Automatic field map generation and off-resonance correction for projectionreconstruction imaging

A new projection reconstruction technique utilizes the oversampling of low spatial frequencies to estimate and correct for off-resonance effects. Inte rleaved spokes are acquired at one of two different echo times. From separa ted early-TE and late-TE raw data, two one-quarter resolution images are re constructed and a one-quarter resolution field map is computed, Multifreque ncy reconstruction with all the data is then used to simultaneously correct for off-resonance and compensate for the difference in echo times. Resulti ng images obtained on phantoms and in vivo demonstrate significantly reduce d off-resonance artifact without the acquisition of a separate field map. M agn Reson Med 43:151-154, 2000, (C) 2000 Wiley-Liss, Inc.