IEEE transactions on bio-medical engineering
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IEEE Trans Biomed Eng · Jul 2007
Finite-difference modeling of the anisotropic electric fields generated by stimulating needles used for catheter placement.
The use of peripheral nerve blocks to control pain is an increasing practice. Many techniques include the use of stimulating needles to locate the nerve of interest. Though success rates are generally high, difficulties still exist. ⋯ A smaller needle first locates a nerve bundle, and then is withdrawn in favor of a second, larger needle used for injection. The distinct geometries of these needles are shown to generate different electric field distributions, and these differences may be responsible for failures of the second needle to elicit nerve stimulation when placed in the same location as the first. A 3-D finite-difference method has been employed to numerically calculate the electric field distributions for a commercial set of stimulating needles.
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IEEE Trans Biomed Eng · Jul 2007
Low-power transceiver analog front-end circuits for bidirectional high data rate wireless telemetry in medical endoscopy applications.
State-of-the-art endoscopy systems require electronics allowing for real-time, bidirectional data transfer. Proposed are 2.4-GHz low-power transceiver analog front-end circuits for bidirectional high data rate wireless telemetry in medical endoscopy applications. The prototype integrates a low-IF receiver analog front-end [low noise amplifier (LNA), double balanced down-converter, bandpass-filtered automatic gain controlled (AGC) loop and amplitude-shift keying (ASK) demodulator], and a direct up-conversion transmitter analog front-end [20-MHz IF phase-locked loop (PLL) with well-defined amplitude control circuit, ASK modulator, up-converter, and power amplifier] on a single chip together with an internal radio frequency oscillator and local oscillating (LO) buffers. ⋯ The measured sensitivity of the receiver analog front-end is -70 dBm with a data rate of 256 kbps, and the measured output power of the transmitter analog front-end could achieve -23 dBm with a data rate of 1 Mbps. The integrated circuit consumes a current of 6 mA in receiver mode and 5.6 mA in transmitter mode with a power supply of 2.5 V. This paper shows the feasibility of achieving the analog performance required by the wireless endoscopy capsule system in 0.25 microm CMOS.
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IEEE Trans Biomed Eng · Jul 2007
Neuronal network morphology and electrophysiologyof hippocampal neurons cultured on surface-treated multielectrode arrays.
Toward the development of biocompatible surfaces for implantable electrode arrays and the creation of patterned neuronal networks, the impact of select biochemical substrates [poly-D-lysine (PDL), polyornithine (PO), polyethylenimine (PEI), and a basement membrane extract (BM)] on network morphology and spontaneous electrophysiological activity of dissociated hippocampal neurons was investigated. Cultured in serum-free Neurobasal medium at 100 000 cells/cm(2), neurons attached to each substrate. PDL, PO, and PEI induced little or no neuronal clustering and process fasciculation, whereas the addition of BM promoted these features. ⋯ Synchronized bursting was highly correlated with neuronal clustering and process fasciculation. Spike amplitude was negatively correlated with thin branching which was most evident in neurons grown on PEI. These data indicate that factors, which influence adherence of neurons to surfaces, can profoundly impact both neuronal network morphology and electrophysiological activity in vitro.