This project will design, construct, and evaluate a prototype novel gradient array system for extended field of view imaging in magnetic resonance imaging. The gradient design consists of novel repetitions of the longitudinal and transverse gradients to create multiple non-adjacent imaging regions. Imaging is performed in the regions where the applied field gradients are linear. Just as the Maxwell pair (composed of two coaxial coils with alternating currents) can be used to generate a Z-gradient to perform imaging over one region, a Maxwell triplet (composed of three coils with alternating currents) might be used to perform image acquisition over 2 non-contiguous regions of linear field variation and thereby improve imaging efficiency. To acquire image data from the central region of non-linear field variation requires a 2nd Maxwell array which overlaps with the first array such that the linear region(s) of the 2nd array are positioned over the central non-linear I region of the first array. Transverse gradient arrays for multiple region imaging will be designed in a similar manner. In the R21 phase we will use numerical methods and computer simulations to investigate the design and predict the performance of such gradient arrays, including efficiency, slew rate, homogeneity, and power requirements as a function of current distribution. We will also study the issues of gradient overlap, transmit and receive RF coils, and pulse sequence design to obtain contiguous imaging regions. In the R33 phase, we will use the designs from the R21 phase to construct a prototype insert gradient system and the RF coils required for multiple region imaging. We will test the gradient arrays and RF coils at various stages of production. We will also construct a whole-body composite gradient array and perform detailed nerve stimulation studies. This novel design will allow complete utilization of all existing high performance pulse sequences. It will also allow the development of new pulse sequences that utilize the complete hardware capabilities to simultaneously attain increased gradient performance, increased imaging field of view, and decreased nerve stimulation.
|Moon, Sung M; Goodrich, K Craig; Hadley, J Rock et al. (2011) Superelliptical insert gradient coil with a field-modifying layer for breast imaging. Magn Reson Med 65:863-72|
|Parker, Dennis L; Goodrich, K Craig; Hadley, J Rock et al. (2009) Magnetic Resonance Imaging with Composite (Dual) Gradients. Concepts Magn Reson Part B Magn Reson Eng 35:89-97|
|Goodrich, K Craig; Hadley, J Rock; Moon, Sung M et al. (2009) Design, Fabrication and Testing of an Insertable Double-Imaging-Region Gradient Coil. Concepts Magn Reson Part B Magn Reson Eng 35B:98-105|