Nuclear magnetic resonance (NMR) relaxation spectroscopy in tissues.

Nuclear magnetic resonance (NMR) techniques have been used to study several in vivo and stabilized tissue samples. The results show that a multicomponent behavior characterizes the magnetization relaxation of all investigated samples. Various specimens were allowed to undergo necrotic processes and then they were examined with the same techniques used in in vivo tissue. A marked approach toward a single-exponential magnetization-decay behavior was observed in these necrotic samples. In addition, large and sometimes irreversible temperature variations have been observed in the relaxation parameters of several preserved and stabilized tissue samples. The most dramatic changes observed throughout these experiments relate to the long-lived magnetization components, and are not observed in in vitro experiments performed solely on necrotic tissues. Meaningful differentiation between normal and neoplastic tissue by NMR techniques is virtually useless unless the roles of the temperature and necrosis on the different magnetization-decay components are well understood.