title: Sodium imaging of human brain at 7 T with 15-channel array coil.
abstract: Signal-to-noise ratio (SNR) is a major challenge to sodium magnetic resonance imaging. Phased array coils have been shown significantly improving SNR in proton imaging over volume coils. This study investigates SNR advantage of a 15-channel array head coil (birdcage volume coil for transmit/receive and 15-channel array insert for receive-only) in sodium imaging at 7 T. Phantoms and healthy human brains were scanned on a whole-body 7 T magnetic resonance imaging scanner using a customer-developed pulse sequence with the twisted projection imaging trajectory. Noise-only images were acquired with blanked radiofrequency excitations for noise measurement on a pixel basis. SNR was calculated on the root of sum-of-squares images. When compared with the volume coil, the 15-channel array produced SNR more than doubled at the periphery and slightly increased at the center of the phantoms and human brains. Decorrelation of noise across channels of the array coil extended the SNR-doubled region into deep area of the brain. The spatial modulation of element sensitivities on the sum-of-squares combined image was removed by performing self-calibrated sensitivity encoding parallel image reconstruction and uniform image intensity across entire field of view was attained. The 15-channel array coil is an efficient tool to substantially improve SNR in sodium imaging on human brain.
authors.affiliation: MR Research Center, Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA. qiany@upmc.edu
authors.forename: Yongxian
authors.initials: Y
authors.lastname: Qian
authors.forename: Tiejun
authors.initials: T
authors.lastname: Zhao
authors.forename: Graham C
authors.initials: GC
authors.lastname: Wiggins
authors.forename: Lawrence L
authors.initials: LL
authors.lastname: Wald
authors.forename: Hai
authors.initials: H
authors.lastname: Zheng
authors.forename: Jonathan
authors.initials: J
authors.lastname: Weimer
authors.forename: Fernando E
authors.initials: FE
authors.lastname: Boada
mesh_terms: D001921:Brain / Q000033:anatomy & histology; D001923:Brain Chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D057054:Molecular Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012964:Sodium / Q000032:analysis*; D014018:Tissue Distribution; D014159:Transducers
chemical_list: D012964:Sodium