Impedance and Noise Characterizations of Utah and Microwire Electrode Arrays
Read Description
A total of 80 electrodes were implanted across five rats and measured under deep anesthesia, demonstrating a 1.5x to 3x increase in noise and 2.25x to 9x in impedance compared to in vitro measurements. Low frequency biological noise was also observed and studied through post mortem measurements. These results are informative for designing neural interfacing systems for both neuroscience and medical applications.
A Comparison of Solid, Mesh, and Segmented Strip Dipoles in a Subdermal Environment
Read Description
Simulations and measurements were used to evaluate the current distributions that are shared between antennas with and without voids (solid, segmented, and meshed strip dipole antennas) and surrounding body tissues to give insight into the performance of subdermal antennas and their coupling to the body. The body tissues play a strong role in adapting the current distributions. The high dielectric materials electrically shorten the antenna. The high conductivity muscle conducts or guides current into the body. Any voids in the antennas (e.g. gaps between segments or holes in the mesh) are particularly important, as they generate stronger coupling to the tissues. The feasibility of using fat as insulation is verified in simulation and confirmed with measurement.
Magnetic Targeted Drug Delivery to the Human Eye Retina: an Optimization Methodology
Read Description
In this paper we demonstrate how a system of magnets can be optimized to provide the maximal magnitude of the magnetic field gradient with a prescribed orientation in an extended area (vitreous body). The presented methodology is applicable for all tasks involving a magnetic targeted drug delivery to biological objects.
Deep transcranial magnetic stimulation for the addiction treatment: Electric field distribution modeling
Read Description
Recent clinical studies have focused on the use of H4 coils, which utilizes a left-right symmetric structure for bilateral stimulation of the prefrontal cortex, and demonstrated efficacy for therapy such as smoking cessation. The mechanism of activity, however, remains poorly understood, in part because the affected regions of the brain are not known in detail. To this purpose, computational techniques applied to highly detailed inhomogeneous tissue phantoms, provide a powerful tool for testing coil efficacy. In this work we quantified both electric field E distribution and its penetration depth in the prefrontal cortex, induced by a specific Hesed-coil, H4, designed for the addiction treatment and by the traditional figure-of-8 coil for comparison. Results show that H4 coil preferentially targets insula and cingulate cortex. Moreover, it can induce in the deepest tissues E amplitude ranging between the 20-40% of the cortical peak and it can penetrate the cortex up to 4 cm with a E>50% of the cortical peak, thus noticeably increasing the penetration depth of the traditional TMS systems.
A Near Field Cloaking Study to Reduce MRI RF-Artefacts in Presence of Elongated Prostheses
Read Description
The theoretical assumptions are proved by means of full-wave simulations that are also applied to a realistic hip prosthesis considering a frequency equal to 64 MHz and 128 MHz. Results: The numerical results confirm the theoretical assumptions. Both the theoretical analysis and the numerical simulations highlight the different role that the coat thickness and electric permittivity have in the definition of a proper dielectric coat. Clinical or Biological Impact: A particular cloaking approach leads to a dielectric coat whose constitutive electrical parameters may be simple enough to fit the considered application reducing the interaction between an elongated prosthesis and the RF antenna. Furthermore, results obtained at 64 MHz suggest the possibility to employ an existing biocompatible material to achieve the envisaged purposes.
A Multi-Channel Passive Brain Implant for Wireless Neuropotential Monitoring
Read Description
The proposed system consists of an external interrogator and a neuro-recorder implanted inside the scalp. For operation, the interrogator sends a) a 2.4 GHz carrier signal to “turn on” the implant, and b) an infrared control signal for channel selection. The latter activates the desired channel via a photo-activated multiplexer. For this channel, the carrier signal is mixed with the neural signal ( fneuro ) to generate a 4.8GHz±fneuro modulated signal. The latter is then transmitted back to the interrogator. To verify the implant’s operation inside biological tissues, in−vitro measurements are presented using pig skin. Experimental results show that the proposed neuropotential recorder exhibits 20 μVpp sensitivity at all eight channels (viz. it can record any signal generated by the human brain). The system is also in compliance with the strictest Federal Communications Commission standards for patient safety. Notably, the proposed approach is scalable to a much higher number of channels. As such, the proposed.
