T-one insensitive steady state imaging: A framework for purely T2-weighted TrueFISP

A new conceptual framework called T-one insensitive steady state imaging is proposed for fast generation of MR images with pure T2 contrast. This is accomplished by imaging between nonequally spaced inversion pulses, with the magnetization vector alternatively residing in states parallel and antiparallel to B0 for durations TPi and TAi, respectively. With TPi and TAi adequately chosen, identical signal time evolution can be obtained for different T1 values, i.e., T1 contrast can efficiently be removed from resultant images. As a specific realization of this principle, T-one insensitive steady state imaging sequences are presented which use True free induction steady precession readout blocks between the inversion pulses. While the conventional True free induction steady precession signal time course would be determined by both T2 and T1, a pure T2 dependence is realized with successfully suppressed influence of longitudinal relaxation, and images with essentially T2 contrast alone are obtained. Analytical expressions are provided for the description of the ideal signal behavior, which help in creating pathways for sequence parameter optimization. The performance of the technique is analyzed with Bloch equation simulations. In vivo results obtained in healthy volunteers and brain tumor patients are presented. Magn Reson Med, 2012. (C) 2011 Wiley Periodicals, Inc.