RESUMO
Transcranial magnetic stimulation (TMS) is increasingly applied in basic neuroscience while its field of usage for diagnosing and treating various neurological diseases broadens steadily. A TMS device generates a current pulse in the reach of several thousand ampére to produce a magnetic pulse which induces an electric field around neurons. This electric field, if high enough to depolarize the neuron membrane, generates an action potential at the neuron which travels down the neurons connected to it. The PLUSPULS TMS generates this magnetic pulse by pre-charging a pulse capacitor C with the voltage V C 0 and connecting it with a stimulation coil L . The oscillation of the resonance circuit is cut off after one period and is called a biphasic pulse. PLUSPULS is a high frequency stimulator with inter stimulus intervals (ISI) down to 1ms which enables different pulse protocols as paired pulse or quadri theta burst stimulation. A GUI on PC allows a flexible control of PLUSPULS with varying amplitudes and ISI in one burst. The modular hardware and the control via GUI on PC allows for an easier adjustment on requirements to come. The article provides design considerations, hardware, firmware and software to reconstruct a modular biphasic TMS with enhanced charging network to enable extended pulse protocols.
RESUMO
Low-field, mobile NMR systems are increasingly used across diverse fields, including medical diagnostics, food quality control, and forensics. The throughput and functionality of these systems, however, are limited due to their conventional single-channel detection: one NMR probe exclusively uses an NMR console at any given time. Under this design, multi-channel detection could only be accomplished by either serially accessing individual probes or stacking up multiple copies of NMR electronics; this approach still retains limitations such as long assay times and increased system complexity. Here we present a new scalable architecture, HERMES (hetero-nuclear resonance multichannel electronic system), for versatile, high-throughput NMR analyses. HERMES exploits the concept of software-defined radio by virtualizing NMR electronics in the digital domain. This strategy i) creates multiple NMR consoles without adding extra hardware; ii) acquires signals from multiple NMR channels in parallel; and iii) operates in wide frequency ranges. All of these functions could be realized on-demand in a single compact device. We interfaced HERMES with an array of NMR probes; the combined system simultaneously measured NMR relaxation from multiple samples and resolved spectra of hetero-nuclear spins (1H, 19F, 13C). For potential diagnostic uses, we applied the system to detect dengue fever and molecularly profile cancer cells through multi-channel protein assays. HERMES holds promise as a powerful analytical tool that enables rapid, reconfigurable, and parallel detection.
