Tissue relaxation time: in vivo field dependence.

Abstract

Relaxation times (T1 and T2) were measured in vivo in mongrel dogs at fields of 0.3, 0.5, 1.0, 1.35, and 1.5 tesla (T). T1 was measured using 9 values of inversion time ranging from 10 to 1280 ms T2 was measured with a 4-point multiple spin-echo sequence. Relaxation times were calculated for muscle, kidney cortex, spleen, and adipose tissue. T2 is independent of field. A linear fit to the field dependence of T1 yields slopes of 400-500 ms/T for tissues in which the primary source of protons is water. The lower slope of adipose (.apprx. 150 ms/T) reflects the different mechanism of spin-lattice relaxation of the -CH2 protons.