13 May 2015 Sensor probes and phantoms for advanced transcranial magnetic stimulation system developments
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Transcranial magnetic stimulation (TMS) has become one of the most widely used noninvasive method for brain tissue stimulation and has been used as a treatment tool for various neurological and psychiatric disorders including migraine, stroke, Parkinson's disease, dystonia, tinnitus and depression. In the process of developing advanced TMS deep brain stimulation tools, we need first to develop field measurement devices like sensory probes and brain phantoms, which can be used to calibrate the TMS systems. Currently there are commercially available DC magnetic or electric filed measurement sensors, but there is no instrument to measure transient fields. In our study, we used a commercial figure-8 shaped TMS coil to generate transient magnetic field and followed induced field and current. The coil was driven by power amplified signal from a pulse generator with tunable pulse rate, amplitude, and duration. In order to obtain a 3D plot of induced vector electric field, many types of probes were designed to detect single component of electric-field vectors along x, y and z axis in the space around TMS coil. We found that resistor probes has an optimized signal-to-noise ratio (SNR) near 3k ohm but it signal output is too weak compared with other techniques. We also found that inductor probes can have very high output for Curl E measurement, but it is not the E-field distribution we are interested in. Probes with electrical wire wrapped around iron coil can directly measure induced E-field with high sensitivity, which matched computer simulation results.
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Qinglei Meng, Qinglei Meng, Prashil Patel, Prashil Patel, Sudhir Trivedi, Sudhir Trivedi, Xiaoming Du, Xiaoming Du, Elliot Hong, Elliot Hong, Fow-Sen Choa, Fow-Sen Choa, "Sensor probes and phantoms for advanced transcranial magnetic stimulation system developments", Proc. SPIE 9487, Smart Biomedical and Physiological Sensor Technology XII, 94870W (13 May 2015); doi: 10.1117/12.2177014; https://doi.org/10.1117/12.2177014

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