Tissue determinants of nuclear magnetic resonance relaxation times. Effect of water and collagen content in muscle and tendon.

Previous studies have suggested a possible relationship between tissue collagen content and nuclear magnetic resonance (NMR) relaxation times. To further investigate this relationship, we studied skeletal muscle, tendon, and the muscle/tendon transition area of normal gastrocnemius muscle from 10 dogs, and determined tissue water and collagen (hydroxyproline) content and NMR T1 and T2 relaxation times at 20 MHz. Water and hydroxyproline contents and T1 and T2 were significantly different among the three tissues. Both spin-lattice and spin-spin relaxation times were linearly related to tissue water content. A significant curvilinear inverse relationship between T1 and hydroxyproline (r2 = 0.93) and a significant inverse curvilinear relationship between T2 and hydroxyproline (r2 = 0.92) were found. Statistically controlling for hydroxy-proline concentration eliminated differences in T1 and T2 among the muscle, muscle/tendon transition, and tendon groups. Thus, NMR relaxation times of skeletal muscle and tendon appear to be influenced by both tissue water and collagen content.