Anisotropic analysis of multi‐component T2 and T1ρ relaxations in achilles tendon by NMR spectroscopy and microscopic MRI

Abstract

To study the anisotropic characteristics of both multi-component T2 and T1ρ relaxation times in tendon. 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. 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. 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.