Application to Rat Lung of the Extended Rorschach–Hazlewood Model of Spin–Lattice Relaxation

The spin–lattice relaxation time T 1 was measured in excised degassed (airless) rat lungs over the frequency range 6.7 to 80.5 MHz. The observed frequency dependence was fitted successfully to the water–biopolymer cross-relaxation theory proposed by H. E. Rorschach and C. F. Hazlewood (RH) [ J. Magn. Reson. 70, 79 (1986)]. The rotating frame spin–lattice relaxation time T 1ρ was also measured in rat lung fragments over the frequency range 0.56 to 5.6 kHz, and the observed frequency dependence was explained with an extension of the RH model. The agreement between the theory and the experimental data in both cases is good.