Overview: The primary goal of this project is to improve the training of university students in the design of specialized RF coils and their associated RF circuitry. As such, the project had to remain flexible, as the objectives of our industry partner (GE Medical Systems) needed to be met as well.
Three major areas of research were defined in the original proposal:
A) Optimization of Array Coils for Parallel Imaging.
The goal of this project was to develop optimized array coils which provide maximal image speed reduction over the largest possible FOV. This was pursued by several of the student participants during the project, as denoted in the project activities and findings.
B) Multiplexed Detectors.
The goal of this project was to develop improved TDM techniques which reduce or eliminate present restrictions on sequence bandwidth and numbers of array elements. An unanticipated development during this project was that the number of available receivers grew significantly, rendering the use of multiplexing, for at least the time being, unnecessary. All array coils used in this project used dedicated receivers.
C) Desktop MRI Systems.
The goal of this project was to use commercially available RF technology to further develop and optimize a MR scanner and to improve SNR/unit time through the use of a variety of RF technologies.
The following is the description of the various projects that were done to fulfill the proposed goals.
Project 1: At high field MRI, the RF excitation field (B1) becomes inhomogeneous. This provides a challenge in designing RF transmit coils for uniform filed excitation. We have investigated RF current element design for independent control of current amplitude and phase in transmit phase arrays to provide uniform B1 field patterns (Krishna Kurpad). (Goal A)
Project 2. Development and Application of a FDTD simulator for RF coils for MRI. (Jason Payne) (Goal A)
Project 3. Design and development of a RF power amplifier for transmit array coils in MRI and investigating the cable effects on ability of reducing coupling effects of a RF current source amplifier (Hyokwon Nam) (Goal A)
Project 4: 16 element head coil was designed for accelerated brain imaging. (Nabeel Malik) ( Goal A)
Project 5: With an increasing number of receiver channels in parallel imaging, there is a corresponding increase in the amount of data that needs to be processed. This translates to a few hours of time gap between the data acquisition and image visualization. We addressed this problem by building a data processing and reconstruction system consisting of state-of-the-art digitizers and signal processors in one single computer (Naresh Yallapragada) (Goal C).
Project 6: Array SNR as a function of Preamplifier Decoupling Quality (Bijay and Ke) (Goal A)
Project 7: MR Hardware Enhancement (Ke Feng) (Goals A and C)
Project 8: Coil design and development
· Coil designs for various purposes were carried out by the participants while interning at GE. The most prominent ones are listed below:
· We have developed a coil capable of producing high resolution images while keeping high SNR at the site of carotid bifurcation which is approximately 3.5 cm away from the surface of neck. We developed 2,4,6 and 8 channel coils of different sizes and shapes and compared the SNR at 3.5 cm from the surface of the coil. We found that three 3” circular loop on each side of the neck gave the highest performance. (Susan Mathew)
· 16 channel pelvic coil array was developed at 7T. (Colleen Dominick)
· Double tuned 3T birdcage and surface coils (proton and carbon imaging) (X Liu)
· 3T, 7T birdcage mice coil with 16 rungs (X Liu)
· Surface coil of radius 1 inch at 3T and 1.5T (X Liu).