Birdcage Coils for MRI: In Vivo Imaging of 35-Chlorine and 1-Hydrogen Nuclei

• Other Authors: Elumalai, Malathy (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Electrical engineering; Computer engineering
• Online Access: http://purl.flvc.org/fsu/fd/FSU_migr_etd-0566

In this thesis, three different RF coils were investigated for their application in Magnetic Resonance Imaging (MRI). We developed transmit/receive birdcage volume coils since they provide better B1 field homogeneity than other coils. Coils were developed for in vivo imaging of chlorine and hydrogen nuclei. Chlorine is a low γ nucleus, therefore its sensitivity is very low. The high field of 21.1 T at NHMFL was exploited in order to obtain better signal strength from chlorine. Also, a comparative study was conducted between the linear coil and the quadrature coil of chlorine. Quadrature excitation helps in increasing the RF power efficiency, and results in up to √2 improvement in signal-to-noise ratio. In this work, strategies are presented for tuning, matching and isolating the two ports. We developed a third coil for proton imaging which incorporated the sliding ring tuning mechanism. The principle of sliding ring is to provide distributed capacitance. This results in tuning across all legs which in turn helps to maintain the symmetry of the birdcage coil. The resonance and quality factor was measured for all the three coils when loaded with saline, oil and poly ethylene glycol (PEG) solutions. In vivo experiments were carried out in order to image phantoms and rats in the 21.1 T magnet. It was observed that the quadrature chlorine coil provided 1.18 times improvement in sensitivity when compared to the linear coil. The sliding ring coil for proton helped in preserving the symmetry; it offered better tuning range when compared to the fixed lumped element design. RF coils are critically important in the performance of MRI scanners. We believe that the studies conducted in this project are contributions toward obtaining better imaging systems. === A Thesis submitted to the Department of Electrical and Computer Engineering in partial fulfillment of the requirements for the degree of Master of Science. === Summer Semester, 2011. === June 29, 2011. === Birdcage coils, R, F In Vivo Imaging === Includes bibliographical references. === Simon Y. Foo, Professor Directing Thesis; William W. Brey, Professor Co-Directing Thesis; Petru Andrei, Committee Member; Rajendra K. Arora, Committee Member.