The availability of high field whole body MR systems operating at field of 3 Tesla (T) and above presents unique challenges and opportunities to the biomedical imaging community. Major MR system manufactures (General Electric, Siemens, and others) have been slow to introduce these high field systems and when they have ventured into the high field arena they have been reluctant to develop radio frequency (RF) coils for anything other than the human head. With a large institutional commitment to 3T MRI, and an NIH funded program project to investigate spinal cord injury and repair at the University of Florida, the applicants are most interested in obtaining high resolution images of the human spine at 3R. Currently, such spinal cord imaging is restricted to the 1.5T platform with its attendant limitations on signal to noise and hence spatial resolution. The applicants propose to develop transceive, quadrature phased array RF coils operating at 3T to address this need. The specific challenge faced with a 3T whole body MR system is that of designing RF coil systems which operate effectively with the available RF power (5 KW), the limits imposed by the FDA for specific absorption rate (SAR), and the physical dimension of the magnet clear bore (55 cm). The opportunity is one of providing the highest possible sign to noise (SNR) across a large region of interest (the human spinal cord) with acceptable homogeneity and maximum flexibility in terms of applicable pulse techniques. The applicants propose to design, build and test a several RF coils including a whole body transmission RF coil, a receive only phased array, and a transceive surface coil phased array. They hypothesize that the transceive surface coil phased array will provide the optimal performance for this application, but intend to evaluate the full range of solutions to this problem in order to test this hypothesis. The goal is to achieve a 100% improvement in SNR over available receive only phased array RF coils operating at 1.5T and to provide depth penetration to 6cm or grater across the region of the human spine with less than 20% ripple in B1 field homogeneity at the specified depth. In addition the applicants plan to achieve this goal without exceeding the peak power limitation of 5 KW or the SAR limit of 4 W/kg. They propose to evaluate all coil designs on the bench and in the magnetic under typical imaging protocols using phantoms and human volunteers.
| Caserta, Jim; Beck, Barbara L; Fitzsimmons, Jeffrey R (2004) Reduction of wave phenomena in high-field MRI experiments using absorbing layers. J Magn Reson 169:187-95 |
| Peterson, David M; Duensing, G Randy; Caserta, Jim et al. (2003) An MR transceive phased array designed for spinal cord imaging at 3 Tesla: preliminary investigations of spinal cord imaging at 3 T. Invest Radiol 38:428-35 |
