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Respiration-Induced B0 Fluctuations in the Human Brain at 7 Tesla and its Spatial Distribution

Bo fluctuations in the human brain induced by susceptibility changes during respiration were studied at 7T. In FIDs measured after a single RF pulse, a Respiration Induced Resonance Offset (RIRO) with large amplitude was consistently detected although the amplitude varied from 1.45 Hz to 4 Hz between subjects. In transverse EPI images in the occipital lobe, the RIRO amplitude showed a monotonic increase along Z-axis toward the lungs. Dynamic 3D FLASH phase maps revealed that a previously published analytical model can describe the spatial distribution of RIRO accurately. Subsequent apparent motions in EPI series and correction strategies are discussed.