Adiabatic RARE imaging

The practical implementation of ultra‐fast spin‐echo, or RARE imaging with adiabatic RF pulses and surface coil transmission at 7 T is described. Despite the large RF inhomogeneities, the adiabatic character of the 180° BIR‐4 refocusing pulses ensures optimal sensitivity and minimal image artifacts. An internal ‘phase‐cycle’ is used to remove spurious unwanted coherences. The short T 2 relaxation times in rat brain at 7 T demand a centric, rather than a linear coverage of k ‐space in order to avoid excessive signal loss. T 2 relaxation during k ‐space coverage also leads to image blurring, which can be counteracted by interleaved k ‐space sampling. The coverage of k ‐space in four acquisitions provides high‐quality anatomical images comparable to conventional spin‐echo images. A two‐scan RARE implementation provides sufficient spatial and temporal resolution for most applications. Quantitative mapping of T 1 relaxation and cerebral blood flow changes during forepaw stimulation in the rat are demonstrated. Copyright © 2003 John Wiley & Sons, Ltd.