Work has continued on planning for the arrival of the 11.7T magnet (now slated to be shipped back to NIH in October), with particular emphasis on human safety aspects. Test objects have been designed to allow measurement of tissue heating associated with MRI signal generation, and a prototype, single radiofrequency (RF) transmitter channel with on-coil signal amplification has been tested as part of the construction of a transmit array that will overcome some of the anticipated difficulties in MRI signal generation in deep brain areas. A whole-brain transmit coil is nearing completion and has been demonstrated to allow nearly uniform RF transmit fields even when driven from a single RF channel. Although much of this uniformity will be lost when imaging human brain, the coil will provide a good starting point for imaging superficial areas of the brain, in particular when combined with surface coil signal reception. A novel technique to measure brain myelin content has been developed and tested at 3T and 7T. The method uses low levels of RF compared to existing methods and will therefore be applicable at 11.7T, where it will provide improved sensitivity. Measurements on brain tissues and life marmosets are underway to establish the methods specificity to myelin as well as, more generally, to help understand the contributions of myelin to MRI contrast at high field.
| Gudino, Natalia; de Zwart, Jacco A; Duan, Qi et al. (2018) Optically controlled on-coil amplifier with RF monitoring feedback. Magn Reson Med 79:2833-2841 |
| Liu, Jiaen; de Zwart, Jacco A; van Gelderen, Peter et al. (2018) Effect of head motion on MRI B0 field distribution. Magn Reson Med 80:2538-2548 |
| van Gelderen, Peter; Jiang, Xu; Duyn, Jeff H (2017) Rapid measurement of brain macromolecular proton fraction with transient saturation transfer MRI. Magn Reson Med 77:2174-2185 |
| Jiang, Xu; van Gelderen, Peter; Duyn, Jeff H (2017) Spectral characteristics of semisolid protons in human brain white matter at 7 T. Magn Reson Med 78:1950-1958 |
| Gudino, Natalia; Duan, Qi; de Zwart, Jacco A et al. (2016) Optically controlled switch-mode current-source amplifiers for on-coil implementation in high-field parallel transmission. Magn Reson Med 76:340-9 |
| Duan, Qi; Nair, Govind; Gudino, Natalia et al. (2015) A 7T spine array based on electric dipole transmitters. Magn Reson Med 74:1189-97 |
| van Gelderen, Peter; Mandelkow, Hendrik; de Zwart, Jacco A et al. (2015) A torque balance measurement of anisotropy of the magnetic susceptibility in white matter. Magn Reson Med 74:1388-96 |
| Duan, Qi; Duyn, Jeff H; Gudino, Natalia et al. (2014) Characterization of a dielectric phantom for high-field magnetic resonance imaging applications. Med Phys 41:102303 |
| Duyn, Jeff H (2014) Frequency shifts in the myelin water compartment. Magn Reson Med 71:1953-5 |
| Duyn, Jeff H; Barbara, Thomas M (2014) Sphere of Lorentz and demagnetization factors in white matter. Magn Reson Med 72:1-3 |
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