Correction of errors caused by imperfect inversion pulses in MR imaging measurement of T1 relaxation times

Spin-lattice (T-1) relaxation times were measured by an inversion-recovery magnetic resonance imaging method with a slice-selective inversion pulse (SIP), a non-selective rectangular inversion pulse (RIP), or a B-1-insensitive adiabatic inversion pulse (AIP), Data analysis either assumed perfect inversion (two-parameter fit) or allowed for imperfect inversion (three-parameter fit), Imperfect inversion pulses caused low T-1 values in phantoms with a two-parameter fit, while three-parameter T-1 estimates were accurate over the range 430-2670 ms. A difference of similar to 10% between two-parameter and three-parameter T-1 values in normal human brain tissue was attributed to B-1 inhomogeneity with the slice-selective inversion pulse and rectangular inversion pulse, to the slice profile with the slice-selective inversion pulse, and to T-2 effects for the adiabatic inversion pulse. Any T-1 method that relies on accurate flip angles may have a significant systematic error in vivo. Phantom accuracy does not ensure accuracy in vivo, because phantoms may have a more homogeneous B-1 field and a longer T-2 than do biological samples. (C) 1998 Elsevier Science Inc.