NMR imaging of spin-lattice relaxation using stimulated echoes

Abstract

Abstract A new NMR imaging technique is presented which allows a detailed determination of the spin-lattice relaxation behavior. Both the spatial resolution and the measuring time are the same as for a conventional NMR image. The experiment yields a series of cross-sectional images with intensities declining according to the T1 relaxation curve. The technique is based on the principles of stimulated-echo acquisition-mode (STEAM) imaging which have been described in a preceding paper. For T1 imaging the final 90° rf pulse of the basic three-pulse STEAM imaging sequence is split into a variable number of small-angle rf pulses. Each of these pulses should read out the same amount of the longitudinal magnetization which has been prepared by the two leading 90° pulses. They give rise to a series of stimulated echoes with a T1 weighting which depends on the length of the interval between the second 90° pulse and the readout pulse. STEAM T1, imaging is characterized by an extremely low rf power deposition and, therefore, will be suitable for high-field NMR imaging. The method is easily extended to multislice measurements as well as to chemical-shift-selective (CHESS) T1 imaging. 1H NMR images have been obtained at 100 MHz using a 2.3 T magnet with a bore of 40 cm.