Spin-spin relaxation time (T2) dependence in MR saturation- and inversion- recovery images

The intensities of regions of interest in saturation-recovery (SR) and inversion-recovery (IR) images obtained with a new magnetic resonance (MR) scanner were compared with theoretically expected results, using phantom materials that had been accurately characterized in a specialized MR spectrometer. The data revealed significant dependence on the spin-spin relaxation time (T2), which was not expected on the basis of a simple model. The cause of this T2 dependence is discussed. The appearance and contrast of certain tissues in IR and SR images may be different than expected on the basis of the simple model. The results indicate that caution is required in making general claims about the efficacy of specific MR techniques because of potential subtle differences in the way that even the most basic sequences are implemented on individual imaging devices.