New methods for optimizing parallel transmit/receive array coils to small field-of-view excitation for breast and cardiac MRI
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Date
2017
Authors
Wei, Pei-Shan
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Abstract
The top two leading causes of death in Canada are cancer and coronary artery diseases and put a huge financial burden on the health care system. The ultimate goal of the work in this thesis is to achieve higher spatial resolution and higher temporal resolution for breast and cardiac magnetic resonance imaging (MRI) to diagnose these diseases. To achieve this, we developed new methods to design radiofrequency (RF) arrays optimized for these purposes.
Our approach is to design an eight-channel array coil that is both transmit and receive, and could be used for both types of studies. We focused on optimizing the array for the application of small field-of-view (FOV) excitation, which allows zooming into a region-of-interest (ROI). For example, in breast imaging it is important to see the tumor margin; the signal coming from outside of the breasts is not important and may degrade the image quality. Thus, the FOV could be limited to just the breast tissue.
There are two main technical tasks that are addressed in this thesis: 1) the design and optimization of a parallel transmission breast and cardiac array coil and 2) the development of a RF pulse design method for optimizing small FOV excitation. The consideration of specific absorption rate (SAR) associated with patient safety is necessary and is investigated in vitro as part of the basis for in vivo studies in the future.
There are three innovative methods that we developed for transmit/receive array design: (i) evaluating and understanding the impact of inductive coupling in RF coil simulations, (ii) reducing excitation artifacts through RF pulse and coil design, and (iii) evaluating and understanding the impact of inductive coupling in SAR.
Overall, these innovative approaches, which have previously been overlooked in MRI research, provide important guidance for RF array design, RF pulse design, and patient safety when optimizing for small FOV excitation.
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Keywords
MRI, parallel transmit, RF coil design