MAGNETNO POLJE V OKOLICI S PREVODNO PLOŠČO ZASTRTE TULJAVE ZA TRANSKRANIALNO MAGNETNO STIMULACIJO

SIMON, MATIJA (author), Križaj, Dejan (mentor)

Transkranialna magnetna stimulacija (TMS) je pomemben element neinvazivne stimulacije aksonov nevronskih celic v možganih. Za stimulacijo se uporablja veliko časovno spremenljivo magnetno polje, ki ob in v aksonu nevrona inducira električno poljsko jakost in s tem napetost, ki stimulira in aktivira povezane nevrone. V delu je bila raziskana problematika usmerjanja elektromagnetnega (EM) pulza v karseda majhno področje, in sicer na način zastiranja/usmerjanja magnetnega polja s pomočjo prevodne plošče z izvrtino [2]. Ta zaradi vrtinčnih tokov izriva spreminjajoče se magnetno polje. Eden od ciljev je bil izvesti primerjavo med realnim poskusom ter simulacijo zastiranja polja. Za detekcijo EM pulza je bila uporabljena zračna tuljava, na kateri je bil pomerjen časovni potek napetosti ter njenega odvoda. Ugotovljeno je bilo, da efekt fokusiranja ni bil tako opazen pri počasnem pulzu, uporabljenem v laboratoriju (reda 5ms), medtem ko je plošča pri višji frekvenci pulza (reda 150µs) ta pulz zastrla ter zmanjšala področje vpliva (fokus). V simulaciji zastiranja pulza so bili uporabljeni enaki pogoji kot v napravi TMS, ki je komercialno dostopna v medicinske namene. Tudi tukaj so rezultati pokazali zmanjšanje področja vpliva. V vseh primerih je zastiranje pulza s ploščo povečalo fokus, a hkrati zmanjšalo velikost gostote magnetnega polja. Zato je v delu vključen še faktor povečanja toka, s katerim lahko dosežemo enako gostoto magnetnega pretoka kot brez uporabljene prevodne plošče. V diplomski nalogi ni bilo raziskanih medicinskih vplivov TMS na telo. Diplomsko delo je sestavljeno iz naslednjih delov: 1. poizkusna meritev v laboratoriju s sestavljenimi deli, 2. meritev z uporabo komercialno dostopne naprave za transkranialno magnetno stimulacijo, 3. numerična simulacija učinkov elektromagnetnega pulza.

• Language: Slovenian
• Keywords: TMS, transkranialna magnetna stimulacija, pulz, fokusiranje, prevodna plošča, izvrtina
• Work type: Undergraduate thesis
• Organization: FE - Faculty of Electrical Engineering
• Year: 2015
• PID: 20.500.12556/RUL-30697
• Publication date in RUL: 15.04.2015

Secondary language

• Language: English
• Title: MAGNETIC FIELD OF A CURRENT COIL SCREENED BY A CONDUCTIVE PLATE FOR USE IN TRANSCRANIAL MAGNETIC STIMULATION

Abstract

A major part in non-invasive stimulation of neuron cells axons in the brain is transcranial magnetic stimulation (TMS). Strong changing magnetic fields are used to create electric field and induce electric voltage in and around neuron axons. In case the electric field is strong enough the induced voltage activates the axons and therefore stimulates neurons. In this work the problem of focusing electromagnetic (EM) pulse into an area as small as possible was introduced. A way of focusing/shielding magnetic field with conductive shield plate was already proposed in [2]. Due to eddy currents the shield plate is reducing the changing magnetic fields. Comparison of a simulated and a real model of shielding was one of the goals of this work. A search coil was used for detection of EM pulse. During EM pulse the course of an induced voltage and its derivative was recorded with oscilloscope. It was established that effect of focusing with a conductive plate was not as visible using slowly changing EM pulse (length of 5ms) as it was when laboratory equipment had been used. While using higher frequency of EM pulse, the shield plate was focusing pulse in smaller area. Later in computer simulations the same conditions were used as they were while using commercially available TMS device. In both cases the focusing of EM pulse was noticed. In all cases in general it was noticed that shielding EM pulse considerably lowered the magnetic flux density B. Therefore if we want to achieve the same magnetic flux density as without the conductive plate, a proportional raise of pulse current is needed. No research was done considering health and influence of TMS on human body. This work consists of three main parts: 1. Measurements testing in faculty laboratory. 2. Measurements using commercially available TMS device. 3. Numerical simulation of electromagnetic pulse effects.

• Keywords: transcranial magnetic stimulation, TMS, pulse, focus, conductive, shield plate, bore