Defense Date

2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Mechanical and Nuclear Engineering

First Advisor

Ravi Hadimani

Second Advisor

Karla Mossi

Third Advisor

Kathryn Holloway

Fourth Advisor

Reza Mohammadi

Fifth Advisor

Carrie Peterson

Abstract

Transcranial Magnetic Stimulation (TMS) is a non-invasive technique for diagnostics, prognostic, and treatments of various neurological diseases. However, the lack of anatomically realistic brain phantoms has made the experimental verification of stimulation strength in the form of induced electric fields/voltages in the brain tissues an impediment to developing new TMS coils, stimulators, and treatment protocols. There are significant technological, safety, and ethical limitations to test the potential TMS treatment procedures or develop enhancements and refine them on humans or animals. This work aims to bridge the gap by introducing and developing an innovative manufacturing and fabrications process to produce a geometrically and anatomically accurate head and brain phantom capable of being used in experimental evaluations of stimulation strengths in neuromodulation techniques and in particular in TMS. We developed a 3-D anatomically accurate brain phantom that can mimic the electrical conductivity of the brain by first developing a process of creating computational 3D models using patient-specific MRIs followed by the development of a polymer composite that mimics the brain’s conductivity and finally, a process to covert computational 3D models to patient-specific anatomically accurate brain phantoms. We present the development and fabrication processes of the head and brain phantom in detail. The process is based on our novel technique called “the shelling method” that enables the production of highly intricate geometries like the brain. After that, we show an example of the current and immediate application of this research in which the brain phantom can play an essential role in developing new TMS treatment procedures for neurological disorders. We use the brain phantom to examine the safety of combing two of the prominent brain stimulation techniques, TMS and DBS. Our experiment on the phantom shows that It is unsafe to operate the TMS joined with the DBS when operated at maximum and proximal to the DBS leads. Moreover, we run a series of experiments and measurements to assess and evaluate the brain phantom’s stimulation strengths during TMS. We also present the measured magnetic fields generated by the TMS coils in the Biomagnetics Laboratory. We investigated the feasibility of mapping the electric field on the brain using anatomically accurate brain phantoms. Finally, we conclude our work and recommend future improvements to the patient-specific, anatomically accurate brain phantom.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

10-22-2020

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