Artifacts in T1ρ-weighted imaging:: correction with a self-compensating spin-locking pulse

Significant artifacts arise in T-1rho-weighted imaging when nutation angles suffer small deviations from their expected values. These artifacts vary with spin-locking time and amplitude, severely limiting attempts to perform quantitative imaging or measurement of T-1rho relaxation times. A theoretical model explaining the origin of these artifacts is presented in the context of a T-1rho-prepared fast spin-echo imaging sequence. Experimentally obtained artifacts are compared to those predicted by theory and related to B-1 inhomogeneity. Finally, a "self-compensating" spin-locking preparatory pulse cluster is presented, in which the second half of the spin-locking pulse is phase-shifted by 180degrees. Use of this pulse sequence maintains relatively uniform signal intensity despite large variations in flip angle, greatly reducing artifacts in T-1rho-weighted imaging. (C) 2003 Elsevier Science (USA). All rights reserved.