Benefits and pitfalls of keyhole imaging, especially in first-pass perfusion studies

A comparison of dynamic results of a multi-echo contrast-enhanced perfusion study obtained from a keyhole Imaging experiment and the results from low- resolution updates is presented. If, for each dynamic state, a separate ref erence image exists, high spatial resolution in the dynamic results can be preserved through keyhole imaging. if only one reference image can be used, the dynamic keyhole results still offer high spatial frequency content due to spatial phase discontinuities in the images, These often exist at the o utline of organs and result from the fat in connective tissues. If the basi c assumption of keyhole imaging, namely, that the relevant information Is c entered in kappa-space, is violated, as in T-2*-weighted gradient-echo imag es, keyhole imaging can lead to erroneous results even though the update im ages themselves seem to be free of any artifacts. (C) 2000 Wiley-Liss, Inc.