PURPOSE: To study the anisotropic characteristics of both multi-component T2 and T1ρ relaxation times in tendon. MATERIALS AND METHODS: T2 and T1ρ were measured in tendon by NMR spectroscopy at different orientations and by microscopic MRI at the magic angle. Several experimental issues in the multi-component relaxation measurements were investigated, including the effects of echo spacing, the resolution of MRI experiments, the influence of the specimen orientations, and the strengths of different spin-lock frequencies in T1ρ experiments. RESULTS: Both the values and fractions of T2 in tendon showed significant orientational dependence. The values and fractions of T1ρ strongly depended on both the specimen orientation and the spin-lock strength. The imaging resolution (35-280 μm) had little influence in the T2 experiments. Both the echo spacings (0.6-3.0 ms) in the T2 experiment and the spin-lock strengths (0.5-5 kHz) in the T1ρ experiment affected the quantification of the multi-component relaxation. Up to three T2 and T1ρ components were resolved in tendon. CONCLUSION: Multi-component relaxations could be attributed to different populations of water in the tissue. The transitions between a mono-component and multi-component result call for the caution in interpreting the relaxation results.
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Wang et al. (2013) studied this question.
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