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The time it takes for a proton that has been stimulated by radiofrequency (RF) energy to relax back into its usual alignment in tissue. Each tissue in the body has its own distinguishing relaxation time and its own distinctive energy emission after stimulation with RF energy. These physical characteristics of tissues are exploited in magnetic resonance imaging to create pictures of body structures.Synonym: longitudinal relaxation time; spin lattice relaxation time
See also: time