Dispersion of proton spin-lattice relaxation in tissues

Abstract

The dispersion of the proton spin-lattice relaxation time was measured for selected mouse tissue in the laboratory ( T 1) and rotating ( T 1 ϱ ) frames at 25°C. These measurements covered the 17–45 MHz and 10 3–10 5 kHz (from H 1 = 0.25–25 G) ranges, respectively. If it is assumed that molecular and atomic motions with discrete correlation times are responsible for the observed relaxation, two correlation times and a region of mostly free water are required to characterize the results. The correlation times for the exchange of protons and for the rotation of water molecules at 25°C were found to be approximately 7 × 10 −6 and 2 × 10 −8 sec, respectively. The fast processes relaxing the free water have the correlation time less than ∼10 −10 sec.