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OPTIMIZING RF AND GRADIENT COILS IN MRI

Yao, Zhen
http://rave.ohiolink.edu/etdc/view?acc_num=case1402058570

Abstract Details

2014, Doctor of Philosophy, Case Western Reserve University, Physics.
In this dissertation, several topics on gradient and RF coils in MRI system are studied. Chapter 1 provides an introduction to basics of MRI. Chapter 2 and Chapter 3 focus on methods of eddy current and heat calculation induced by a gradient coil system. A strip model is studied in detail, and effective ways to suppress the heating on the strip are found which serves as a basis for Chapter 4. In chapter 4, guidelines are provided for optimizing slit patterns in radio-frequency (RF) shields. In Chapter 5, acoustic noise induced by gradient system is studied; an acoustic suppression model with modifications of sequence shape is applied, whereby one can suppress several significant vibration modes in kHz range. In Chapter 6, we investigated RF induced heating effect with FDTD simulations. A model for a guidewire inside a plate phantom is studied in detail. Pronounced heating effect is found close to the tip of the guidewire. Specific absorption rate (SAR) levels are calculated for 6 different phase configurations, and compared with both quasi-static calculations and temperature measurements. We found that the quasi-static calculation can serve as an efficient and rapidly applied temperature guide, which can be integrated into a quadratic xxi optimization algorithm for the suppression of the RF induced heating effect. In Chapter 7, noise correlations between different RF phased-array channels are studied. Both quasi-static and FEM full-wave simulations are performed to show the inaccuracy of quasi-static calculation. A simple model for calculating the noise correlation between RF receiver coils is proposed and tested. We find out that the two correlation mechanisms correspond to the resistive and reactive parts of inductive voltage, respectively. This method offers a convenient way of carrying out noise correlation calculations for RF receiver coils (surface or volume) without performing electric field integrations over the whole sample.
Robert Brown (Committee Chair)
Michael Martens (Committee Member)
Mark Griswold (Committee Member)
Weihong Guo (Committee Member)
Shmaryu Shvartsman (Committee Member)
155 p.
Medical Imaging; Physics

Recommended Citations

Citations

  • Yao, Z. (2014). OPTIMIZING RF AND GRADIENT COILS IN MRI [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1402058570

    APA Style (7th edition)

  • Yao, Zhen. OPTIMIZING RF AND GRADIENT COILS IN MRI. 2014. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1402058570.

    MLA Style (8th edition)

  • Yao, Zhen. "OPTIMIZING RF AND GRADIENT COILS IN MRI." Doctoral dissertation, Case Western Reserve University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1402058570

    Chicago Manual of Style (17th edition)

case1402058570
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© 2014, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.