title: Spectral decomposition of susceptibility artifacts for spectral-spatial radiofrequency pulse design.
abstract: Susceptibility induced signal loss is a limitation in gradient echo functional MRI. The through-plane artifact in axial slices is particularly problematic due to the inferior position of air cavities in the brain. Spectral-spatial radiofrequency pulses have recently been shown to reduce signal loss in a single excitation. The pulses were successfully demonstrated assuming a linear relationship between susceptibility gradient and frequency, however, the exact frequency and spatial distribution of the susceptibility gradient in the brain is unknown. We present a spiral spectroscopic imaging sequence with a time-shifted radiofrequency pulse that can spectrally decompose the through-plane susceptibility gradient for spectral-spatial radiofrequency pulse design. Maps of the through-plane susceptibility gradient as a function of frequency were generated for the human brain at 3T. We found that the linear relationship holds well for the whole brain with an optimal slope of -1.0 μT/m/Hz.
authors.affiliation: Department of Medicine, University of Hawaii John A. Burns School of Medicine, Honolulu, Hawaii 96813-2427, USA.
authors.forename: Cungeng
authors.initials: C
authors.lastname: Yang
authors.forename: Benedikt A
authors.initials: BA
authors.lastname: Poser
authors.forename: Weiran
authors.initials: W
authors.lastname: Deng
authors.forename: V Andrew
authors.initials: VA
authors.lastname: Stenger
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011846:Radio Waves; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity