Improvements in signal to noise ratio (SNR) and ease of use of magnetic resonance imaging (MRI) rf coils are needed to improve image quality and patient throughput. The goal of this Phase I project is to develop a novel rf coil topology that promises substantially improved technical performance, reduced cost, and greatly simplified tuning procedures. Advanced, proprietary, simulation software and coil technology permits the design of coils that utilize both paralleled conductor elements with insulated crossovers and segmented phase shifts to achieve circular polarization with improved homogeneity in an easily tunable structure. We expect to demonstrate feasibility of a quadrature, semi-shielded, passively shimmed rf litz coil with suppressed axial flux and an asymmetric axial field profile. The Phase I effort will see the completion and bench testing of a coil for human head MRI at 3 T. The rf shield is expected to reduce radiation losses by two orders of magnitude compared to the unshielded birdcage and permit maximum access to the patient's head for visual and auditory stimulation protocols. Tune-up time will be reduced by more than an order of magnitude. Light-load (small patient) SNR is expected to exceed that of conventional birdcages by about 4 dB, equivalent to 60 percent reduction in image acquisition time. The design will be compatible with EPI (Echo Planar Imaging) and will be suitable for use from 1 to 5 T. Field testing is expected at the beginning of Phase II at the Massachusetts General Hospital. The Phase II will continue with the development of quadrature Iitz coils for head, knee, heart, and neck. The objective is to permit a substantial increase in MRI patient throughput (thereby reducing scan costs) via relatively inexpensive upgrades of head, knee, heart, and neck rf coils in existing high-field MRI scanners and/or enable the more detailed diagnostic studies that are currently not practical because image acquisition time would be excessive.
There are approximately 12,000 MRI systems installed world-wide, and annual equipment sales are currently about $3B. The proposed rf head coil would permit substantially improved image resolution, reduced imaging time (hence, cost), and reduced patient distress for head imaging in most high field MRI scanners above 0.8 T at the relatively modest upgrade cost of $30,000 to $50,000, depending on field. Total upgrade market potential over the decade following completion of the Phase II exceeds $40M.
