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 II project is to continue the development of novel rf coil topologies and rf balancing circuits that have demonstrated substantially improved technical performance, reduced cost, and greatly simplified tuning procedures. The success of the Phase I effort demonstrated the unique contributions possible with our advanced, proprietary, simulation software and patented coil technology. The circular polarization (CP) coils built and tested during Phase I demonstrated an improvement of a factor of 3 to 15 (depending on the reference CP technology) in tunability (ability to tune and match efficiently over a wide range of sample loading conditions at very high fields) for equivalent BI homogeneity. Also, much higher B1 homogeneity is maintained over the full range of load conditions. Substantial improvements were also achieved in signal to noise ratio (SNR) and passive Bo shimming, and further gains are expected here during Phase II. We denote these coils """"""""litzcages"""""""", as they embody both paralleled conductor elements with insulated crossovers similar to that in our prior """"""""litz coil"""""""" technology and capacitively segmented phase shifts and four-point drive to achieve highly stable circular polarization. We have demonstrated feasibility of a quadrature, single-tuned, semi-open, passively shimmed rf litzcage with an axially asymmetric field profile. The Phase I saw the development and bench testing of numerous linear and CP litz coils, including one for human knee studies at 3 to 6 T, one for small-animal research at 500 MHz, one for single-resonance human head MRI at 3-4 T, and one for double-resonance human head MRI at 1.5 T. The Phase II will continue with the development and field testing of quadrature single-resonance litzcages optimized for human head, knee, neck, and torso at 3-7 T, as well as smaller CP litzcages for animal research at the highest fields. Preliminary development of a 3 T double-resonance multinuclear 'HM head coil utilizing our linear litz coils is also planned. The primary objective is to permit a substantial increase in MRI patient throughput (thereby reducing scan costs) via relatively inexpensive upgrades of head, knee, neck, and torso rf coils in existing high-field MRI scanners and/or to enable the more detailed diagnostic studies that are currently not practical because image acquisition time would be excessive. Field testing of a 3 T 'H head coil and a 3 T knee coil will begin early in Phase II at the Hershey Medical Center, Hershey, PA. The FDA approval process for head, knee, and neck coils will also begin during the Phase II.
| Doty, F David; Entzminger, George; Kulkarni, Jatin et al. (2007) Radio frequency coil technology for small-animal MRI. NMR Biomed 20:304-25 |
