In Vivo sodium multiple quantum spectroscopy of human articular cartilage

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Abstract
The authors report, for the first time, sodium properties of human articular cartilage in vivo using sodium multiple‐quantum‐filtered methods with a surface coil. A flip angle‐independent, phase‐cycled pulse sequence was used to obtain triple‐quantum‐filtered spectra as a function of preparation time. Biexponential relaxation rates were calculated by fitting the triple‐quantum‐filtered spectral amplitudes to a theoretical expression. Theoretical analysis of the flip angle dependence of even rank two‐quantum coherence (T22), odd rank two‐quantum coherence (T23), and triple‐quantum coherence are presented and verified against experimental results on a cartilage specimen. Sodium multiple‐quantum‐filtered spectral lineshapes obtained in vivo correlate well with those observed on in vivo specimens. Relaxation rates obtained from asymptomatic volunteers were found to be: T2rise= 1.0 ± 0.12 ms, T2decay= 12.0 ± 0.75 ms (mean ± SD). The diagnostic potential of this method in detecting early changes in articular cartilage is described.