<p> The purpose of this thesis was to design, build and test a prototype artifact suppressing electroencephalogram data acquisition system (AS-EEG-DAQ-S) to collect electroencephalogram (EEG) evoked potential (EP) data during repetitive transcranial magnetic stimulation (rTMS) without the EEG signal being masked by transcranial magnetic stimulation (TMS) artifact. A functional AS-EEG-DAQ-S capable of blocking TMS artifact would provide for the first time a quantitative measurement system to assist in optimal TMS coil positioning during the rTMS treatment of depression, an alternative to electroconvulsive therapy (ECT). This thesis provides the details for an AS-EEGDAQ-S. Preliminary TMS EP results on a human subject were collected. Results showed transcallosal conduction times of 12ms to 31ms, which are consistent with those predicted and collected by other researchers in the TMS field. </p> <p> The first portion of this work provides electrode heating data for modem rTMS Paradigms for the recording ofEEG during rTMS. The concern is that during rTMS EEG electrodes can heat to an unsafe temperature. Seven electrode types were tested: silver/silver chloride, silver cup, gold cup, notched gold cup, notched silver cup, notched gold-plated silver cup, and carbon. All electrodes tested are commercially available, including the carbon electrodes designed for MRI use. The three notched electrodes tested were standard electrodes notched using metal clippers to reduce induced currents. Induced currents are responsible for electrode heating during rTMS and can cause burns to the skin. The results ,of this study show that electrode heating is a concern when collecting BEG during rTMS. However, a number of standard electrodes or slightly modified standard electrodes are suitable for recording BEG during rTMS if certain stimulating parameters are adhered to. </p> <p> The second portion of this work provides the detailed development and design of the AS-EEG-DAQ-S. Four different approaches were tested and their ability to withstand a TMS pulse compared. </p> <p> Short circuiting the input pins of a commercially available EEG amplifier was the first approach tried and yielded only marginal results due to the switches used being designed for digital logic, transistor built, and creating an undesirable offset between input pins. </p> <p> The second approach tested involved continuing to work with a commercially available EEG amplifier and implementing a sample-and-hold circuit between the patient and the EEG machine inputs. This approach had the drawback of requiring that the BEG signal be attenuated back to EEG signal levels, which are near noise amplitude levels. </p> <p> The third approach involved using a high bandwidth amplification circuit to recover quicker from the baseline voltage offset created by the TMS artifact. However, increasing the bandwidth also allows the artifact to saturate the input amplifiers, which then require on the order of 500ms to recover fully. </p> <p> The fourth approach involved combining the second and third approaches to create a high bandwidth amplifier that incorporates a sample-and-hold circuit to prevent amplifier saturation when gain is increased. The fourth approach provide the high bandwidth and artifact blocking behavior desired. </p> / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/21937 |
| Date | 08 1900 |
| Creators | Archambeault, Mark |
| Contributors | de Bruin, H., Electrical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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