability and efficacy of the stimulation. We have also conducted a chronic safety study in dogs to show that the device is safe to be implanted in humans. The results establish the potential of this device to advance the emerging field of closed loop neuromodulation systems.