Chen, Ji2022-06-29May 20212021-05May 2021Portions of this document appear in: S. Song, J. Chen, T. Vaughan, D. Shrivastava et al. “In Vivo Radiofrequency Heating in High and Ultra-High Field MRI”, Hoboken, NJ, USA: Wiley; and in: S. Song et al., "Dual-Frequency High-Electric-Field Generator for MRI Safety Testing of Passive Implantable Medical Devices," in IEEE Transactions on Microwave Theory and Techniques, vol. 68, no. 12, pp. 5423-5431, Dec. 2020, doi: 10.1109/TMTT.2020.3030789; and in: S. Song, Y. Wang, J. Zheng, Q. Wang and J. Chen, "A Novel Device Model Validation System for 1.5 T and 3 T MRI Safety Assessment," 2019 Photonics & Electromagnetics Research Symposium (PIERS - Fall), 2019, pp. 1283-1287, doi: 10.1109/PIERS-Fall48861.2019.9021675.https://hdl.handle.net/10657/10191Magnetic resonance imaging (MRI) has become a widely used diagnostic method due to its unparalleled ability for soft tissue imagine. Although 1.5T MRI is still the most performed procedure in clinic, higher fields such as 3 T and 7 T are gaining more popularity because of their increased sensitivity and spatial resolution. However, the increased frequency caused the degradation of the field uniformity. To compensate the field distortion, a so-called RF shimming method is proposed. The tricky part of RF-shimming is that once the arbitrary excitation is applied, the induced special absorption rate (SAR) will be hard to predict, the most dangerous point, which has the highest SAR, will move around the whole-body area and SAR level will change quiet a lot, in Chapter 1, we studied the SAR and temperature level in different human bodies, under different exposure conditions; in Chapter 2, we applied the machine learning method to help us to predict the induced SAR location and level. And nowadays, there are increasing populations who has implantable medical devices (IMDs) who need to go under MRI scanning, especially for some patients, the treatment will need IMDs and MRI together, to investigate the interaction of the IMDs and the EM field, we designed a new test system, the design, the validation of the novel field generator and its application for passive IMDS is introduced in Chapter 3, the application on active IMDs, which has quite different methods, is included in Chapter 4.application/pdfengThe author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. UH Libraries has secured permission to reproduce any and all previously published materials contained in the work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).MRI safetyEM simulationradiator design2022-06-29Thesisborn digital